CVE-2021-47118

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2021-47118", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2024-03-04T18:12:48.838Z", "datePublished": "2024-03-15T20:14:25.116Z", "dateUpdated": "2026-05-11T13:48:23.853Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-05-11T13:48:23.853Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\npid: take a reference when initializing `cad_pid`\n\nDuring boot, kernel_init_freeable() initializes `cad_pid` to the init\ntask's struct pid. Later on, we may change `cad_pid` via a sysctl, and\nwhen this happens proc_do_cad_pid() will increment the refcount on the\nnew pid via get_pid(), and will decrement the refcount on the old pid\nvia put_pid(). As we never called get_pid() when we initialized\n`cad_pid`, we decrement a reference we never incremented, can therefore\nfree the init task's struct pid early. As there can be dangling\nreferences to the struct pid, we can later encounter a use-after-free\n(e.g. when delivering signals).\n\nThis was spotted when fuzzing v5.13-rc3 with Syzkaller, but seems to\nhave been around since the conversion of `cad_pid` to struct pid in\ncommit 9ec52099e4b8 (\"[PATCH] replace cad_pid by a struct pid\") from the\npre-KASAN stone age of v2.6.19.\n\nFix this by getting a reference to the init task's struct pid when we\nassign it to `cad_pid`.\n\nFull KASAN splat below.\n\n ==================================================================\n BUG: KASAN: use-after-free in ns_of_pid include/linux/pid.h:153 [inline]\n BUG: KASAN: use-after-free in task_active_pid_ns+0xc0/0xc8 kernel/pid.c:509\n Read of size 4 at addr ffff23794dda0004 by task syz-executor.0/273\n\n CPU: 1 PID: 273 Comm: syz-executor.0 Not tainted 5.12.0-00001-g9aef892b2d15 #1\n Hardware name: linux,dummy-virt (DT)\n Call trace:\n ns_of_pid include/linux/pid.h:153 [inline]\n task_active_pid_ns+0xc0/0xc8 kernel/pid.c:509\n do_notify_parent+0x308/0xe60 kernel/signal.c:1950\n exit_notify kernel/exit.c:682 [inline]\n do_exit+0x2334/0x2bd0 kernel/exit.c:845\n do_group_exit+0x108/0x2c8 kernel/exit.c:922\n get_signal+0x4e4/0x2a88 kernel/signal.c:2781\n do_signal arch/arm64/kernel/signal.c:882 [inline]\n do_notify_resume+0x300/0x970 arch/arm64/kernel/signal.c:936\n work_pending+0xc/0x2dc\n\n Allocated by task 0:\n slab_post_alloc_hook+0x50/0x5c0 mm/slab.h:516\n slab_alloc_node mm/slub.c:2907 [inline]\n slab_alloc mm/slub.c:2915 [inline]\n kmem_cache_alloc+0x1f4/0x4c0 mm/slub.c:2920\n alloc_pid+0xdc/0xc00 kernel/pid.c:180\n copy_process+0x2794/0x5e18 kernel/fork.c:2129\n kernel_clone+0x194/0x13c8 kernel/fork.c:2500\n kernel_thread+0xd4/0x110 kernel/fork.c:2552\n rest_init+0x44/0x4a0 init/main.c:687\n arch_call_rest_init+0x1c/0x28\n start_kernel+0x520/0x554 init/main.c:1064\n 0x0\n\n Freed by task 270:\n slab_free_hook mm/slub.c:1562 [inline]\n slab_free_freelist_hook+0x98/0x260 mm/slub.c:1600\n slab_free mm/slub.c:3161 [inline]\n kmem_cache_free+0x224/0x8e0 mm/slub.c:3177\n put_pid.part.4+0xe0/0x1a8 kernel/pid.c:114\n put_pid+0x30/0x48 kernel/pid.c:109\n proc_do_cad_pid+0x190/0x1b0 kernel/sysctl.c:1401\n proc_sys_call_handler+0x338/0x4b0 fs/proc/proc_sysctl.c:591\n proc_sys_write+0x34/0x48 fs/proc/proc_sysctl.c:617\n call_write_iter include/linux/fs.h:1977 [inline]\n new_sync_write+0x3ac/0x510 fs/read_write.c:518\n vfs_write fs/read_write.c:605 [inline]\n vfs_write+0x9c4/0x1018 fs/read_write.c:585\n ksys_write+0x124/0x240 fs/read_write.c:658\n __do_sys_write fs/read_write.c:670 [inline]\n __se_sys_write fs/read_write.c:667 [inline]\n __arm64_sys_write+0x78/0xb0 fs/read_write.c:667\n __invoke_syscall arch/arm64/kernel/syscall.c:37 [inline]\n invoke_syscall arch/arm64/kernel/syscall.c:49 [inline]\n el0_svc_common.constprop.1+0x16c/0x388 arch/arm64/kernel/syscall.c:129\n do_el0_svc+0xf8/0x150 arch/arm64/kernel/syscall.c:168\n el0_svc+0x28/0x38 arch/arm64/kernel/entry-common.c:416\n el0_sync_handler+0x134/0x180 arch/arm64/kernel/entry-common.c:432\n el0_sync+0x154/0x180 arch/arm64/kernel/entry.S:701\n\n The buggy address belongs to the object at ffff23794dda0000\n which belongs to the cache pid of size 224\n The buggy address is located 4 bytes inside of\n 224-byte region [ff\n---truncated---"}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["init/main.c"], "versions": [{"version": "9ec52099e4b8678a60e9f93e41ad87885d64f3e6", "lessThan": "764c2e892d1fe895392aff62fb353fdce43bb529", "status": "affected", "versionType": "git"}, {"version": "9ec52099e4b8678a60e9f93e41ad87885d64f3e6", "lessThan": "f86c80515a8a3703e0ca2e56deb50fc2879c5ea4", "status": "affected", "versionType": "git"}, {"version": "9ec52099e4b8678a60e9f93e41ad87885d64f3e6", "lessThan": "4dbd8808a591b49b717862e6e0081bcf14a87788", "status": "affected", "versionType": "git"}, {"version": "9ec52099e4b8678a60e9f93e41ad87885d64f3e6", "lessThan": "d106f05432e60f9f62d456ef017687f5c73cb414", "status": "affected", "versionType": "git"}, {"version": "9ec52099e4b8678a60e9f93e41ad87885d64f3e6", "lessThan": "2cd6eedfa6344f5ef5c3dac3aee57a39b5b46dff", "status": "affected", "versionType": "git"}, {"version": "9ec52099e4b8678a60e9f93e41ad87885d64f3e6", "lessThan": "7178be006d495ffb741c329012da289b62dddfe6", "status": "affected", "versionType": "git"}, {"version": "9ec52099e4b8678a60e9f93e41ad87885d64f3e6", "lessThan": "b8ff869f20152fbe66b6c2e2715d26a2f9897cca", "status": "affected", "versionType": "git"}, {"version": "9ec52099e4b8678a60e9f93e41ad87885d64f3e6", "lessThan": "0711f0d7050b9e07c44bc159bbc64ac0a1022c7f", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["init/main.c"], "versions": [{"version": "2.6.19", "status": "affected"}, {"version": "0", "lessThan": "2.6.19", "status": "unaffected", "versionType": "semver"}, {"version": "4.4.272", "lessThanOrEqual": "4.4.*", "status": "unaffected", "versionType": "semver"}, {"version": "4.9.272", "lessThanOrEqual": "4.9.*", "status": "unaffected", "versionType": "semver"}, {"version": "4.14.236", "lessThanOrEqual": "4.14.*", "status": "unaffected", "versionType": "semver"}, {"version": "4.19.194", "lessThanOrEqual": "4.19.*", "status": "unaffected", "versionType": "semver"}, {"version": "5.4.125", "lessThanOrEqual": "5.4.*", "status": "unaffected", "versionType": "semver"}, {"version": "5.10.43", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver"}, {"version": "5.12.10", "lessThanOrEqual": "5.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "5.13", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix"}]}], "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.19", "versionEndExcluding": "4.4.272"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.19", "versionEndExcluding": "4.9.272"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.19", "versionEndExcluding": "4.14.236"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.19", "versionEndExcluding": "4.19.194"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "2.6.19", "versionEndExcluding": "5.4.125"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", 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"https://git.kernel.org/stable/c/0711f0d7050b9e07c44bc159bbc64ac0a1022c7f"}], "title": "pid: take a reference when initializing `cad_pid`", "x_generator": {"engine": "bippy-1.2.0"}}, "adp": [{"providerMetadata": {"orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2024-08-04T05:24:39.826Z"}, "title": "CVE Program Container", "references": [{"url": "https://git.kernel.org/stable/c/764c2e892d1fe895392aff62fb353fdce43bb529", "tags": ["x_transferred"]}, {"url": "https://git.kernel.org/stable/c/f86c80515a8a3703e0ca2e56deb50fc2879c5ea4", "tags": ["x_transferred"]}, {"url": "https://git.kernel.org/stable/c/4dbd8808a591b49b717862e6e0081bcf14a87788", "tags": ["x_transferred"]}, {"url": "https://git.kernel.org/stable/c/d106f05432e60f9f62d456ef017687f5c73cb414", "tags": ["x_transferred"]}, {"url": "https://git.kernel.org/stable/c/2cd6eedfa6344f5ef5c3dac3aee57a39b5b46dff", "tags": ["x_transferred"]}, {"url": 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{"engine": "bippy-5f407fcff5a0"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\npid: take a reference when initializing `cad_pid`\n\nDuring boot, kernel_init_freeable() initializes `cad_pid` to the init\ntask's struct pid. Later on, we may change `cad_pid` via a sysctl, and\nwhen this happens proc_do_cad_pid() will increment the refcount on the\nnew pid via get_pid(), and will decrement the refcount on the old pid\nvia put_pid(). As we never called get_pid() when we initialized\n`cad_pid`, we decrement a reference we never incremented, can therefore\nfree the init task's struct pid early. As there can be dangling\nreferences to the struct pid, we can later encounter a use-after-free\n(e.g. when delivering signals).\n\nThis was spotted when fuzzing v5.13-rc3 with Syzkaller, but seems to\nhave been around since the conversion of `cad_pid` to struct pid in\ncommit 9ec52099e4b8 (\"[PATCH] replace cad_pid by a struct pid\") from the\npre-KASAN stone age of v2.6.19.\n\nFix this by getting a reference to the init task's struct pid when we\nassign it to `cad_pid`.\n\nFull KASAN splat below.\n\n ==================================================================\n BUG: KASAN: use-after-free in ns_of_pid include/linux/pid.h:153 [inline]\n BUG: KASAN: use-after-free in task_active_pid_ns+0xc0/0xc8 kernel/pid.c:509\n Read of size 4 at addr ffff23794dda0004 by task syz-executor.0/273\n\n CPU: 1 PID: 273 Comm: syz-executor.0 Not tainted 5.12.0-00001-g9aef892b2d15 #1\n Hardware name: linux,dummy-virt (DT)\n Call trace:\n ns_of_pid include/linux/pid.h:153 [inline]\n task_active_pid_ns+0xc0/0xc8 kernel/pid.c:509\n do_notify_parent+0x308/0xe60 kernel/signal.c:1950\n exit_notify kernel/exit.c:682 [inline]\n do_exit+0x2334/0x2bd0 kernel/exit.c:845\n do_group_exit+0x108/0x2c8 kernel/exit.c:922\n get_signal+0x4e4/0x2a88 kernel/signal.c:2781\n do_signal arch/arm64/kernel/signal.c:882 [inline]\n do_notify_resume+0x300/0x970 arch/arm64/kernel/signal.c:936\n work_pending+0xc/0x2dc\n\n Allocated by task 0:\n slab_post_alloc_hook+0x50/0x5c0 mm/slab.h:516\n slab_alloc_node mm/slub.c:2907 [inline]\n slab_alloc mm/slub.c:2915 [inline]\n kmem_cache_alloc+0x1f4/0x4c0 mm/slub.c:2920\n alloc_pid+0xdc/0xc00 kernel/pid.c:180\n copy_process+0x2794/0x5e18 kernel/fork.c:2129\n kernel_clone+0x194/0x13c8 kernel/fork.c:2500\n kernel_thread+0xd4/0x110 kernel/fork.c:2552\n rest_init+0x44/0x4a0 init/main.c:687\n arch_call_rest_init+0x1c/0x28\n start_kernel+0x520/0x554 init/main.c:1064\n 0x0\n\n Freed by task 270:\n slab_free_hook mm/slub.c:1562 [inline]\n slab_free_freelist_hook+0x98/0x260 mm/slub.c:1600\n slab_free mm/slub.c:3161 [inline]\n kmem_cache_free+0x224/0x8e0 mm/slub.c:3177\n put_pid.part.4+0xe0/0x1a8 kernel/pid.c:114\n put_pid+0x30/0x48 kernel/pid.c:109\n proc_do_cad_pid+0x190/0x1b0 kernel/sysctl.c:1401\n proc_sys_call_handler+0x338/0x4b0 fs/proc/proc_sysctl.c:591\n proc_sys_write+0x34/0x48 fs/proc/proc_sysctl.c:617\n call_write_iter include/linux/fs.h:1977 [inline]\n new_sync_write+0x3ac/0x510 fs/read_write.c:518\n vfs_write fs/read_write.c:605 [inline]\n vfs_write+0x9c4/0x1018 fs/read_write.c:585\n ksys_write+0x124/0x240 fs/read_write.c:658\n __do_sys_write fs/read_write.c:670 [inline]\n __se_sys_write fs/read_write.c:667 [inline]\n __arm64_sys_write+0x78/0xb0 fs/read_write.c:667\n __invoke_syscall arch/arm64/kernel/syscall.c:37 [inline]\n invoke_syscall arch/arm64/kernel/syscall.c:49 [inline]\n el0_svc_common.constprop.1+0x16c/0x388 arch/arm64/kernel/syscall.c:129\n do_el0_svc+0xf8/0x150 arch/arm64/kernel/syscall.c:168\n el0_svc+0x28/0x38 arch/arm64/kernel/entry-common.c:416\n el0_sync_handler+0x134/0x180 arch/arm64/kernel/entry-common.c:432\n el0_sync+0x154/0x180 arch/arm64/kernel/entry.S:701\n\n The buggy address belongs to the object at ffff23794dda0000\n which belongs to the cache pid of size 224\n The buggy address is located 4 bytes inside of\n 224-byte region [ff\n---truncated---"}], "providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2024-12-19T07:35:33.871Z"}}}, "cveMetadata": {"cveId": "CVE-2021-47118", "state": "PUBLISHED", "dateUpdated": "2024-12-19T07:35:33.871Z", "dateReserved": "2024-03-04T18:12:48.838Z", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "datePublished": "2024-03-15T20:14:25.116Z", "assignerShortName": "Linux"}, "dataVersion": "5.1"}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["init/main.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "764c2e892d1fe895392aff62fb353fdce43bb529", "status": "affected", "version": "9ec52099e4b8678a60e9f93e41ad87885d64f3e6", "versionType": "git"}, {"lessThan": "f86c80515a8a3703e0ca2e56deb50fc2879c5ea4", "status": "affected", "version": "9ec52099e4b8678a60e9f93e41ad87885d64f3e6", "versionType": "git"}, {"lessThan": "4dbd8808a591b49b717862e6e0081bcf14a87788", "status": "affected", "version": "9ec52099e4b8678a60e9f93e41ad87885d64f3e6", "versionType": "git"}, {"lessThan": "d106f05432e60f9f62d456ef017687f5c73cb414", "status": "affected", "version": "9ec52099e4b8678a60e9f93e41ad87885d64f3e6", "versionType": "git"}, {"lessThan": "2cd6eedfa6344f5ef5c3dac3aee57a39b5b46dff", "status": "affected", "version": "9ec52099e4b8678a60e9f93e41ad87885d64f3e6", "versionType": "git"}, {"lessThan": "7178be006d495ffb741c329012da289b62dddfe6", "status": "affected", "version": "9ec52099e4b8678a60e9f93e41ad87885d64f3e6", "versionType": "git"}, {"lessThan": "b8ff869f20152fbe66b6c2e2715d26a2f9897cca", "status": "affected", "version": "9ec52099e4b8678a60e9f93e41ad87885d64f3e6", "versionType": "git"}, {"lessThan": "0711f0d7050b9e07c44bc159bbc64ac0a1022c7f", "status": "affected", "version": "9ec52099e4b8678a60e9f93e41ad87885d64f3e6", "versionType": "git"}]}, {"defaultStatus": "affected", "product": "Linux", "programFiles": ["init/main.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"status": "affected", "version": "2.6.19"}, {"lessThan": "2.6.19", "status": "unaffected", "version": "0", "versionType": "semver"}, {"lessThanOrEqual": "4.4.*", "status": "unaffected", "version": "4.4.272", "versionType": "semver"}, {"lessThanOrEqual": "4.9.*", "status": "unaffected", "version": "4.9.272", "versionType": "semver"}, {"lessThanOrEqual": "4.14.*", "status": "unaffected", "version": "4.14.236", "versionType": "semver"}, {"lessThanOrEqual": "4.19.*", "status": "unaffected", "version": "4.19.194", "versionType": "semver"}, {"lessThanOrEqual": "5.4.*", "status": "unaffected", "version": "5.4.125", "versionType": "semver"}, {"lessThanOrEqual": "5.10.*", "status": "unaffected", "version": "5.10.43", "versionType": "semver"}, {"lessThanOrEqual": "5.12.*", "status": "unaffected", "version": "5.12.10", "versionType": "semver"}, {"lessThanOrEqual": "*", "status": "unaffected", "version": "5.13", "versionType": "original_commit_for_fix"}]}], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "29036811-1F9B-4A08-8FE1-0E5D46AB14FA", "versionEndExcluding": "4.4.272", "versionStartIncluding": "2.6.19", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "8FEC5189-264E-4620-BD41-8B5E44F20D80", "versionEndExcluding": "4.9.272", "versionStartIncluding": "4.5", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "32BD3098-E25B-4893-87B7-49DAAD61B503", "versionEndExcluding": "4.14.236", "versionStartIncluding": "4.10", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "219AB3A3-BDC8-47F5-A638-4A3D5D451EC3", "versionEndExcluding": "4.19.194", "versionStartIncluding": "4.15", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "552FBD6A-793D-4EE1-9D44-69978256AA46", "versionEndExcluding": "5.4.125", "versionStartIncluding": "4.20", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "B2136BD5-4F86-40C8-96C8-5C90A015490C", "versionEndExcluding": "5.10.43", "versionStartIncluding": "5.5", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "27384800-AB48-4C08-891E-34B66F5FC4AA", "versionEndExcluding": "5.12.10", "versionStartIncluding": "5.11", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:5.13:rc1:*:*:*:*:*:*", "matchCriteriaId": "0CBAD0FC-C281-4666-AB2F-F8E6E1165DF7", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:5.13:rc2:*:*:*:*:*:*", "matchCriteriaId": "96AC23B2-D46A-49D9-8203-8E1BEDCA8532", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:5.13:rc3:*:*:*:*:*:*", "matchCriteriaId": "DA610E30-717C-4700-9F77-A3C9244F3BFD", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:5.13:rc4:*:*:*:*:*:*", "matchCriteriaId": "1ECD33F5-85BE-430B-8F86-8D7BD560311D", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\npid: take a reference when initializing `cad_pid`\n\nDuring boot, kernel_init_freeable() initializes `cad_pid` to the init\ntask's struct pid. Later on, we may change `cad_pid` via a sysctl, and\nwhen this happens proc_do_cad_pid() will increment the refcount on the\nnew pid via get_pid(), and will decrement the refcount on the old pid\nvia put_pid(). As we never called get_pid() when we initialized\n`cad_pid`, we decrement a reference we never incremented, can therefore\nfree the init task's struct pid early. As there can be dangling\nreferences to the struct pid, we can later encounter a use-after-free\n(e.g. when delivering signals).\n\nThis was spotted when fuzzing v5.13-rc3 with Syzkaller, but seems to\nhave been around since the conversion of `cad_pid` to struct pid in\ncommit 9ec52099e4b8 (\"[PATCH] replace cad_pid by a struct pid\") from the\npre-KASAN stone age of v2.6.19.\n\nFix this by getting a reference to the init task's struct pid when we\nassign it to `cad_pid`.\n\nFull KASAN splat below.\n\n ==================================================================\n BUG: KASAN: use-after-free in ns_of_pid include/linux/pid.h:153 [inline]\n BUG: KASAN: use-after-free in task_active_pid_ns+0xc0/0xc8 kernel/pid.c:509\n Read of size 4 at addr ffff23794dda0004 by task syz-executor.0/273\n\n CPU: 1 PID: 273 Comm: syz-executor.0 Not tainted 5.12.0-00001-g9aef892b2d15 #1\n Hardware name: linux,dummy-virt (DT)\n Call trace:\n ns_of_pid include/linux/pid.h:153 [inline]\n task_active_pid_ns+0xc0/0xc8 kernel/pid.c:509\n do_notify_parent+0x308/0xe60 kernel/signal.c:1950\n exit_notify kernel/exit.c:682 [inline]\n do_exit+0x2334/0x2bd0 kernel/exit.c:845\n do_group_exit+0x108/0x2c8 kernel/exit.c:922\n get_signal+0x4e4/0x2a88 kernel/signal.c:2781\n do_signal arch/arm64/kernel/signal.c:882 [inline]\n do_notify_resume+0x300/0x970 arch/arm64/kernel/signal.c:936\n work_pending+0xc/0x2dc\n\n Allocated by task 0:\n slab_post_alloc_hook+0x50/0x5c0 mm/slab.h:516\n slab_alloc_node mm/slub.c:2907 [inline]\n slab_alloc mm/slub.c:2915 [inline]\n kmem_cache_alloc+0x1f4/0x4c0 mm/slub.c:2920\n alloc_pid+0xdc/0xc00 kernel/pid.c:180\n copy_process+0x2794/0x5e18 kernel/fork.c:2129\n kernel_clone+0x194/0x13c8 kernel/fork.c:2500\n kernel_thread+0xd4/0x110 kernel/fork.c:2552\n rest_init+0x44/0x4a0 init/main.c:687\n arch_call_rest_init+0x1c/0x28\n start_kernel+0x520/0x554 init/main.c:1064\n 0x0\n\n Freed by task 270:\n slab_free_hook mm/slub.c:1562 [inline]\n slab_free_freelist_hook+0x98/0x260 mm/slub.c:1600\n slab_free mm/slub.c:3161 [inline]\n kmem_cache_free+0x224/0x8e0 mm/slub.c:3177\n put_pid.part.4+0xe0/0x1a8 kernel/pid.c:114\n put_pid+0x30/0x48 kernel/pid.c:109\n proc_do_cad_pid+0x190/0x1b0 kernel/sysctl.c:1401\n proc_sys_call_handler+0x338/0x4b0 fs/proc/proc_sysctl.c:591\n proc_sys_write+0x34/0x48 fs/proc/proc_sysctl.c:617\n call_write_iter include/linux/fs.h:1977 [inline]\n new_sync_write+0x3ac/0x510 fs/read_write.c:518\n vfs_write fs/read_write.c:605 [inline]\n vfs_write+0x9c4/0x1018 fs/read_write.c:585\n ksys_write+0x124/0x240 fs/read_write.c:658\n __do_sys_write fs/read_write.c:670 [inline]\n __se_sys_write fs/read_write.c:667 [inline]\n __arm64_sys_write+0x78/0xb0 fs/read_write.c:667\n __invoke_syscall arch/arm64/kernel/syscall.c:37 [inline]\n invoke_syscall arch/arm64/kernel/syscall.c:49 [inline]\n el0_svc_common.constprop.1+0x16c/0x388 arch/arm64/kernel/syscall.c:129\n do_el0_svc+0xf8/0x150 arch/arm64/kernel/syscall.c:168\n el0_svc+0x28/0x38 arch/arm64/kernel/entry-common.c:416\n el0_sync_handler+0x134/0x180 arch/arm64/kernel/entry-common.c:432\n el0_sync+0x154/0x180 arch/arm64/kernel/entry.S:701\n\n The buggy address belongs to the object at ffff23794dda0000\n which belongs to the cache pid of size 224\n The buggy address is located 4 bytes inside of\n 224-byte region [ff\n---truncated---"}, {"lang": "es", "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: pid: toma una referencia al inicializar `cad_pid` Durante el arranque, kernel_init_freeable() inicializa `cad_pid` en la estructura pid de la tarea de inicio. M\u00e1s adelante, podemos cambiar `cad_pid` mediante un sysctl, y cuando esto suceda, proc_do_cad_pid() incrementar\u00e1 el recuento en el nuevo pid mediante get_pid(), y disminuir\u00e1 el recuento en el pid antiguo mediante put_pid(). Como nunca llamamos a get_pid() cuando inicializamos `cad_pid`, disminuimos una referencia que nunca incrementamos, por lo que podemos liberar la estructura pid de la tarea de inicio antes. Como puede haber referencias pendientes a la estructura pid, m\u00e1s adelante podemos encontrarnos con un use-after-free (por ejemplo, al entregar se\u00f1ales). Esto se detect\u00f3 al fusionar v5.13-rc3 con Syzkaller, pero parece haber existido desde la conversi\u00f3n de `cad_pid` a struct pid en el commit 9ec52099e4b8 (\"[PATCH] reemplaza cad_pid por una estructura pid\") del pre-KASAN edad de piedra de v2.6.19. Solucione este problema obteniendo una referencia a la estructura pid de la tarea de inicio cuando la asignamos a `cad_pid`. S\u00edmbolo completo de KASAN a continuaci\u00f3n. ==================================================== ================ ERROR: KASAN: use-after-free en ns_of_pid include/linux/pid.h:153 [en l\u00ednea] ERROR: KASAN: use-after-free en task_active_pid_ns +0xc0/0xc8 kernel/pid.c:509 Lectura de tama\u00f1o 4 en addr ffff23794dda0004 por tarea syz-executor.0/273 CPU: 1 PID: 273 Comm: syz-executor.0 No contaminado 5.12.0-00001-g9aef892b2d15 # 1 Nombre del hardware: linux,dummy-virt (DT) Rastreo de llamadas: ns_of_pid include/linux/pid.h:153 [en l\u00ednea] task_active_pid_ns+0xc0/0xc8 kernel/pid.c:509 do_notify_parent+0x308/0xe60 kernel/signal.c :1950 exit_notify kernel/exit.c:682 [en l\u00ednea] do_exit+0x2334/0x2bd0 kernel/exit.c:845 do_group_exit+0x108/0x2c8 kernel/exit.c:922 get_signal+0x4e4/0x2a88 kernel/signal.c:2781 do_signal arch/arm64/kernel/signal.c:882 [en l\u00ednea] do_notify_resume+0x300/0x970 arch/arm64/kernel/signal.c:936 work_pending+0xc/0x2dc Asignado por tarea 0: slab_post_alloc_hook+0x50/0x5c0 mm/slab.h :516 slab_alloc_node mm/slub.c:2907 [en l\u00ednea] slab_alloc mm/slub.c:2915 [en l\u00ednea] kmem_cache_alloc+0x1f4/0x4c0 mm/slub.c:2920 alloc_pid+0xdc/0xc00 kernel/pid.c:180 copy_process+ 0x2794/0x5e18 kernel/fork.c:2129 kernel_clone+0x194/0x13c8 kernel/fork.c:2500 kernel_thread+0xd4/0x110 kernel/fork.c:2552 rest_init+0x44/0x4a0 init/main.c:687 arch_call_rest_init+0x1c/ 0x28 start_kernel+0x520/0x554 init/main.c:1064 0x0 Liberado por la tarea 270: slab_free_hook mm/slub.c:1562 [en l\u00ednea] slab_free_freelist_hook+0x98/0x260 mm/slub.c:1600 slab_free mm/slub.c:3161 [en l\u00ednea] kmem_cache_free+0x224/0x8e0 mm/slub.c:3177 put_pid.part.4+0xe0/0x1a8 kernel/pid.c:114 put_pid+0x30/0x48 kernel/pid.c:109 proc_do_cad_pid+0x190/0x1b0 kernel/ sysctl.c:1401 proc_sys_call_handler+0x338/0x4b0 fs/proc/proc_sysctl.c:591 proc_sys_write+0x34/0x48 fs/proc/proc_sysctl.c:617 call_write_iter include/linux/fs.h:1977 [en l\u00ednea] new_sync_write+0x3ac/ 0x510 fs/read_write.c:518 vfs_write fs/read_write.c:605 [en l\u00ednea] vfs_write+0x9c4/0x1018 fs/read_write.c:585 ksys_write+0x124/0x240 fs/read_write.c:658 __do_sys_write fs/read_write.c: 670 [en l\u00ednea] __se_sys_write fs/read_write.c:667 [en l\u00ednea] __arm64_sys_write+0x78/0xb0 fs/read_write.c:667 __invoke_syscall arch/arm64/kernel/syscall.c:37 [en l\u00ednea] invoke_syscall arch/arm64/kernel/syscall .c:49 [en l\u00ednea] el0_svc_common.constprop.1+0x16c/0x388 arch/arm64/kernel/syscall.c:129 do_el0_svc+0xf8/0x150 arch/arm64/kernel/syscall.c:168 el0_svc+0x28/0x38 arch/ arm64/kernel/entry-common.c:416 el0_sync_handler+0x134/0x180 arch/arm64/kernel/entry-common.c:432 el0_sync+0x154/0x180 arch/arm64/kernel/entry.S:701 La direcci\u00f3n del error pertenece a el objeto en ffff23794dda0000 que pertenece al pid de cach\u00e9 de tama\u00f1o 224.---truncado---"}], "id": "CVE-2021-47118", "lastModified": "2026-06-17T04:16:32.340", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 7.8, "baseSeverity": "HIGH", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 5.9, "source": "nvd@nist.gov", "type": "Primary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2021-47118", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2024-09-10T15:55:32.497500Z", "version": "2.0.3"}}]}, "published": "2024-03-15T21:15:06.943", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/0711f0d7050b9e07c44bc159bbc64ac0a1022c7f"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/2cd6eedfa6344f5ef5c3dac3aee57a39b5b46dff"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/4dbd8808a591b49b717862e6e0081bcf14a87788"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/7178be006d495ffb741c329012da289b62dddfe6"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/764c2e892d1fe895392aff62fb353fdce43bb529"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/b8ff869f20152fbe66b6c2e2715d26a2f9897cca"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/d106f05432e60f9f62d456ef017687f5c73cb414"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/f86c80515a8a3703e0ca2e56deb50fc2879c5ea4"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/0711f0d7050b9e07c44bc159bbc64ac0a1022c7f"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/2cd6eedfa6344f5ef5c3dac3aee57a39b5b46dff"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/4dbd8808a591b49b717862e6e0081bcf14a87788"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/7178be006d495ffb741c329012da289b62dddfe6"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/764c2e892d1fe895392aff62fb353fdce43bb529"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/b8ff869f20152fbe66b6c2e2715d26a2f9897cca"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/d106f05432e60f9f62d456ef017687f5c73cb414"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/f86c80515a8a3703e0ca2e56deb50fc2879c5ea4"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-416"}], "source": "nvd@nist.gov", "type": "Primary"}]}

{"affected_release": [{"advisory": "RHSA-2024:3627", "cpe": "cpe:/a:redhat:enterprise_linux:8::nfv", "package": "kernel-rt-0:4.18.0-553.5.1.rt7.346.el8_10", "product_name": "Red Hat Enterprise Linux 8", "release_date": "2024-06-05T00:00:00Z"}, {"advisory": "RHSA-2024:3618", "cpe": "cpe:/o:redhat:enterprise_linux:8", "package": "kernel-0:4.18.0-553.5.1.el8_10", "product_name": "Red Hat Enterprise Linux 8", "release_date": "2024-06-05T00:00:00Z"}], "bugzilla": {"description": "kernel: pid: take a reference when initializing `cad_pid`", "id": "2269856", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2269856"}, "csaw": false, "cvss3": {"cvss3_base_score": "4.1", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H", "status": "verified"}, "cwe": "CWE-416", "details": ["In the Linux kernel, the following vulnerability has been resolved:\npid: take a reference when initializing `cad_pid`\nDuring boot, kernel_init_freeable() initializes `cad_pid` to the init\ntask's struct pid. Later on, we may change `cad_pid` via a sysctl, and\nwhen this happens proc_do_cad_pid() will increment the refcount on the\nnew pid via get_pid(), and will decrement the refcount on the old pid\nvia put_pid(). As we never called get_pid() when we initialized\n`cad_pid`, we decrement a reference we never incremented, can therefore\nfree the init task's struct pid early. As there can be dangling\nreferences to the struct pid, we can later encounter a use-after-free\n(e.g. when delivering signals).\nThis was spotted when fuzzing v5.13-rc3 with Syzkaller, but seems to\nhave been around since the conversion of `cad_pid` to struct pid in\ncommit 9ec52099e4b8 (\"[PATCH] replace cad_pid by a struct pid\") from the\npre-KASAN stone age of v2.6.19.\nFix this by getting a reference to the init task's struct pid when we\nassign it to `cad_pid`.\nFull KASAN splat below.\n==================================================================\nBUG: KASAN: use-after-free in ns_of_pid include/linux/pid.h:153 [inline]\nBUG: KASAN: use-after-free in task_active_pid_ns+0xc0/0xc8 kernel/pid.c:509\nRead of size 4 at addr ffff23794dda0004 by task syz-executor.0/273\nCPU: 1 PID: 273 Comm: syz-executor.0 Not tainted 5.12.0-00001-g9aef892b2d15 #1\nHardware name: linux,dummy-virt (DT)\nCall trace:\nns_of_pid include/linux/pid.h:153 [inline]\ntask_active_pid_ns+0xc0/0xc8 kernel/pid.c:509\ndo_notify_parent+0x308/0xe60 kernel/signal.c:1950\nexit_notify kernel/exit.c:682 [inline]\ndo_exit+0x2334/0x2bd0 kernel/exit.c:845\ndo_group_exit+0x108/0x2c8 kernel/exit.c:922\nget_signal+0x4e4/0x2a88 kernel/signal.c:2781\ndo_signal arch/arm64/kernel/signal.c:882 [inline]\ndo_notify_resume+0x300/0x970 arch/arm64/kernel/signal.c:936\nwork_pending+0xc/0x2dc\nAllocated by task 0:\nslab_post_alloc_hook+0x50/0x5c0 mm/slab.h:516\nslab_alloc_node mm/slub.c:2907 [inline]\nslab_alloc mm/slub.c:2915 [inline]\nkmem_cache_alloc+0x1f4/0x4c0 mm/slub.c:2920\nalloc_pid+0xdc/0xc00 kernel/pid.c:180\ncopy_process+0x2794/0x5e18 kernel/fork.c:2129\nkernel_clone+0x194/0x13c8 kernel/fork.c:2500\nkernel_thread+0xd4/0x110 kernel/fork.c:2552\nrest_init+0x44/0x4a0 init/main.c:687\narch_call_rest_init+0x1c/0x28\nstart_kernel+0x520/0x554 init/main.c:1064\n0x0\nFreed by task 270:\nslab_free_hook mm/slub.c:1562 [inline]\nslab_free_freelist_hook+0x98/0x260 mm/slub.c:1600\nslab_free mm/slub.c:3161 [inline]\nkmem_cache_free+0x224/0x8e0 mm/slub.c:3177\nput_pid.part.4+0xe0/0x1a8 kernel/pid.c:114\nput_pid+0x30/0x48 kernel/pid.c:109\nproc_do_cad_pid+0x190/0x1b0 kernel/sysctl.c:1401\nproc_sys_call_handler+0x338/0x4b0 fs/proc/proc_sysctl.c:591\nproc_sys_write+0x34/0x48 fs/proc/proc_sysctl.c:617\ncall_write_iter include/linux/fs.h:1977 [inline]\nnew_sync_write+0x3ac/0x510 fs/read_write.c:518\nvfs_write fs/read_write.c:605 [inline]\nvfs_write+0x9c4/0x1018 fs/read_write.c:585\nksys_write+0x124/0x240 fs/read_write.c:658\n__do_sys_write fs/read_write.c:670 [inline]\n__se_sys_write fs/read_write.c:667 [inline]\n__arm64_sys_write+0x78/0xb0 fs/read_write.c:667\n__invoke_syscall arch/arm64/kernel/syscall.c:37 [inline]\ninvoke_syscall arch/arm64/kernel/syscall.c:49 [inline]\nel0_svc_common.constprop.1+0x16c/0x388 arch/arm64/kernel/syscall.c:129\ndo_el0_svc+0xf8/0x150 arch/arm64/kernel/syscall.c:168\nel0_svc+0x28/0x38 arch/arm64/kernel/entry-common.c:416\nel0_sync_handler+0x134/0x180 arch/arm64/kernel/entry-common.c:432\nel0_sync+0x154/0x180 arch/arm64/kernel/entry.S:701\nThe buggy address belongs to the object at ffff23794dda0000\nwhich belongs to the cache pid of size 224\nThe buggy address is located 4 bytes inside of\n224-byte region [ff\n---truncated---"], "name": "CVE-2021-47118", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Out of support scope", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}], "public_date": "2024-03-15T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2021-47118\nhttps://nvd.nist.gov/vuln/detail/CVE-2021-47118\nhttps://lore.kernel.org/linux-cve-announce/2024031509-CVE-2021-47118-faf2@gregkh/T/#u"], "threat_severity": "Low"}

{}