CVE-2026-98119

netfs: break unbuffered write when netfs_alloc_subrequest() fails

Published Sep 25, 2026 CVSS 3.1 · 5.5 Medium EPSS < 1% KEV · Not listed
Description
In the Linux kernel, the following vulnerability has been resolved:

netfs: break unbuffered write when netfs_alloc_subrequest() fails

syzbot reported a null-ptr-deref below [1] following a fault injection in
netfs_alloc_subrequest(). [0]

When netfs_alloc_subrequest() fails, subreq is NULL.
Later, netfs_prepare_write() tries to initialize members of
subreq(e.g., source), the issue in [1] is triggered.

Let's handle the error of netfs_prepare_write() properly.

[0]
FAULT_INJECTION: forcing a failure.
name failslab, interval 1, probability 0, space 0, times 0
Call Trace:
netfs_alloc_subrequest+0x116/0x3f0
netfs_prepare_write+0x76/0x7b0
netfs_unbuffered_write+0x75c/0x2020
netfs_unbuffered_write_iter_locked+0x7d6/0xa80
netfs_unbuffered_write_iter+0x442/0x720
v9fs_file_write_iter+0xbf/0x100
vfs_write+0x6ac/0x1050

[1]
KASAN: null-ptr-deref in range [0x00000000000000a8-0x00000000000000af]
RIP: 0010:netfs_prepare_write+0xbc/0x7b0 fs/netfs/write_issue.c:173
Call Trace:
netfs_unbuffered_write+0x75c/0x2020 fs/netfs/direct_write.c:111
netfs_unbuffered_write_iter_locked+0x7d6/0xa80 fs/netfs/direct_write.c:290
netfs_unbuffered_write_iter+0x442/0x720 fs/netfs/direct_write.c:382
v9fs_file_write_iter+0xbf/0x100 fs/9p/vfs_file.c:409
new_sync_write fs/read_write.c:595 [inline]

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Ubuntu USN Ubuntu USN USN-9019-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-9020-1 Linux kernel vulnerabilities
History
Type Values Removed Values Added
CPEs cpe:2.3:o:linux:linux_kernel:7.3:rc1:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:7.3:rc2:*:*:*:*:*:*
Type Values Removed Values Added
Weaknesses CWE-476
Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: netfs: break unbuffered write when netfs_alloc_subrequest() fails syzbot reported a null-ptr-deref below [1] following a fault injection in netfs_alloc_subrequest(). [0] When netfs_alloc_subrequest() fails, subreq is NULL. Later, netfs_prepare_write() tries to initialize members of subreq(e.g., source), the issue in [1] is triggered. Let's handle the error of netfs_prepare_write() properly. [0] FAULT_INJECTION: forcing a failure. name failslab, interval 1, probability 0, space 0, times 0 Call Trace: netfs_alloc_subrequest+0x116/0x3f0 netfs_prepare_write+0x76/0x7b0 netfs_unbuffered_write+0x75c/0x2020 netfs_unbuffered_write_iter_locked+0x7d6/0xa80 netfs_unbuffered_write_iter+0x442/0x720 v9fs_file_write_iter+0xbf/0x100 vfs_write+0x6ac/0x1050 [1] KASAN: null-ptr-deref in range [0x00000000000000a8-0x00000000000000af] RIP: 0010:netfs_prepare_write+0xbc/0x7b0 fs/netfs/write_issue.c:173 Call Trace: netfs_unbuffered_write+0x75c/0x2020 fs/netfs/direct_write.c:111 netfs_unbuffered_write_iter_locked+0x7d6/0xa80 fs/netfs/direct_write.c:290 netfs_unbuffered_write_iter+0x442/0x720 fs/netfs/direct_write.c:382 v9fs_file_write_iter+0xbf/0x100 fs/9p/vfs_file.c:409 new_sync_write fs/read_write.c:595 [inline]
Title netfs: break unbuffered write when netfs_alloc_subrequest() fails
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
Linux
Published
Updated
Oct 19, 2026, 9:14 AM
Reserved
Sep 25, 2026, 10:25 AM
Status
Analyzed
Published
Sep 25, 2026, 11:17 AM
Modified
Oct 26, 2026, 6:36 PM
Severity
Low
Public date
Sep 25, 2026, 12:00 AM