CVE-2026-93235

f2fs: fix to zero post-EOF data when extending file size

Published Sep 24, 2026 CVSS n/a EPSS < 1% KEV · Not listed
Description
In the Linux kernel, the following vulnerability has been resolved:

f2fs: fix to zero post-EOF data when extending file size

generic/794 4s ... - output mismatch (see /share/git/fstests/results//generic/794.out.bad)
--- tests/generic/794.out 2026-06-12 08:46:32.766426241 +0800
+++ /share/git/fstests/results//generic/794.out.bad 2026-07-05 18:32:55.000000000 +0800
@@ -1,4 +1,16 @@
QA output created by 794
append_write
+FAIL: non-zero data in gap [4080,4096) after shutdown+remount
+000000 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a >ZZZZZZZZZZZZZZZZ<
+*
+001000
truncate_up
...
(Run 'diff -u /share/git/fstests/tests/generic/794.out /share/git/fstests/results//generic/794.out.bad' to see the entire diff)
Ran: generic/794
Failures: generic/794
Failed 1 of 1 tests

Steps of generic/794:
1. write 4096 bytes to file w/ 0x5a
2. use fiemap to get PBA of first block in file
3. truncate file to 4080
4. umount; write 4096 bytes to file w/ 0x5a directly via PBA; mount
5. extend filesize via
a) append 4096 from offset 4096, or
b) truncate 8192, or
c) fallocate 4096 from offset 4096
6. verify the gap is zeroed in memory [4080,4096)
7. sync range 4096 from offset 4096; shutdown -f (flush meta before shutdown)
8. umount; mount; verify [4080,4096) is zeroed or not.

When extending file size (e.g. via truncate, fallocate, or write) across an
unaligned EOF boundary, we need to ensure that post-EOF data in the partial
page is zeroed out in pagecache and marked dirty, then writeback the cache to
persist zeroed data before committing inode w/ updated i_size.

This help to prevent stale disk data beyond the previous EOF from being exposed
after remounting or crash recovery.

Since f2fs is a LFS filesystem, we only support direct write via PBA in pinfile,
and pinfile has section-aligned filesize, so in Android, there should no problem,
but for other usage in different environment, let's fix this w/ fsync_mode=strict
mount option.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4817-1 linux-6.12 security update
Debian DSA Debian DSA DSA-6528-1 linux security update
Ubuntu USN Ubuntu USN USN-9019-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-9020-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9022-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9023-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9024-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9025-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9026-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-9039-1 Linux kernel (Azure CVM) vulnerabilities
Ubuntu USN Ubuntu USN USN-9040-1 Linux kernel (Low Latency NVIDIA) vulnerabilities
Ubuntu USN Ubuntu USN USN-9066-1 Linux kernel (HWE) vulnerabilities
Ubuntu USN Ubuntu USN USN-9091-1 Linux kernel (NVIDIA Tegra) vulnerabilities
History
Type Values Removed Values Added
Weaknesses CWE-657
Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: f2fs: fix to zero post-EOF data when extending file size generic/794 4s ... - output mismatch (see /share/git/fstests/results//generic/794.out.bad) --- tests/generic/794.out 2026-06-12 08:46:32.766426241 +0800 +++ /share/git/fstests/results//generic/794.out.bad 2026-07-05 18:32:55.000000000 +0800 @@ -1,4 +1,16 @@ QA output created by 794 append_write +FAIL: non-zero data in gap [4080,4096) after shutdown+remount +000000 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a 5a >ZZZZZZZZZZZZZZZZ< +* +001000 truncate_up ... (Run 'diff -u /share/git/fstests/tests/generic/794.out /share/git/fstests/results//generic/794.out.bad' to see the entire diff) Ran: generic/794 Failures: generic/794 Failed 1 of 1 tests Steps of generic/794: 1. write 4096 bytes to file w/ 0x5a 2. use fiemap to get PBA of first block in file 3. truncate file to 4080 4. umount; write 4096 bytes to file w/ 0x5a directly via PBA; mount 5. extend filesize via a) append 4096 from offset 4096, or b) truncate 8192, or c) fallocate 4096 from offset 4096 6. verify the gap is zeroed in memory [4080,4096) 7. sync range 4096 from offset 4096; shutdown -f (flush meta before shutdown) 8. umount; mount; verify [4080,4096) is zeroed or not. When extending file size (e.g. via truncate, fallocate, or write) across an unaligned EOF boundary, we need to ensure that post-EOF data in the partial page is zeroed out in pagecache and marked dirty, then writeback the cache to persist zeroed data before committing inode w/ updated i_size. This help to prevent stale disk data beyond the previous EOF from being exposed after remounting or crash recovery. Since f2fs is a LFS filesystem, we only support direct write via PBA in pinfile, and pinfile has section-aligned filesize, so in Android, there should no problem, but for other usage in different environment, let's fix this w/ fsync_mode=strict mount option.
Title f2fs: fix to zero post-EOF data when extending file size
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, 9:07 AM
Reserved
Sep 17, 2026, 4:02 PM
Status
Received
Published
Sep 24, 2026, 4:17 PM
Modified
Oct 19, 2026, 10:17 AM