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Unrated severityNVD Advisory· Published Jun 25, 2024· Updated May 4, 2025

ext4: fix mb_cache_entry's e_refcnt leak in ext4_xattr_block_cache_find()

CVE-2024-39276

Description

In the Linux kernel, the following vulnerability has been resolved:

ext4: fix mb_cache_entry's e_refcnt leak in ext4_xattr_block_cache_find()

Syzbot reports a warning as follows:

============================================ WARNING: CPU: 0 PID: 5075 at fs/mbcache.c:419 mb_cache_destroy+0x224/0x290 Modules linked in: CPU: 0 PID: 5075 Comm: syz-executor199 Not tainted 6.9.0-rc6-gb947cc5bf6d7 RIP: 0010:mb_cache_destroy+0x224/0x290 fs/mbcache.c:419 Call Trace:

ext4_put_super+0x6d4/0xcd0 fs/ext4/super.c:1375 generic_shutdown_super+0x136/0x2d0 fs/super.c:641 kill_block_super+0x44/0x90 fs/super.c:1675 ext4_kill_sb+0x68/0xa0 fs/ext4/super.c:7327 [...] ============================================

This is because when finding an entry in ext4_xattr_block_cache_find(), if ext4_sb_bread() returns -ENOMEM, the ce's e_refcnt, which has already grown in the __entry_find(), won't be put away, and eventually trigger the above issue in mb_cache_destroy() due to reference count leakage.

So call mb_cache_entry_put() on the -ENOMEM error branch as a quick fix.

Affected products

121

Patches

8
681ff9a09acc
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.gitvia osv
commit
76dc776153a4
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.gitvia osv
commit
896a7e7d0d55
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.gitvia osv
commit
a95df6f04f2c
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.gitvia osv
commit
e941b712e758
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.gitvia osv
commit
0c0b4a49d3e7
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.gitvia osv
commit
b37c0edef4e6
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.gitvia osv
commit
9ad75e78747b
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.gitvia osv
commit

Vulnerability mechanics

Generated on May 9, 2026. Inputs: CWE entries + fix-commit diffs from this CVE's patches. Citations validated against bundle.

References

8

News mentions

0

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