CVE-2024-39276

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

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: <TASK> 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.

5.5

CVSS

Severity: Medium

CVSS 3.1 •

EPSS 0.04%

Affected: Linux Linux

References

Link	Tags
https://git.kernel.org/stable/c/9ad75e78747b5a50dc5a52f0f8e92e920a653f16	patch
https://git.kernel.org/stable/c/896a7e7d0d555ad8b2b46af0c2fa7de7467f9483	patch
https://git.kernel.org/stable/c/76dc776153a47372719d664e0fc50d6355791abb	patch
https://git.kernel.org/stable/c/681ff9a09accd8a4379f8bd30b7a1641ee19bb3e	patch
https://git.kernel.org/stable/c/e941b712e758f615d311946bf98216e79145ccd9	patch
https://git.kernel.org/stable/c/a95df6f04f2c37291adf26a74205cde0314d4577	patch
https://git.kernel.org/stable/c/b37c0edef4e66fb21a2fbc211471195a383e5ab8	patch
https://git.kernel.org/stable/c/0c0b4a49d3e7f49690a6827a41faeffad5df7e21	patch

Frequently Asked Questions

What is the severity of CVE-2024-39276?: CVE-2024-39276 has been scored as a medium severity vulnerability.
How to fix CVE-2024-39276?: To fix CVE-2024-39276, make sure you are using an up-to-date version of the affected component(s) by checking the vendor release notes. As for now, there are no other specific guidelines available.
Is CVE-2024-39276 being actively exploited in the wild?: As for now, there are no information to confirm that CVE-2024-39276 is being actively exploited. According to its EPSS score, there is a ~0% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
What software or system is affected by CVE-2024-39276?: CVE-2024-39276 affects Linux Linux, Linux Linux.