CVE-2024-39276

MEDIUM
Published Jun 25, 2024 Modified Mar 24, 2025

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.

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CVSS v3.1 Score

5.5
MEDIUM
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Affected Products

Vendor Product
linux linux_kernel
linux linux_kernel
linux linux_kernel
linux linux_kernel
linux linux_kernel
linux linux_kernel
linux linux_kernel

References

Advisories & Patches

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

Frequently Asked Questions

What is CVE-2024-39276? +
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. It has a CVSS v3.1 base score of 5.5 (MEDIUM).
How severe is CVE-2024-39276? +
CVE-2024-39276 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.
What products are affected by CVE-2024-39276? +
CVE-2024-39276 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.
How do I check if I'm vulnerable to CVE-2024-39276? +
You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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