Summary

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

Original description

The description as published by the source.

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.

Source: OSV.dev (Open Source Vulnerabilities) NVD OSV

Affected packages

Linux Kernel

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"4.19.316"}]},{"type":"ECOSYSTEM","events":[{"introduced":"4.20.0"},{"fixed":"5.4.278"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.0.0"},{"fixed":"5.10.219"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.5.0"},{"fixed":"5.15.161"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"6.1.94"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.6.34"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.9.5"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

Debian DEBIAN-CVE-2024-39276 linux Fixed in: 5.10.221-1
Ubuntu UBUNTU-CVE-2024-39276 linux-azure