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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+0x224/0x290Modules linked in:CPU: 0 PID: 5075 Comm: syz-executor199 Not tainted 6.9.0-rc6-gb947cc5bf6d7RIP: 0010:mb_cache_destroy+0x224/0x290 fs/mbcache.c:419Call 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(), ifext4_sb_bread() returns -ENOMEM, the ce's e_refcnt, which has already grownin the __entry_find(), won't be put away, and eventually trigger the aboveissue in mb_cache_destroy() due to reference count leakage.So call mb_cache_entry_put() on the -ENOMEM error branch as a quick fix.

POC

Reference

No PoCs from references.

Github

- https://github.com/fkie-cad/nvd-json-data-feeds