CVE-2024-49870 Information

Description

In the Linux kernel the following vulnerability has been resolved:

cachefiles: fix dentry leak in cachefiles_open_file()

A dentry leak may be caused when a lookup cookie and a cull are concurrent:

        P1             |             P2

cachefiles_lookup_cookie cachefiles_look_up_object lookup_one_positive_unlocked // get dentry cachefiles_cull inode->i_flags |= S_KERNEL_FILE; cachefiles_open_file cachefiles_mark_inode_in_use __cachefiles_mark_inode_in_use can_use = false if (!(inode->i_flags & S_KERNEL_FILE)) can_use = true return false return false // Returns an error but doesn’t put dentry

After that the following WARNING will be triggered when the backend folder is umounted:

================================================================== BUG: Dentry 000000008ad87947i=7an=Dx_1_1.img still in use (1) [unmount of ext4 sda] WARNING: CPU: 4 PID: 359261 at fs/dcache.c:1767 umount_check+0x5d/0x70 CPU: 4 PID: 359261 Comm: umount Not tainted 6.6.0-dirty 25 RIP: 0010:umount_check+0x5d/0x70 Call Trace: d_walk+0xda/0x2b0 do_one_tree+0x20/0x40 shrink_dcache_for_umount+0x2c/0x90 generic_shutdown_super+0x20/0x160 kill_block_super+0x1a/0x40 ext4_kill_sb+0x22/0x40 deactivate_locked_super+0x35/0x80 cleanup_mnt+0x104/0x160

Whether cachefiles_open_file() returns true or false the reference count obtained by lookup_positive_unlocked() in cachefiles_look_up_object() should be released.

Therefore release that reference count in cachefiles_look_up_object() to fix the above issue and simplify the code.

CVSS Vector

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

Reference

https://git.kernel.org/stable/c/d32ff64c872d7e08e893c32ba6a2374583444410 https://git.kernel.org/stable/c/c7d10fa7d7691558ff967668494672415f5fa151 https://git.kernel.org/stable/c/e4a28489b310339b2b8187bec0a437709be551c1 https://git.kernel.org/stable/c/7fa2382f97421978514a419c93054eca69f5247b https://git.kernel.org/stable/c/da6ef2dffe6056aad3435e6cf7c6471c2a62187c

Attack Complexity

LOW

Privileges Required

LOW

User Interaction Required

LOW

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

NONE

Availability Impact

NONE

Base Score

HIGH

Base Severity

5.5