Race Condition Affecting kernel-default package, versions <6.4.0-150600.23.30.1
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
Do your applications use this vulnerable package?
In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.
Test your applications- Snyk IDSNYK-SLES156-KERNELDEFAULT-8507966
- published14 Dec 2024
- disclosed13 Dec 2024
Introduced: 13 Dec 2024
NewCVE-2024-47679 (opens in a new tab)How to fix?
Upgrade SLES:15.6 kernel-default to version 6.4.0-150600.23.30.1 or higher.
NVD Description
Note: Versions mentioned in the description apply only to the upstream kernel-default package and not the kernel-default package as distributed by SLES.
See How to fix? for SLES:15.6 relevant fixed versions and status.
In the Linux kernel, the following vulnerability has been resolved:
vfs: fix race between evice_inodes() and find_inode()&iput()
Hi, all
Recently I noticed a bug1 in btrfs, after digged it into and I believe it'a race in vfs.
Let's assume there's a inode (ie ino 261) with i_count 1 is called by iput(), and there's a concurrent thread calling generic_shutdown_super().
cpu0: cpu1: iput() // i_count is 1 ->spin_lock(inode) ->dec i_count to 0 ->iput_final() generic_shutdown_super() ->__inode_add_lru() ->evict_inodes() // cause some reason[2] ->if (atomic_read(inode->i_count)) continue; // return before // inode 261 passed the above check // list_lru_add_obj() // and then schedule out ->spin_unlock() // note here: the inode 261 // was still at sb list and hash list, // and I_FREEING|I_WILL_FREE was not been set
btrfs_iget() // after some function calls ->find_inode() // found the above inode 261 ->spin_lock(inode) // check I_FREEING|I_WILL_FREE // and passed ->__iget() ->spin_unlock(inode) // schedule back ->spin_lock(inode) // check (I_NEW|I_FREEING|I_WILL_FREE) flags, // passed and set I_FREEING iput() ->spin_unlock(inode) ->spin_lock(inode) ->evict() // dec i_count to 0 ->iput_final() ->spin_unlock() ->evict()
Now, we have two threads simultaneously evicting the same inode, which may trigger the BUG(inode->i_state & I_CLEAR) statement both within clear_inode() and iput().
To fix the bug, recheck the inode->i_count after holding i_lock. Because in the most scenarios, the first check is valid, and the overhead of spin_lock() can be reduced.
If there is any misunderstanding, please let me know, thanks.
[2]: The reason might be 1. SB_ACTIVE was removed or 2. mapping_shrinkable() return false when I reproduced the bug.
References
- https://www.suse.com/security/cve/CVE-2024-47679.html
- https://bugzilla.suse.com/1231930
- https://git.kernel.org/stable/c/0eed942bc65de1f93eca7bda51344290f9c573bb
- https://git.kernel.org/stable/c/0f8a5b6d0dafa4f533ac82e98f8b812073a7c9d1
- https://git.kernel.org/stable/c/3721a69403291e2514d13a7c3af50a006ea1153b
- https://git.kernel.org/stable/c/47a68c75052a660e4c37de41e321582ec9496195
- https://git.kernel.org/stable/c/540fb13120c9eab3ef203f90c00c8e69f37449d1
- https://git.kernel.org/stable/c/6c857fb12b9137fee574443385d53914356bbe11
- https://git.kernel.org/stable/c/88b1afbf0f6b221f6c5bb66cc80cd3b38d696687
- https://git.kernel.org/stable/c/489faddb1ae75b0e1a741fe5ca2542a2b5e794a5
- https://git.kernel.org/stable/c/6cc13a80a26e6b48f78c725c01b91987d61563ef