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 bug[1] 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.
[1]: https://lore.kernel.org/linux-btrfs/000000000000eabe1d0619c48986@google.com/
[2]: The reason might be 1. SB_ACTIVE was removed or 2. mapping_shrinkable()
return false when I reproduced the bug.
References
Configurations
Configuration 1 (hide)
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History
08 Nov 2024, 16:15
| Type | Values Removed | Values Added |
|---|---|---|
| References |
|
23 Oct 2024, 14:49
| Type | Values Removed | Values Added |
|---|---|---|
| CWE | CWE-362 | |
| First Time |
Linux linux Kernel
Linux |
|
| CVSS |
v2 : v3 : |
v2 : unknown
v3 : 4.7 |
| CPE | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| References | () https://git.kernel.org/stable/c/0eed942bc65de1f93eca7bda51344290f9c573bb - Patch | |
| References | () https://git.kernel.org/stable/c/0f8a5b6d0dafa4f533ac82e98f8b812073a7c9d1 - Patch | |
| References | () https://git.kernel.org/stable/c/3721a69403291e2514d13a7c3af50a006ea1153b - Patch | |
| References | () https://git.kernel.org/stable/c/47a68c75052a660e4c37de41e321582ec9496195 - Patch | |
| References | () https://git.kernel.org/stable/c/540fb13120c9eab3ef203f90c00c8e69f37449d1 - Patch | |
| References | () https://git.kernel.org/stable/c/6c857fb12b9137fee574443385d53914356bbe11 - Patch | |
| References | () https://git.kernel.org/stable/c/88b1afbf0f6b221f6c5bb66cc80cd3b38d696687 - Patch | |
| Summary |
|
21 Oct 2024, 12:15
| Type | Values Removed | Values Added |
|---|---|---|
| New CVE |
Information
Published : 2024-10-21 12:15
Updated : 2024-11-08 16:15
NVD link : CVE-2024-47679
Mitre link : CVE-2024-47679
CVE.ORG link : CVE-2024-47679
JSON object : View
Products Affected
linux
- linux_kernel
CWE
CWE-362
Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')