CVE-2024-39463: Linux Kernel Plan 9 File System Race Condition Local Privilege Escalation Vulnerability
First published: Tue Jun 25 2024(Updated: )
In the Linux kernel, the following vulnerability has been resolved: 9p: add missing locking around taking dentry fid list Fix a use-after-free on dentry's d_fsdata fid list when a thread looks up a fid through dentry while another thread unlinks it: UAF thread: refcount_t: addition on 0; use-after-free. p9_fid_get linux/./include/net/9p/client.h:262 v9fs_fid_find+0x236/0x280 linux/fs/9p/fid.c:129 v9fs_fid_lookup_with_uid linux/fs/9p/fid.c:181 v9fs_fid_lookup+0xbf/0xc20 linux/fs/9p/fid.c:314 v9fs_vfs_getattr_dotl+0xf9/0x360 linux/fs/9p/vfs_inode_dotl.c:400 vfs_statx+0xdd/0x4d0 linux/fs/stat.c:248 Freed by: p9_fid_destroy (inlined) p9_client_clunk+0xb0/0xe0 linux/net/9p/client.c:1456 p9_fid_put linux/./include/net/9p/client.h:278 v9fs_dentry_release+0xb5/0x140 linux/fs/9p/vfs_dentry.c:55 v9fs_remove+0x38f/0x620 linux/fs/9p/vfs_inode.c:518 vfs_unlink+0x29a/0x810 linux/fs/namei.c:4335 The problem is that d_fsdata was not accessed under d_lock, because d_release() normally is only called once the dentry is otherwise no longer accessible but since we also call it explicitly in v9fs_remove that lock is required: move the hlist out of the dentry under lock then unref its fids once they are no longer accessible.
Credit: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 416baaa9-dc9f-4396-8d5f-8c081fb06d67
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Red Hat Kernel-devel | ||
| Linux Kernel | >=5.11<6.1.94 | |
| Linux Kernel | >=6.2<6.6.34 | |
| Linux Kernel | >=6.7<6.9.5 | |
| Linux Kernel | =6.10-rc1 | |
| debian/linux | 5.10.223-1 5.10.234-1 6.1.123-1 6.1.128-1 6.12.12-1 6.12.17-1 |
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Reference Links
- https://lore.kernel.org/linux-cve-announce/2024062513-CVE-2024-39463-42c8@gregkh/T/
- https://www.zerodayinitiative.com/advisories/ZDI-24-1194/
- https://git.kernel.org/stable/c/c898afdc15645efb555acb6d85b484eb40a45409
- https://git.kernel.org/stable/c/cb299cdba09f46f090b843d78ba26b667d50a456
- https://git.kernel.org/stable/c/f0c5c944c6d8614c19e6e9a97fd2011dcd30e8f5
- https://git.kernel.org/stable/c/fe17ebf22feb4ad7094d597526d558a49aac92b4
- https://git.kernel.org/linus/c898afdc15645efb555acb6d85b484eb40a45409
- https://security-tracker.debian.org/tracker/CVE-2024-39463
- https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-39463
- https://nvd.nist.gov/vuln/detail/CVE-2024-39463
- https://launchpad.net/bugs/cve/CVE-2024-39463
- https://ubuntu.com/security/CVE-2024-39463
- https://git.kernel.org/stable/c/3bb6763a8319170c2d41c4232c8e7e4c37dcacfb
Frequently Asked Questions
What is the severity of CVE-2024-39463?
CVE-2024-39463 has a moderate severity level, as it involves a use-after-free vulnerability in the Linux kernel.
How do I fix CVE-2024-39463?
To fix CVE-2024-39463, update your Linux kernel to a version that includes the patches for this vulnerability, specifically versions such as 5.10.223-1 or 6.12.12-1.
Which Linux kernel versions are affected by CVE-2024-39463?
CVE-2024-39463 affects Linux kernel versions from 5.11 to 6.1.94, from 6.2 to 6.6.34, and from 6.7 to 6.9.5, along with version 6.10-rc1.
Is CVE-2024-39463 exploitable?
Yes, CVE-2024-39463 is potentially exploitable in environments where a use-after-free condition can be exploited by unprivileged users.
What systems are most at risk from CVE-2024-39463?
Systems running vulnerable versions of the Linux kernel without the latest patches are at the highest risk for CVE-2024-39463.
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