Linux: Concurrent Execution using Shared Resource with Improper Synchronization
CVE-2024-47741 is a high-severity concurrent execution using shared resource with improper synchronization vulnerability in Linux, with a CVSS 3.1 base score of 7.0 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions f56a6d9c267ec7fa558ede7755551c047b1034cd, a412ca489ac27b9d0e603499315b7139c948130d, 33d1310d4496e904123dab9c28b2d8d2c1800f97 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.17% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to f56a6d9c267ec7fa558ede7755551c047b1034cd or a412ca489ac27b9d0e603499315b7139c948130d or 33d1310d4496e904123dab9c28b2d8d2c1800f97 or 7ee85f5515e86a4e2a2f51969795920733912bad, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.6.54 or 6.10.13 or 6.11.2, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 3c32c7212f1639471ec0197ff1179b8ef2e0f3d3 up to, but not including, f56a6d9c267ec7fa558ede7755551c047b1034cd; 3c32c7212f1639471ec0197ff1179b8ef2e0f3d3 up to, but not including, a412ca489ac27b9d0e603499315b7139c948130d; 3c32c7212f1639471ec0197ff1179b8ef2e0f3d3 up to, but not including, 33d1310d4496e904123dab9c28b2d8d2c1800f97; 3c32c7212f1639471ec0197ff1179b8ef2e0f3d3 up to, but not including, 7ee85f5515e86a4e2a2f51969795920733912bad; 6.2 | f56a6d9c267ec7fa558ede7755551c047b1034cd, a412ca489ac27b9d0e603499315b7139c948130d, 33d1310d4496e904123dab9c28b2d8d2c1800f97, 7ee85f5515e86a4e2a2f51969795920733912bad |
| Linux | Linux Kernel | 6.2 up to, but not including, 6.6.54; 6.7 up to, but not including, 6.10.13; 6.11 up to, but not including, 6.11.2 | 6.6.54, 6.10.13, 6.11.2 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- HighSuccess depends on conditions outside the attacker's control.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.8 | High | CNA |
| CVSS 3.1 | 7.0 | High | NVD |
Official description
In the Linux kernel, the following vulnerability has been resolved: btrfs: fix race setting file private on concurrent lseek using same fd When doing concurrent lseek(2) system calls against the same file descriptor, using multiple threads belonging to the same process, we have a short time window where a race happens and can result in a memory leak. The race happens like this: 1) A program opens a file descriptor for a file and then spawns two threads (with the pthreads library for example), lets call them task A and task B; 2) Task A calls lseek with SEEK_DATA or SEEK_HOLE and ends up at file.c:find_desired_extent() while holding a read lock on the inode; 3) At the start of find_desired_extent(), it extracts the file's private_data pointer into a local variable named 'private', which has a value of NULL; 4) Task B also calls lseek with SEEK_DATA or SEEK_HOLE, locks the inode in shared mode and enters file.c:find_desired_extent(), where it also extracts file->private_data into its local variable 'private', which has a NULL value; 5) Because it saw a NULL file private, task A allocates a private structure and assigns to the file structure; 6) Task B also saw a NULL file private so it also allocates its own file private and then assigns it to the same file structure, since both tasks are using the same file descriptor. At this point we leak the private structure allocated by task A. Besides the memory leak, there's also the detail that both tasks end up using the same cached state record in the private structure (struct btrfs_file_private::llseek_cached_state), which can result in a use-after-free problem since one task can free it while the other is still using it (only one task took a reference count on it). Also, sharing the cached state is not a good idea since it could result in incorrect results in the future - right now it should not be a problem because it end ups being used only in extent-io-tree.c:count_range_bits() where we do range validation before using the cached state. Fix this by protecting the private assignment and check of a file while holding the inode's spinlock and keep track of the task that allocated the private, so that it's used only by that task in order to prevent user-after-free issues with the cached state record as well as potentially using it incorrectly in the future.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Concurrent Execution using Shared Resource with Improper Synchronization
The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.
How developers prevent this class of flaw
- In languages that support it, use synchronization primitives. Only wrap these around critical code to minimize the impact on performance.
- Use thread-safe capabilities such as the data access abstraction in Spring.
- Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring. Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Recent Concurrent Execution using Shared Resource with Improper Synchronization vulnerabilities
- 7.0 High severity
- 7.0 High severity
- 8.1 High severity
- 8.2 High severity
- 7.9 High severity
- 7.5 High severity
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