CVE-2024-47741 json
btrfs: fix race setting file private on concurrent lseek using same fd
published 2024-10-21 2 y ago modified 2026-08-05 3 mo ago also EUVD-2024-42658
- cvss
- 7.8
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.2%
- EPSS 0.2% chance of exploitation in 30 days, percentile 5%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- Linux Linux 6.6.54, 6.10.13, 6.11.2, 6.12
- linux Debian 14, Debian 13 6.11.2-1
debian advisories DEBIAN-CVE-2024-47741
- linux Ubuntu 24.04 LTS 6.8.0-54.56
- linux-aws Ubuntu 24.04 LTS 6.8.0-1023.25
- linux-gcp Ubuntu 24.04 LTS 6.8.0-1024.26
- linux-gke Ubuntu 24.04 LTS 6.8.0-1019.23
- linux-ibm Ubuntu 24.04 LTS 6.8.0-1022.22
- linux-azure Ubuntu 24.04 LTS 6.8.0-1025.30
- linux-gkeop Ubuntu 24.04 LTS 6.8.0-1006.8
- linux-raspi Ubuntu 24.04 LTS 6.8.0-1019.23
ubuntu advisories UBUNTU-CVE-2024-47741
Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0
- kernel-source Linux Micro 6.1, Linux Micro 6.0 6.4.0-24.1
- kernel-default Linux Micro 6.1, Linux Micro 6.0 6.4.0-24.1
- kernel-kvmsmall Linux Micro 6.1, Linux Micro 6.0 6.4.0-24.1
- kernel-default-base Linux Micro 6.1, Linux Micro 6.0 6.4.0-24.1.21.4
- kernel-livepatch-MICRO-6-0_Update_4 Linux Micro 6.1, Linux Micro 6.0 1-1.2
- kernel-rt Linux Micro 6.1, Linux Micro 6.0 6.4.0-22.1
- kernel-source-rt Linux Micro 6.1, Linux Micro 6.0 6.4.0-22.1
- kernel-livepatch-MICRO-6-0-RT_Update_4 Linux Micro 6.1, Linux Micro 6.0 1-1.1
suse advisories SUSE-SU-2025:20164-1SUSE-SU-2025:20247-1SUSE-SU-2025:20163-1SUSE-SU-2025:20246-1SUSE-SU-2024:4387-1SUSE-SU-2024:4318-1
- kernel-source-longterm openSUSE Tumbleweed 6.12.11-1.1
- kernel-source openSUSE Tumbleweed 6.11.8-1.1
opensuse advisories openSUSE-SU-2025:14705-1openSUSE-SU-2024:14500-1
Vendor advisories
What the vendors themselves say about their products: affected, fixed or not affected, and what to do.
red hat product security vex CVE-2024-47741 updated cvss 7.0
kernel: btrfs: fix race setting file private on concurrent lseek using same fd
-
Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 moreaffected: workaround, no fix planned “Out of support scope”
-
Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 morenot affected: vulnerable code not present
Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 2 y ago
Exploit prediction
0.17% chance of exploitation in the next 30 days, higher than 5% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 7.8 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
| NVD | 3.1 | 7.0 | CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H |
Affected products
- Linux Linux
Classification
- Weakness
-
- CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization
- Technology feeds
References
Sources
- CVE List CVE-2024-47741
- NVD CVE-2024-47741
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