CVE-2022-49256 in Linux
Summary
by MITRE • 02/26/2025
In the Linux kernel, the following vulnerability has been resolved:
watch_queue: Actually free the watch
free_watch() does everything barring actually freeing the watch object. Fix this by adding the missing kfree.
kmemleak produces a report something like the following. Note that as an address can be seen in the first word, the watch would appear to have gone through call_rcu().
BUG: memory leak unreferenced object 0xffff88810ce4a200 (size 96): comm "syz-executor352", pid 3605, jiffies 4294947473 (age 13.720s) hex dump (first 32 bytes): e0 82 48 0d 81 88 ff ff 00 00 00 00 00 00 00 00 ..H............. 80 a2 e4 0c 81 88 ff ff 00 00 00 00 00 00 00 00 ................ backtrace: [] kmalloc include/linux/slab.h:581 [inline]
[] kzalloc include/linux/slab.h:714 [inline]
[] keyctl_watch_key+0xec/0x2e0 security/keys/keyctl.c:1800
[] __do_sys_keyctl+0x3c4/0x490 security/keys/keyctl.c:2016
[] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
[] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
[] entry_SYSCALL_64_after_hwframe+0x44/0xae
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Analysis
by VulDB Data Team • 02/16/2026
The vulnerability described in CVE-2022-49256 represents a memory leak within the Linux kernel's key management subsystem, specifically affecting the watch_queue functionality. This issue occurs in the keyctl_watch_key function where the free_watch() routine is responsible for cleaning up watch objects but fails to actually release the memory allocated for these objects. The flaw manifests as a kmemleak report indicating that watch objects remain unreferenced despite the completion of their lifecycle, creating persistent memory consumption that could degrade system performance over time.
The technical implementation of this vulnerability stems from an incomplete cleanup routine within the kernel's security key management framework. When a watch object is created through the keyctl_watch_key system call, the corresponding free_watch() function performs all necessary cleanup operations except for the final memory deallocation step. This oversight results in memory that should be freed remaining allocated and tracked by the kernel's memory management subsystem. The memory leak is particularly significant because watch objects are created and destroyed frequently in security-critical operations, making this a persistent resource drain that could eventually impact system stability and performance.
The operational impact of CVE-2022-49256 extends beyond simple memory consumption issues to potentially affect system reliability and resource availability. While individual memory leaks may appear minor, in high-frequency operations involving key management and security monitoring, these leaks accumulate and can lead to memory exhaustion conditions. The vulnerability affects systems running Linux kernel versions where the watch_queue functionality is active, particularly those implementing security key management features. Attackers could potentially exploit this memory leak to cause denial of service conditions by exhausting system memory through repeated creation and improper cleanup of watch objects.
Mitigation strategies for this vulnerability involve applying the kernel patch that corrects the free_watch() function to include the missing kfree() call, ensuring proper memory deallocation. System administrators should prioritize updating their kernel installations to versions containing the fix, as this addresses the root cause of the memory leak. Additionally, monitoring systems should be implemented to detect unusual memory consumption patterns that might indicate the presence of this vulnerability. The fix aligns with security best practices for memory management and follows the principle of least privilege by ensuring proper resource cleanup. This vulnerability demonstrates the importance of thorough code review processes and automated memory leak detection tools in kernel development, as highlighted by CWE-401 which addresses improper release of memory resources. The issue also relates to ATT&CK technique T1490 which involves resource exhaustion through memory leaks, making it a significant concern for system administrators monitoring security and performance metrics.