linux-cve-announce - CVE-2022-49257: watch_queue: Fix NULL dereference in error cleanup

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Message-ID: <2025022627-CVE-2022-49257-351f@gregkh>
Date: Wed, 26 Feb 2025 02:57:42 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: CVE-2022-49257: watch_queue: Fix NULL dereference in error cleanup

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

The Linux kernel CVE team has assigned CVE-2022-49257 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 5.8 with commit c73be61cede5882f9605a852414db559c0ebedfd and fixed in 5.10.110 with commit 5ae75b4ed30322b42abaa75ef1b784addfdb7dc9
	Issue introduced in 5.8 with commit c73be61cede5882f9605a852414db559c0ebedfd and fixed in 5.15.33 with commit 695c47cea02b9101e2fc2e7d36d552128592b347
	Issue introduced in 5.8 with commit c73be61cede5882f9605a852414db559c0ebedfd and fixed in 5.16.19 with commit 112a2f9b0a8457794095a0450598f150724ec456
	Issue introduced in 5.8 with commit c73be61cede5882f9605a852414db559c0ebedfd and fixed in 5.17.2 with commit b6f5ad3e45d19f9c4ee3e8a2aff829f28d68591d
	Issue introduced in 5.8 with commit c73be61cede5882f9605a852414db559c0ebedfd and fixed in 5.18 with commit a635415a064e77bcfbf43da413fd9dfe0bbed9cb

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2022-49257
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	kernel/watch_queue.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	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