CVE-2026-74646: misc: fastrpc: take fl->lock when moving mmaps on interrupted invoke

From: Greg Kroah-Hartman <[email protected]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

misc: fastrpc: take fl->lock when moving mmaps on interrupted invoke

When an invoke is interrupted by a signal,
wait_for_completion_interruptible() returns -ERESTARTSYS and
fastrpc_internal_invoke() moves every buffer from fl->mmaps onto
cctx->invoke_interrupted_mmaps. This list_del()/list_add_tail() walk
runs without holding fl->lock, the lock that serialises fl->mmaps in
fastrpc_req_mmap() and fastrpc_req_munmap() everywhere else.

Take fl->lock around the move, matching every other fl->mmaps accessor.

The Linux kernel CVE team has assigned CVE-2026-74646 to this issue.


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

	Issue introduced in 6.2 with commit 76e8e4ace1ed2c97dba3b1370e0e105e07c572bc and fixed in 6.6.152 with commit 3f265e405e5ef85030c3777262e18bb556bc8724
	Issue introduced in 6.2 with commit 76e8e4ace1ed2c97dba3b1370e0e105e07c572bc and fixed in 6.12.104 with commit a902fe1f80f58a2335b6be1131866f827ec44d1a
	Issue introduced in 6.2 with commit 76e8e4ace1ed2c97dba3b1370e0e105e07c572bc and fixed in 6.18.45 with commit af6345159abcbaa550518f31990d2a9558c2d369
	Issue introduced in 6.2 with commit 76e8e4ace1ed2c97dba3b1370e0e105e07c572bc and fixed in 7.1.9 with commit efd02f8d1a7449f15809bc18d3cd41aafea75d7e
	Issue introduced in 6.2 with commit 76e8e4ace1ed2c97dba3b1370e0e105e07c572bc and fixed in 7.2 with commit b85a0e91d7d6cd06a53c881a46f749cfcef416a2

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-2026-74646
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:
	drivers/misc/fastrpc.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/3f265e405e5ef85030c3777262e18bb556bc8724
	https://git.kernel.org/stable/c/a902fe1f80f58a2335b6be1131866f827ec44d1a
	https://git.kernel.org/stable/c/af6345159abcbaa550518f31990d2a9558c2d369
	https://git.kernel.org/stable/c/efd02f8d1a7449f15809bc18d3cd41aafea75d7e
	https://git.kernel.org/stable/c/b85a0e91d7d6cd06a53c881a46f749cfcef416a2