Subject: CVE-2024-42271: net/iucv: fix use after free in iucv_sock_close()

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

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

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

net/iucv: fix use after free in iucv_sock_close()

iucv_sever_path() is called from process context and from bh context.
iucv->path is used as indicator whether somebody else is taking care of
severing the path (or it is already removed / never existed).
This needs to be done with atomic compare and swap, otherwise there is a
small window where iucv_sock_close() will try to work with a path that has
already been severed and freed by iucv_callback_connrej() called by
iucv_tasklet_fn().

Example:
[452744.123844] Call Trace:
[452744.123845] ([<0000001e87f03880>] 0x1e87f03880)
[452744.123966]  [<00000000d593001e>] iucv_path_sever+0x96/0x138
[452744.124330]  [<000003ff801ddbca>] iucv_sever_path+0xc2/0xd0 [af_iucv]
[452744.124336]  [<000003ff801e01b6>] iucv_sock_close+0xa6/0x310 [af_iucv]
[452744.124341]  [<000003ff801e08cc>] iucv_sock_release+0x3c/0xd0 [af_iucv]
[452744.124345]  [<00000000d574794e>] __sock_release+0x5e/0xe8
[452744.124815]  [<00000000d5747a0c>] sock_close+0x34/0x48
[452744.124820]  [<00000000d5421642>] __fput+0xba/0x268
[452744.124826]  [<00000000d51b382c>] task_work_run+0xbc/0xf0
[452744.124832]  [<00000000d5145710>] do_notify_resume+0x88/0x90
[452744.124841]  [<00000000d5978096>] system_call+0xe2/0x2c8
[452744.125319] Last Breaking-Event-Address:
[452744.125321]  [<00000000d5930018>] iucv_path_sever+0x90/0x138
[452744.125324]
[452744.125325] Kernel panic - not syncing: Fatal exception in interrupt

Note that bh_lock_sock() is not serializing the tasklet context against
process context, because the check for sock_owned_by_user() and
corresponding handling is missing.

Ideas for a future clean-up patch:
A) Correct usage of bh_lock_sock() in tasklet context, as described in
Re-enqueue, if needed. This may require adding return values to the
tasklet functions and thus changes to all users of iucv.

B) Change iucv tasklet into worker and use only lock_sock() in af_iucv.

The Linux kernel CVE team has assigned CVE-2024-42271 to this issue.

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

	Issue introduced in 3.4 with commit 7d316b945352 and fixed in 4.19.320 with commit 84f40b46787e
	Issue introduced in 3.4 with commit 7d316b945352 and fixed in 5.4.282 with commit 37652fbef980
	Issue introduced in 3.4 with commit 7d316b945352 and fixed in 5.10.224 with commit c65f72eec60a
	Issue introduced in 3.4 with commit 7d316b945352 and fixed in 5.15.165 with commit ac758e1f663f
	Issue introduced in 3.4 with commit 7d316b945352 and fixed in 6.1.104 with commit 8b424c9e4411
	Issue introduced in 3.4 with commit 7d316b945352 and fixed in 6.6.45 with commit 01437282fd39
	Issue introduced in 3.4 with commit 7d316b945352 and fixed in 6.10.4 with commit 69620522c48c
	Issue introduced in 3.4 with commit 7d316b945352 and fixed in 6.11 with commit f558120cd709

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-2024-42271
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:
	net/iucv/af_iucv.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/84f40b46787ecb67c7ad08a5bb1376141fa10c01
	https://git.kernel.org/stable/c/37652fbef9809411cea55ea5fa1a170e299efcd0
	https://git.kernel.org/stable/c/c65f72eec60a34ace031426e04e9aff8e5f04895
	https://git.kernel.org/stable/c/ac758e1f663fe9bc64f6b47212a2aa18697524f5
	https://git.kernel.org/stable/c/8b424c9e44111c5a76f41c6b741f8d4c4179d876
	https://git.kernel.org/stable/c/01437282fd3904810603f3dc98d2cac6b8b6fc84
	https://git.kernel.org/stable/c/69620522c48ce8215e5eb55ffbab8cafee8f407d
	https://git.kernel.org/stable/c/f558120cd709682b739207b48cf7479fd9568431