Red Hat: CVE-2024-42271: kernel: net/iucv: fix use after free in iucv_sock_close() (Multiple Advisories)

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] ([] 0x1e87f03880)
[452744.123966] [] iucv_path_sever+0x96/0x138
[452744.124330] [] iucv_sever_path+0xc2/0xd0 [af_iucv]
[452744.124336] [] iucv_sock_close+0xa6/0x310 [af_iucv]
[452744.124341] [] iucv_sock_release+0x3c/0xd0 [af_iucv]
[452744.124345] [] __sock_release+0x5e/0xe8
[452744.124815] [] sock_close+0x34/0x48
[452744.124820] [] __fput+0xba/0x268
[452744.124826] [] task_work_run+0xbc/0xf0
[452744.124832] [] do_notify_resume+0x88/0x90
[452744.124841] [] system_call+0xe2/0x2c8
[452744.125319] Last Breaking-Event-Address:
[452744.125321] [] 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.