CVE-2024-42271

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.