Public bug reported: [Impact]
Currently when the client creates a cifsFileInfo structure for a newly opened file, it allocates a list of byte-range locks with a pointer to the new cfile and attaches this list to the inode's lock list. The latter happens before initializing all other fields, e.g. cfile->tlink. Thus a partially initialized cifsFileInfo structure becomes available to other threads that walk through the inode's lock list. One example of such a thread may be an oplock break worker thread that tries to push all cached byte-range locks. This causes NULL-pointer dereference in smb2_push_mandatory_locks() when accessing cfile->tlink: [598428.945633] BUG: kernel NULL pointer dereference, address: 0000000000000038 ... [598428.945749] Workqueue: cifsoplockd cifs_oplock_break [cifs] [598428.945793] RIP: 0010:smb2_push_mandatory_locks+0xd6/0x5a0 [cifs] ... [598428.945834] Call Trace: [598428.945870] ? cifs_revalidate_mapping+0x45/0x90 [cifs] [598428.945901] cifs_oplock_break+0x13d/0x450 [cifs] [598428.945909] process_one_work+0x1db/0x380 [598428.945914] worker_thread+0x4d/0x400 [598428.945921] kthread+0x104/0x140 [598428.945925] ? process_one_work+0x380/0x380 [598428.945931] ? kthread_park+0x80/0x80 [598428.945937] ret_from_fork+0x35/0x40 [Test Case] TBD. [Fix] Backport commit 6f582b273ec23332074d970a7fb25bef835df71f ("CIFS: Fix NULL-pointer dereference in smb2_push_mandatory_locks") [Regression Potential] Low. The patch is fairly simple and it's tagged for stable kernels. In fact it is already in some of the released upstream stable kernels. ** Affects: linux (Ubuntu) Importance: Undecided Status: Incomplete ** Affects: linux (Ubuntu Xenial) Importance: Undecided Status: Incomplete ** Affects: linux (Ubuntu Bionic) Importance: Undecided Status: Incomplete ** Affects: linux (Ubuntu Disco) Importance: Undecided Status: Incomplete ** Affects: linux (Ubuntu Eoan) Importance: Undecided Status: Incomplete ** Also affects: linux (Ubuntu Focal) Importance: Undecided Status: New ** Also affects: linux (Ubuntu Bionic) Importance: Undecided Status: New ** Also affects: linux (Ubuntu Eoan) Importance: Undecided Status: New ** Also affects: linux (Ubuntu Xenial) Importance: Undecided Status: New ** Also affects: linux (Ubuntu Disco) Importance: Undecided Status: New -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1856949 Title: cifs: kernel NULL pointer dereference, address: 0000000000000038 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1856949/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs