932c29a10d
Prior to commit 4149be7bda7e, sys_flock() would allocate the file_lock struct it was going to use to pass parameters, call ->flock() and then call locks_free_lock() to get rid of it - which had the side effect of calling locks_release_private() and thus ->fl_release_private(). With commit 4149be7bda7e, however, this is no longer the case: the struct is now allocated on the stack, and locks_free_lock() is no longer called - and thus any remaining private data doesn't get cleaned up either. This causes afs flock to cause oops. Kasan catches this as a UAF by the list_del_init() in afs_fl_release_private() for the file_lock record produced by afs_fl_copy_lock() as the original record didn't get delisted. It can be reproduced using the generic/504 xfstest. Fix this by reinstating the locks_release_private() call in sys_flock(). I'm not sure if this would affect any other filesystems. If not, then the release could be done in afs_flock() instead. Changes ======= ver #2) - Don't need to call ->fl_release_private() after calling the security hook, only after calling ->flock(). Fixes: 4149be7bda7e ("fs/lock: Don't allocate file_lock in flock_make_lock().") cc: Chuck Lever <chuck.lever@oracle.com> cc: Jeff Layton <jlayton@kernel.org> cc: Marc Dionne <marc.dionne@auristor.com> cc: linux-afs@lists.infradead.org cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/166075758809.3532462.13307935588777587536.stgit@warthog.procyon.org.uk/ # v1 Acked-by: Kuniyuki Iwashima <kuniyu@amazon.com> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Jeff Layton <jlayton@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.