On Wed, Nov 24, 2021 at 1:04 PM Greg Kroah-Hartman gregkh@linuxfoundation.org wrote:
From: Miklos Szeredi mszeredi@redhat.com
commit 712a951025c0667ff00b25afc360f74e639dfabe upstream.
It is possible to trigger a crash by splicing anon pipe bufs to the fuse device.
The reason for this is that anon_pipe_buf_release() will reuse buf->page if the refcount is 1, but that page might have already been stolen and its flags modified (e.g. PG_lru added).
This happens in the unlikely case of fuse_dev_splice_write() getting around to calling pipe_buf_release() after a page has been stolen, added to the page cache and removed from the page cache.
Fix by calling pipe_buf_release() right after the page was inserted into the page cache. In this case the page has an elevated refcount so any release function will know that the page isn't reusable.
Reported-by: Frank Dinoff fdinoff@google.com Link: https://lore.kernel.org/r/CAAmZXrsGg2xsP1CK+cbuEMumtrqdvD-NKnWzhNcvn71RV3c1y... Fixes: dd3bb14f44a6 ("fuse: support splice() writing to fuse device") Cc: stable@vger.kernel.org # v2.6.35 Signed-off-by: Miklos Szeredi mszeredi@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
Hi Greg,
This patch turned out to have a bug, so stable releases that didn't yet have it released might be better off backing it out for now and releasing only together with the fix to avoid regressions.
Thanks, Miklos