On Mon, Nov 15, 2021 at 7:04 PM Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: > > From: Miklos Szeredi <mszeredi@xxxxxxxxxx> > > 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@xxxxxxxxxx> > Link: https://lore.kernel.org/r/CAAmZXrsGg2xsP1CK+cbuEMumtrqdvD-NKnWzhNcvn71RV3c1yw@xxxxxxxxxxxxxx/ > Fixes: dd3bb14f44a6 ("fuse: support splice() writing to fuse device") > Cc: <stable@xxxxxxxxxxxxxxx> # v2.6.35 > Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx> > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> It appears this patch causes a rather serious regression in flatpacks using portals to access files. Reverting this patch restores expected behavior. I have asked users in the Fedora bug to test with 5.16-rc2 to see if we are just missing a dependent patch in stable, or if this is broken there as well, but no response yet.: https://bugzilla.redhat.com/show_bug.cgi?id=2025285 https://github.com/flatpak/flatpak/issues/4595 Justin Justin
