On Tue, Nov 23, 2021 at 1:22 PM Miklos Szeredi <mszeredi@xxxxxxxxxx> wrote: > > On Tue, Nov 23, 2021 at 7:29 PM Justin Forbes <jmforbes@xxxxxxxxxxx> wrote: > > > > 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 > > Hi, > > Thanks for the report. Can someone with the reproducer try the attached patch? > > I think the race there is unlikely but possible. > Thanks, did a scratch build for that and dropped it in the bug. Only one user has reported back, but the report was that it did not fix the issue. I have also gotten confirmation now that the issue is occuring with 5.16-rc2. Thanks, Justin
