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fuse: re-lock request before replacing page cache folio

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commit a078484921052d0badd827fcc2770b5cfc1d4120 upstream.

fuse_try_move_folio() unlocks the request on entry but does not
re-lock it on the success path. This means fuse_chan_abort() can end the
request and free the fuse_io_args (eg fuse_readpages_end()) while the
subsequent copy chain logic after fuse_try_move_folio() accesses the
fuse_io_args, leading to use-after-free issues.

Fix this by calling lock_request() before replace_page_cache_folio().
This ensures the request is locked on the success path which will
prevent the fuse_io_args from being freed while the later copying logic
runs, and also ensures that the ap->folios[i]->mapping is never null
since ap->folios[i] will always point to the newfolio after
replace_page_cache_folio().

Fixes: ce534fb052 ("fuse: allow splice to move pages")
Cc: stable@vger.kernel.org
Reported-by: Lei Lu <llfamsec@gmail.com>
Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Joanne Koong 2026-05-18 22:28:06 -07:00 • committed by Greg Kroah-Hartman
commit e28db6ac47
1 changed files with 5 additions and 14 deletions
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19
fs/fuse/dev.c
View file

@ -1037,6 +1037,10 @@ static int fuse_try_move_folio(struct fuse_copy_state *cs, struct folio **foliop
if (WARN_ON(folio_test_mlocked(oldfolio)))
goto out_fallback_unlock;
err = lock_request(cs->req);
if (err)
goto out_fallback_unlock;
replace_page_cache_folio(oldfolio, newfolio);
folio_get(newfolio);
@ -1050,20 +1054,7 @@ static int fuse_try_move_folio(struct fuse_copy_state *cs, struct folio **foliop
*/
pipe_buf_release(cs->pipe, buf);
err = 0;
spin_lock(&cs->req->waitq.lock);
if (test_bit(FR_ABORTED, &cs->req->flags))
err = -ENOENT;
else
*foliop = newfolio;
spin_unlock(&cs->req->waitq.lock);
if (err) {
folio_unlock(newfolio);
folio_put(newfolio);
goto out_put_old;
}
*foliop = newfolio;
folio_unlock(oldfolio);
/* Drop ref for ap->pages[] array */
folio_put(oldfolio);