From d78092e4937de9ce55edcb4ee4c5e3c707be0190 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Fri, 18 Sep 2020 10:36:50 +0200 Subject: fuse: fix page dereference after free After unlock_request() pages from the ap->pages[] array may be put (e.g. by aborting the connection) and the pages can be freed. Prevent use after free by grabbing a reference to the page before calling unlock_request(). The original patch was created by Pradeep P V K. Reported-by: Pradeep P V K Cc: Signed-off-by: Miklos Szeredi --- fs/fuse/dev.c | 28 ++++++++++++++++++---------- 1 file changed, 18 insertions(+), 10 deletions(-) (limited to 'fs/fuse/dev.c') diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c index 02b3c36b3676..5078a6ca7dfc 100644 --- a/fs/fuse/dev.c +++ b/fs/fuse/dev.c @@ -785,15 +785,16 @@ static int fuse_try_move_page(struct fuse_copy_state *cs, struct page **pagep) struct page *newpage; struct pipe_buffer *buf = cs->pipebufs; + get_page(oldpage); err = unlock_request(cs->req); if (err) - return err; + goto out_put_old; fuse_copy_finish(cs); err = pipe_buf_confirm(cs->pipe, buf); if (err) - return err; + goto out_put_old; BUG_ON(!cs->nr_segs); cs->currbuf = buf; @@ -833,7 +834,7 @@ static int fuse_try_move_page(struct fuse_copy_state *cs, struct page **pagep) err = replace_page_cache_page(oldpage, newpage, GFP_KERNEL); if (err) { unlock_page(newpage); - return err; + goto out_put_old; } get_page(newpage); @@ -852,14 +853,19 @@ static int fuse_try_move_page(struct fuse_copy_state *cs, struct page **pagep) if (err) { unlock_page(newpage); put_page(newpage); - return err; + goto out_put_old; } unlock_page(oldpage); + /* Drop ref for ap->pages[] array */ put_page(oldpage); cs->len = 0; - return 0; + err = 0; +out_put_old: + /* Drop ref obtained in this function */ + put_page(oldpage); + return err; out_fallback_unlock: unlock_page(newpage); @@ -868,10 +874,10 @@ out_fallback: cs->offset = buf->offset; err = lock_request(cs->req); - if (err) - return err; + if (!err) + err = 1; - return 1; + goto out_put_old; } static int fuse_ref_page(struct fuse_copy_state *cs, struct page *page, @@ -883,14 +889,16 @@ static int fuse_ref_page(struct fuse_copy_state *cs, struct page *page, if (cs->nr_segs >= cs->pipe->max_usage) return -EIO; + get_page(page); err = unlock_request(cs->req); - if (err) + if (err) { + put_page(page); return err; + } fuse_copy_finish(cs); buf = cs->pipebufs; - get_page(page); buf->page = page; buf->offset = offset; buf->len = count; -- cgit v1.2.3