From: Filipe Manana Date: Fri, 12 Oct 2018 23:37:25 +0000 (+0100) Subject: Btrfs: fix null pointer dereference on compressed write path error X-Git-Tag: v4.14.81~13 X-Git-Url: http://git.hungrycats.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=bdda31751a2074cbfcf64f52b59b165c06204ae5;p=linux Btrfs: fix null pointer dereference on compressed write path error commit 3527a018c00e5dbada2f9d7ed5576437b6dd5cfb upstream. At inode.c:compress_file_range(), under the "free_pages_out" label, we can end up dereferencing the "pages" pointer when it has a NULL value. This case happens when "start" has a value of 0 and we fail to allocate memory for the "pages" pointer. When that happens we jump to the "cont" label and then enter the "if (start == 0)" branch where we immediately call the cow_file_range_inline() function. If that function returns 0 (success creating an inline extent) or an error (like -ENOMEM for example) we jump to the "free_pages_out" label and then access "pages[i]" leading to a NULL pointer dereference, since "nr_pages" has a value greater than zero at that point. Fix this by setting "nr_pages" to 0 when we fail to allocate memory for the "pages" pointer. Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=201119 Fixes: 771ed689d2cd ("Btrfs: Optimize compressed writeback and reads") CC: stable@vger.kernel.org # 4.4+ Reviewed-by: Liu Bo Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman --- diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index e8bfafa25a71..c24badcafcc0 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -524,6 +524,7 @@ again: pages = kcalloc(nr_pages, sizeof(struct page *), GFP_NOFS); if (!pages) { /* just bail out to the uncompressed code */ + nr_pages = 0; goto cont; }