| From 3527a018c00e5dbada2f9d7ed5576437b6dd5cfb Mon Sep 17 00:00:00 2001 |
| From: Filipe Manana <fdmanana@suse.com> |
| Date: Sat, 13 Oct 2018 00:37:25 +0100 |
| Subject: Btrfs: fix null pointer dereference on compressed write path error |
| |
| From: Filipe Manana <fdmanana@suse.com> |
| |
| 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 <bo.liu@linux.alibaba.com> |
| Signed-off-by: Filipe Manana <fdmanana@suse.com> |
| Reviewed-by: David Sterba <dsterba@suse.com> |
| Signed-off-by: David Sterba <dsterba@suse.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| fs/btrfs/inode.c | 1 + |
| 1 file changed, 1 insertion(+) |
| |
| --- a/fs/btrfs/inode.c |
| +++ b/fs/btrfs/inode.c |
| @@ -489,6 +489,7 @@ again: |
| pages = kcalloc(nr_pages, sizeof(struct page *), GFP_NOFS); |
| if (!pages) { |
| /* just bail out to the uncompressed code */ |
| + nr_pages = 0; |
| goto cont; |
| } |
| |