3.16.63-rc1 review patch. If anyone has any objections, please let me know.
------------------
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") 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: Ben Hutchings ben@decadent.org.uk --- fs/btrfs/inode.c | 1 + 1 file changed, 1 insertion(+)
--- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -452,6 +452,7 @@ again: pages = kzalloc(sizeof(struct page *) * nr_pages, GFP_NOFS); if (!pages) { /* just bail out to the uncompressed code */ + nr_pages = 0; goto cont; }