btrfs: exit after state split error at set_extent_bit()

If split_state() returned an error we call extent_io_tree_panic() which
will trigger a BUG() call. However if CONFIG_BUG is disabled, which is an
uncommon and exotic scenario, then we fallthrough and hit a use after free
when calling set_state_bits() since the extent state record which the
local variable 'prealloc' points to was freed by split_state().

So jump to the label 'out' after calling extent_io_tree_panic() and set
the 'prealloc' pointer to NULL since split_state() has already freed it
when it hit an error.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/extent-io-tree.c b/fs/btrfs/extent-io-tree.c
index 29cf3a01294f6f08f1c0fee8e951f4ce176ba5fd..36bdf9df7b4caef82f3d67cef342208afff27a66 100644 (file)
--- a/fs/btrfs/extent-io-tree.c
+++ b/fs/btrfs/extent-io-tree.c
@@ -1250,8 +1250,11 @@ hit_next:
                if (!prealloc)
                        goto search_again;
                ret = split_state(tree, state, prealloc, end + 1);
-               if (ret)
+               if (ret) {
                        extent_io_tree_panic(tree, state, "split", ret);
+                       prealloc = NULL;
+                       goto out;
+               }
 
                set_state_bits(tree, prealloc, bits, changeset);
                cache_state(prealloc, cached_state);