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Wed, 4 Nov 2026 14:23:57 -0500 (EST) Date: Wed, 4 Nov 2026 11:24:15 -0800 From: Boris Burkov To: Siddharth Mishra Cc: dsterba@suse.com, wqu@suse.com, josef@toxicpanda.com, fdmanana@suse.com, mason@kernel.org, linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/5] btrfs: tree-checker: reject inline refs not matching the extent type Message-ID: <20261104192415.GD3301639@zen.localdomain> References: <20261104102323.4090290-1-smish149@asu.edu> <20261104102323.4090290-3-smish149@asu.edu> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261104102323.4090290-3-smish149@asu.edu> On Wed, Nov 04, 2026 at 03:23:20AM -0700, Siddharth Mishra wrote: > [BACKGROUND] > An extent item is either for a tree block or for data, and each kind > only gets its own inline ref types: > > TREE_BLOCK: TREE_BLOCK_REF, SHARED_BLOCK_REF > DATA: EXTENT_OWNER_REF, EXTENT_DATA_REF, SHARED_DATA_REF > > Readers rely on this. btrfs_get_extent_owner_root() only looks for an > owner ref on data extents, and btrfs_get_extent_inline_ref_type() warns > when a caller that expects a tree block ref or a data ref gets the > other kind. > > [CAUSE] > check_extent_item() verifies each inline ref on its own, but never > checks that its type matches the TREE_BLOCK or DATA flag of the extent > item. So a data ref or an owner ref on a tree block, or a tree block > ref on a data extent, passes the tree-checker. For example this tree > block has an owner ref instead of its tree block ref: > > item 9 key (30478336 METADATA_ITEM 0) itemoff 3636 itemsize 33 > refs 1 gen 13 flags TREE_BLOCK > tree block skinny level 0 > (172 0x5) extent owner root 5 > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > I assume this was crafted manually, not via btrfs operations with squotas enabled, right? > The leaf is accepted. When the tree block is freed later, > lookup_inline_extent_backref() skips the owner ref, finds no tree block > ref, and the transaction aborts: > > WARNING: fs/btrfs/extent-tree.c:3418 at __btrfs_free_extent > BTRFS error (device vda state A): Transaction 14 aborted (-EUCLEAN) > BTRFS info (device vda state EA): forced readonly This part is not that interesting, kinda garbage in garbage out > > [ENHANCEMENT] > Reject an inline ref whose type does not match the extent flags with > -EUCLEAN, so the leaf is refused when it is read: > > BTRFS critical (device vda): corrupt leaf: block=30441472 slot=9 > extent bytenr=30478336 len=4096 inline ref type 172 does not match > extent flags 0x2 but of course nice to catch more corrupt leaves > > Signed-off-by: Siddharth Mishra > --- > fs/btrfs/tree-checker.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c > index f021ac14b..db446c8af 100644 > --- a/fs/btrfs/tree-checker.c > +++ b/fs/btrfs/tree-checker.c > @@ -1790,6 +1790,14 @@ static int check_extent_item(struct extent_buffer *leaf, > inline_type); > return -EUCLEAN; > } Logic itself is maybe too clever but at least quite compact. LGTM Reviewed-by: Boris Burkov > + if (unlikely(is_tree_block != > + (inline_type == BTRFS_TREE_BLOCK_REF_KEY || > + inline_type == BTRFS_SHARED_BLOCK_REF_KEY))) { > + extent_err(leaf, slot, > + "inline ref type %u does not match extent flags 0x%llx", > + inline_type, flags); > + return -EUCLEAN; > + } > if (unlikely(inline_type < last_type)) { > extent_err(leaf, slot, > "inline ref out-of-order: has type %u, prev type %u", > -- > 2.54.0 >