bcachefs: Add extra padding in bkey_make_mut_noupdate()

This fixes a kasan splat in propagate_key_to_snapshot_leaves() -
varint_decode_fast() does reads (that it never uses) up to 7 bytes past
the end of the integer.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/fs/bcachefs/btree_update.h b/fs/bcachefs/btree_update.h
index 60393e98084d7952771e0d02ba9246183977e233..6a454f2fa00534082a8013a3c7db321cabcbf603 100644 (file)
--- a/fs/bcachefs/btree_update.h
+++ b/fs/bcachefs/btree_update.h
@@ -220,7 +220,8 @@ static inline struct bkey_i *__bch2_bkey_make_mut_noupdate(struct btree_trans *t
        if (type && k.k->type != type)
                return ERR_PTR(-ENOENT);
 
-       mut = bch2_trans_kmalloc_nomemzero(trans, bytes);
+       /* extra padding for varint_decode_fast... */
+       mut = bch2_trans_kmalloc_nomemzero(trans, bytes + 8);
        if (!IS_ERR(mut)) {
                bkey_reassemble(mut, k);