bcachefs: Array bounds fixes

It's no longer legal to use a zero size array as a flexible array
member - this causes UBSAN to complain.

This patch switches our zero size arrays to normal flexible array
members when possible, and inserts casts in other places (e.g. where we
use the zero size array as a marker partway through an array).

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

1 files changed, 7 insertions, 6 deletions

diff --git a/fs/bcachefs/bset.c b/fs/bcachefs/bset.c
index bcdf28f39b9c..685792137d2a 100644
--- a/fs/bcachefs/bset.c
+++ b/fs/bcachefs/bset.c
@@ -232,7 +232,7 @@ void bch2_verify_insert_pos(struct btree *b, struct bkey_packed *where,
 {
 	struct bset_tree *t = bch2_bkey_to_bset(b, where);
 	struct bkey_packed *prev = bch2_bkey_prev_all(b, t, where);
-	struct bkey_packed *next = (void *) (where->_data + clobber_u64s);
+	struct bkey_packed *next = (void *) ((u64 *) where->_data + clobber_u64s);
 	struct printbuf buf1 = PRINTBUF;
 	struct printbuf buf2 = PRINTBUF;
 #if 0
@@ -300,7 +300,8 @@ static unsigned bkey_float_byte_offset(unsigned idx)
 }
 
 struct ro_aux_tree {
-	struct bkey_float	f[0];
+	u8			nothing[0];
+	struct bkey_float	f[];
 };
 
 struct rw_aux_tree {
@@ -476,7 +477,7 @@ static struct bkey_packed *tree_to_prev_bkey(const struct btree *b,
 {
 	unsigned prev_u64s = ro_aux_tree_prev(b, t)[j];
 
-	return (void *) (tree_to_bkey(b, t, j)->_data - prev_u64s);
+	return (void *) ((u64 *) tree_to_bkey(b, t, j)->_data - prev_u64s);
 }
 
 static struct rw_aux_tree *rw_aux_tree(const struct btree *b,
@@ -1010,8 +1011,8 @@ void bch2_bset_insert(struct btree *b,
 		btree_keys_account_key_add(&b->nr, t - b->set, src);
 
 	if (src->u64s != clobber_u64s) {
-		u64 *src_p = where->_data + clobber_u64s;
-		u64 *dst_p = where->_data + src->u64s;
+		u64 *src_p = (u64 *) where->_data + clobber_u64s;
+		u64 *dst_p = (u64 *) where->_data + src->u64s;
 
 		EBUG_ON((int) le16_to_cpu(bset(b, t)->u64s) <
 			(int) clobber_u64s - src->u64s);
@@ -1037,7 +1038,7 @@ void bch2_bset_delete(struct btree *b,
 		      unsigned clobber_u64s)
 {
 	struct bset_tree *t = bset_tree_last(b);
-	u64 *src_p = where->_data + clobber_u64s;
+	u64 *src_p = (u64 *) where->_data + clobber_u64s;
 	u64 *dst_p = where->_data;
 
 	bch2_bset_verify_rw_aux_tree(b, t);