bcachefs: bch2_bkey_format_field_overflows()

Fix another shift-by-64 by factoring out a common helper for
bch2_bkey_format_invalid() and bformat_needs_redo() (where it was
already fixed).

Reported-by: syzbot+9833a1d29d4a44361e2c@syzkaller.appspotmail.com
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/bkey.c

@@ -656,20 +656,17 @@ int bch2_bkey_format_invalid(struct bch_fs *c,
 	 * unpacked format:
 	 */
 	for (i = 0; i < f->nr_fields; i++) {
-		if (!c || c->sb.version_min >= bcachefs_metadata_version_snapshot) {
+		if ((!c || c->sb.version_min >= bcachefs_metadata_version_snapshot) &&
+		    bch2_bkey_format_field_overflows(f, i)) {
 			unsigned unpacked_bits = bch2_bkey_format_current.bits_per_field[i];
 			u64 unpacked_max = ~((~0ULL << 1) << (unpacked_bits - 1));
 			u64 packed_max = f->bits_per_field[i]
 				? ~((~0ULL << 1) << (f->bits_per_field[i] - 1))
 				: 0;
-			u64 field_offset = le64_to_cpu(f->field_offset[i]);
 
-			if (packed_max + field_offset < packed_max ||
-			    packed_max + field_offset > unpacked_max) {
-				prt_printf(err, "field %u too large: %llu + %llu > %llu",
-					   i, packed_max, field_offset, unpacked_max);
-				return -BCH_ERR_invalid;
-			}
+			prt_printf(err, "field %u too large: %llu + %llu > %llu",
+				   i, packed_max, le64_to_cpu(f->field_offset[i]), unpacked_max);
+			return -BCH_ERR_invalid;
 		}
 
 		bits += f->bits_per_field[i];

fs/bcachefs/bkey.h

@@ -574,6 +574,29 @@ static inline void bch2_bkey_format_add_key(struct bkey_format_state *s, const s
 
 void bch2_bkey_format_add_pos(struct bkey_format_state *, struct bpos);
 struct bkey_format bch2_bkey_format_done(struct bkey_format_state *);
+
+static inline bool bch2_bkey_format_field_overflows(struct bkey_format *f, unsigned i)
+{
+	unsigned f_bits = f->bits_per_field[i];
+	unsigned unpacked_bits = bch2_bkey_format_current.bits_per_field[i];
+	u64 unpacked_mask = ~((~0ULL << 1) << (unpacked_bits - 1));
+	u64 field_offset = le64_to_cpu(f->field_offset[i]);
+
+	if (f_bits > unpacked_bits)
+		return true;
+
+	if ((f_bits == unpacked_bits) && field_offset)
+		return true;
+
+	u64 f_mask = f_bits
+		? ~((~0ULL << (f_bits - 1)) << 1)
+		: 0;
+
+	if (((field_offset + f_mask) & unpacked_mask) < field_offset)
+		return true;
+	return false;
+}
+
 int bch2_bkey_format_invalid(struct bch_fs *, struct bkey_format *,
 			     enum bkey_invalid_flags, struct printbuf *);
 void bch2_bkey_format_to_text(struct printbuf *, const struct bkey_format *);

fs/bcachefs/move.c

@@ -975,26 +975,10 @@ static bool migrate_btree_pred(struct bch_fs *c, void *arg,
  */
 static bool bformat_needs_redo(struct bkey_format *f)
 {
-	for (unsigned i = 0; i < f->nr_fields; i++) {
-		unsigned f_bits = f->bits_per_field[i];
-		unsigned unpacked_bits = bch2_bkey_format_current.bits_per_field[i];
-		u64 unpacked_mask = ~((~0ULL << 1) << (unpacked_bits - 1));
-		u64 field_offset = le64_to_cpu(f->field_offset[i]);
-
-		if (f_bits > unpacked_bits)
-			return true;
-
-		if ((f_bits == unpacked_bits) && field_offset)
+	for (unsigned i = 0; i < f->nr_fields; i++)
+		if (bch2_bkey_format_field_overflows(f, i))
 			return true;
 
-		u64 f_mask = f_bits
-			? ~((~0ULL << (f_bits - 1)) << 1)
-			: 0;
-
-		if (((field_offset + f_mask) & unpacked_mask) < field_offset)
-			return true;
-	}
-
 	return false;
 }