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>

1 files changed, 23 insertions, 0 deletions

diff --git a/fs/bcachefs/bkey.h b/fs/bcachefs/bkey.h
index 3a45d128f608..1bb0bd4371b0 100644
--- a/fs/bcachefs/bkey.h
+++ b/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 *);