6.9-stable review patch. If anyone has any objections, please let me know.
------------------
From: Kent Overstreet <kent.overstreet@xxxxxxxxx>
commit 9242a34b760648b722f4958749ad83ef7d0f7525 upstream.
Superblock downgrade entries are only two byte aligned, but section
sizes are 8 byte aligned, which means we have to be careful about
overrun checks; an entry that crosses the end of the section is allowed
(and ignored) as long as it has zero errors.
Signed-off-by: Kent Overstreet <kent.overstreet@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/bcachefs/sb-downgrade.c | 8 ++++++++
1 file changed, 8 insertions(+)
--- a/fs/bcachefs/sb-downgrade.c
+++ b/fs/bcachefs/sb-downgrade.c
@@ -146,6 +146,14 @@ static int bch2_sb_downgrade_validate(st
for (const struct bch_sb_field_downgrade_entry *i = e->entries;
(void *) i < vstruct_end(&e->field);
i = downgrade_entry_next_c(i)) {
+ /*
+ * Careful: sb_field_downgrade_entry is only 2 byte aligned, but
+ * section sizes are 8 byte aligned - an empty entry spanning
+ * the end of the section is allowed (and ignored):
+ */
+ if ((void *) &i->errors[0] > vstruct_end(&e->field))
+ break;
+
if (BCH_VERSION_MAJOR(le16_to_cpu(i->version)) !=
BCH_VERSION_MAJOR(le16_to_cpu(sb->version))) {
prt_printf(err, "downgrade entry with mismatched major version (%u != %u)",
