6.9-stable review patch. If anyone has any objections, please let me know.
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From: Kent Overstreet kent.overstreet@linux.dev
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@linux.dev Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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)",