From fe0a145e54be7256a1e9fc986b18b618cdf60b4a Mon Sep 17 00:00:00 2001 From: Kent Overstreet Date: Sat, 25 May 2024 12:38:53 -0400 Subject: [PATCH] bcachefs: Fix sb-downgrade validation BugLink: https://bugs.launchpad.net/bugs/2076435 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 Signed-off-by: Greg Kroah-Hartman Signed-off-by: Portia Stephens Signed-off-by: Roxana Nicolescu --- fs/bcachefs/sb-downgrade.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/fs/bcachefs/sb-downgrade.c b/fs/bcachefs/sb-downgrade.c index 63bdcad73af3..511bf75c6dd6 100644 --- a/fs/bcachefs/sb-downgrade.c +++ b/fs/bcachefs/sb-downgrade.c @@ -137,6 +137,14 @@ static int bch2_sb_downgrade_validate(struct bch_sb *sb, struct bch_sb_field *f, 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)",