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bcachefs: Fix sb-downgrade validation

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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>
This commit is contained in:
Kent Overstreet 2024-05-25 12:38:53 -04:00
parent d509cadc3a
commit 9242a34b76
1 changed files with 10 additions and 3 deletions
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13
fs/bcachefs/sb-downgrade.c
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@ -146,10 +146,17 @@ 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 (flags & BCH_VALIDATE_write &&
((void *) &i->errors[0] > vstruct_end(&e->field) ||
(void *) downgrade_entry_next_c(i) > vstruct_end(&e->field))) {
prt_printf(err, "downgrade entry overruns end of superblock section)");
(void *) downgrade_entry_next_c(i) > vstruct_end(&e->field)) {
prt_printf(err, "downgrade entry overruns end of superblock section");
return -BCH_ERR_invalid_sb_downgrade;
}