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reiserfs: add check for invalid 1st journal block

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syzbot reported divide error in reiserfs.
The problem was in incorrect journal 1st block.

Syzbot's reproducer manualy generated wrong superblock
with incorrect 1st block. In journal_init() wasn't
any checks about this particular case.

For example, if 1st journal block is before superblock
1st block, it can cause zeroing important superblock members
in do_journal_end().

Link: https://lore.kernel.org/r/20210517121545.29645-1-paskripkin@gmail.com
Reported-by: syzbot+0ba9909df31c6a36974d@syzkaller.appspotmail.com
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
This commit is contained in:
Pavel Skripkin 2021-05-17 15:15:45 +03:00 committed by Jan Kara
parent 5b9fedb31e
commit a149127be5
1 changed files with 14 additions and 0 deletions
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14
fs/reiserfs/journal.c
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@ -2758,6 +2758,20 @@ int journal_init(struct super_block *sb, const char *j_dev_name,
goto free_and_return;
}
/*
* Sanity check to see if journal first block is correct.
* If journal first block is invalid it can cause
* zeroing important superblock members.
*/
if (!SB_ONDISK_JOURNAL_DEVICE(sb) &&
SB_ONDISK_JOURNAL_1st_BLOCK(sb) < SB_JOURNAL_1st_RESERVED_BLOCK(sb)) {
reiserfs_warning(sb, "journal-1393",
"journal 1st super block is invalid: 1st reserved block %d, but actual 1st block is %d",
SB_JOURNAL_1st_RESERVED_BLOCK(sb),
SB_ONDISK_JOURNAL_1st_BLOCK(sb));
goto free_and_return;
}
if (journal_init_dev(sb, journal, j_dev_name) != 0) {
reiserfs_warning(sb, "sh-462",
"unable to initialize journal device");