From: Pavel Skripkin paskripkin@gmail.com
stable inclusion from linux-4.19.198 commit 47b4b8f0d3780959a15e0118da83c42c688d14e6
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[ Upstream commit a149127be52fa7eaf5b3681a0317a2bbb772d5a9 ]
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 Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- fs/reiserfs/journal.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+)
diff --git a/fs/reiserfs/journal.c b/fs/reiserfs/journal.c index 8a76f9d14bc66..78be6dbcd7627 100644 --- a/fs/reiserfs/journal.c +++ b/fs/reiserfs/journal.c @@ -2772,6 +2772,20 @@ 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");