From a149127be52fa7eaf5b3681a0317a2bbb772d5a9 Mon Sep 17 00:00:00 2001
From: Pavel Skripkin <paskripkin@gmail.com>
Date: Mon, 17 May 2021 15:15:45 +0300
Subject: [PATCH] reiserfs: add check for invalid 1st journal block
Git-commit: a149127be52fa7eaf5b3681a0317a2bbb772d5a9
Patch-mainline: v5.14-rc1
References: git-fixes
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>
Acked-by: Anthony Iliopoulos <ailiop@suse.com>
---
fs/reiserfs/journal.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/fs/reiserfs/journal.c b/fs/reiserfs/journal.c
index 9edc8e2b154e..0834b101c316 100644
--- a/fs/reiserfs/journal.c
+++ b/fs/reiserfs/journal.c
@@ -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");
--
2.35.3