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Commit 03aec2c1 authored by Pavel Skripkin's avatar Pavel Skripkin Committed by Greg Kroah-Hartman
Browse files

reiserfs: add check for invalid 1st journal block 

[ 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: default avatar <syzbot+0ba9909df31c6a36974d@syzkaller.appspotmail.com>
Signed-off-by: default avatarPavel Skripkin <paskripkin@gmail.com>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 1137d57d

fs/reiserfs/journal.c

+14 −0
Original line number Diff line number Diff line
@@ -2766,6 +2766,20 @@ 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");