This is a note to let you know that I've just added the patch titled reiserfs: add check for invalid 1st journal block to the 5.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: reiserfs-add-check-for-invalid-1st-journal-block.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit b025a7bbb915d088d2a3afd88da94623839de63b Author: Pavel Skripkin <paskripkin@xxxxxxxxx> Date: Mon May 17 15:15:45 2021 +0300 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@xxxxxxxxx Reported-by: syzbot+0ba9909df31c6a36974d@xxxxxxxxxxxxxxxxxxxxxxxxx Signed-off-by: Pavel Skripkin <paskripkin@xxxxxxxxx> Signed-off-by: Jan Kara <jack@xxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/fs/reiserfs/journal.c b/fs/reiserfs/journal.c index 4b3e3e73b512..09ad022a78a5 100644 --- a/fs/reiserfs/journal.c +++ b/fs/reiserfs/journal.c @@ -2763,6 +2763,20 @@ 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");