From 105c78e12468413e426625831faa7db4284e1fec Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Tue, 1 Nov 2022 22:33:12 -0700 Subject: [PATCH] ext4: don't allow journal inode to have encrypt flag Mounting a filesystem whose journal inode has the encrypt flag causes a NULL dereference in fscrypt_limit_io_blocks() when the 'inlinecrypt' mount option is used. The problem is that when jbd2_journal_init_inode() calls bmap(), it eventually finds its way into ext4_iomap_begin(), which calls fscrypt_limit_io_blocks(). fscrypt_limit_io_blocks() requires that if the inode is encrypted, then its encryption key must already be set up. That's not the case here, since the journal inode is never "opened" like a normal file would be. Hence the crash. A reproducer is: mkfs.ext4 -F /dev/vdb debugfs -w /dev/vdb -R "set_inode_field <8> flags 0x80808" mount /dev/vdb /mnt -o inlinecrypt To fix this, make ext4 consider journal inodes with the encrypt flag to be invalid. (Note, maybe other flags should be rejected on the journal inode too. For now, this is just the minimal fix for the above issue.) I've marked this as fixing the commit that introduced the call to fscrypt_limit_io_blocks(), since that's what made an actual crash start being possible. But this fix could be applied to any version of ext4 that supports the encrypt feature. Reported-by: syzbot+ba9dac45bc76c490b7c3@syzkaller.appspotmail.com Fixes: 38ea50daa7a4 ("ext4: support direct I/O with fscrypt using blk-crypto") Cc: stable@vger.kernel.org Signed-off-by: Eric Biggers Link: https://lore.kernel.org/r/20221102053312.189962-1-ebiggers@kernel.org Signed-off-by: Theodore Ts'o Cc: stable@kernel.org --- fs/ext4/super.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 6f944f5..9185131 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -5723,7 +5723,7 @@ static struct inode *ext4_get_journal_inode(struct super_block *sb, ext4_debug("Journal inode found at %p: %lld bytes\n", journal_inode, journal_inode->i_size); - if (!S_ISREG(journal_inode->i_mode)) { + if (!S_ISREG(journal_inode->i_mode) || IS_ENCRYPTED(journal_inode)) { ext4_msg(sb, KERN_ERR, "invalid journal inode"); iput(journal_inode); return NULL; -- 2.7.4