From: Yu Kuai <yukuai3@xxxxxxxxxx> [ Upstream commit 2acf15b94d5b8ea8392c4b6753a6ffac3135cd78 ] Our syzcaller report a NULL pointer dereference: BUG: kernel NULL pointer dereference, address: 0000000000000000 PGD 116e95067 P4D 116e95067 PUD 1080b5067 PMD 0 Oops: 0010 [#1] SMP KASAN CPU: 7 PID: 592 Comm: a.out Not tainted 5.13.0-next-20210629-dirty #67 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20190727_073836-buildvm-p4 RIP: 0010:0x0 Code: Unable to access opcode bytes at RIP 0xffffffffffffffd6. RSP: 0018:ffff888114e779b8 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 1ffff110229cef39 RCX: ffffffffaa67e1aa RDX: 0000000000000000 RSI: ffff88810a58ee00 RDI: ffff8881233180b0 RBP: ffffffffac38e9c0 R08: ffffffffaa67e17e R09: 0000000000000001 R10: ffffffffb91c5557 R11: fffffbfff7238aaa R12: ffff88810a58ee00 R13: ffff888114e77aa0 R14: 0000000000000000 R15: ffff8881233180b0 FS: 00007f946163c480(0000) GS:ffff88839f1c0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffffffffffffd6 CR3: 00000001099c1000 CR4: 00000000000006e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __lookup_slow+0x116/0x2d0 ? page_put_link+0x120/0x120 ? __d_lookup+0xfc/0x320 ? d_lookup+0x49/0x90 lookup_one_len+0x13c/0x170 ? __lookup_slow+0x2d0/0x2d0 ? reiserfs_schedule_old_flush+0x31/0x130 reiserfs_lookup_privroot+0x64/0x150 reiserfs_fill_super+0x158c/0x1b90 ? finish_unfinished+0xb10/0xb10 ? bprintf+0xe0/0xe0 ? __mutex_lock_slowpath+0x30/0x30 ? __kasan_check_write+0x20/0x30 ? up_write+0x51/0xb0 ? set_blocksize+0x9f/0x1f0 mount_bdev+0x27c/0x2d0 ? finish_unfinished+0xb10/0xb10 ? reiserfs_kill_sb+0x120/0x120 get_super_block+0x19/0x30 legacy_get_tree+0x76/0xf0 vfs_get_tree+0x49/0x160 ? capable+0x1d/0x30 path_mount+0xacc/0x1380 ? putname+0x97/0xd0 ? finish_automount+0x450/0x450 ? kmem_cache_free+0xf8/0x5a0 ? putname+0x97/0xd0 do_mount+0xe2/0x110 ? path_mount+0x1380/0x1380 ? copy_mount_options+0x69/0x140 __x64_sys_mount+0xf0/0x190 do_syscall_64+0x35/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xae This is because 'root_inode' is initialized with wrong mode, and it's i_op is set to 'reiserfs_special_inode_operations'. Thus add check for 'root_inode' to fix the problem. Link: https://lore.kernel.org/r/20210702040743.1918552-1-yukuai3@xxxxxxxxxx Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx> Signed-off-by: Jan Kara <jack@xxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- fs/reiserfs/super.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/fs/reiserfs/super.c b/fs/reiserfs/super.c index ec5716dd58c2..831a542c22c6 100644 --- a/fs/reiserfs/super.c +++ b/fs/reiserfs/super.c @@ -2085,6 +2085,14 @@ static int reiserfs_fill_super(struct super_block *s, void *data, int silent) unlock_new_inode(root_inode); } + if (!S_ISDIR(root_inode->i_mode) || !inode_get_bytes(root_inode) || + !root_inode->i_size) { + SWARN(silent, s, "", "corrupt root inode, run fsck"); + iput(root_inode); + errval = -EUCLEAN; + goto error; + } + s->s_root = d_make_root(root_inode); if (!s->s_root) goto error; -- 2.30.2
