[Ocfs2-devel] [PATCH] ocfs2: check if cluster name exists before deref

[Mark Fasheh <mfasheh@suse.de>]

On Tue, Mar 25, 2014 at 01:21:58PM -0400, Sasha Levin wrote:
> Commit c74a3bdd9b "ocfs2: add clustername to cluster connection"
> is trying to strlcpy a string which was explicitly passed as NULL
> in the very same patch, triggering a NULL ptr deref.
> 
> [  640.225193] BUG: unable to handle kernel NULL pointer dereference at           (null)
> [  640.230224] IP: strlcpy (lib/string.c:388 lib/string.c:151)
> [  640.230224] PGD 82a93a067 PUD 82a93b067 PMD 0 
> [  640.230224] Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
> [  640.230224] Dumping ftrace buffer:
> [  640.230224]    (ftrace buffer empty)
> [  640.230224] Modules linked in:
> [  640.230224] CPU: 19 PID: 19426 Comm: trinity-c19 Tainted: G        W     3.14.0-rc7-next-20140325-sasha-00014-g9476368-dirty #274
> [  640.230224] task: ffff88082bc53000 ti: ffff88082b674000 task.ti: ffff88082b674000
> [  640.230224] RIP:  strlcpy (lib/string.c:388 lib/string.c:151)
> [  640.230224] RSP: 0018:ffff88082b675d88  EFLAGS: 00010296
> [  640.230224] RAX: 0000000000000007 RBX: ffffffff8853b260 RCX: 000000006f6d7366
> [  640.230224] RDX: 0000000000000011 RSI: 0000000000000000 RDI: ffff88052bcd3518  
> [  640.230224] RBP: ffff88082b675da8 R08: 00000000746e756f R09: 0000000000000000  
> [  640.230224] R10: ffff88052bcd34d0 R11: 0000000000000000 R12: ffff88052bcd3518  
> [  640.230224] R13: ffff88052c003fb8 R14: ffff88052bcd34d0 R15: 00000000ffffffea
> [  640.230224] FS:  00007f04ae7a6700(0000) GS:ffff88052cc00000(0000) knlGS:0000000000000000
> [  640.230224] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> [  640.230224] CR2: 0000000000000000 CR3: 000000082115b000 CR4: 00000000000006a0
> [  640.230224] DR0: 0000000000698000 DR1: 0000000000698000 DR2: 0000000000000000
> [  640.230224] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000602
> [  640.230224] Stack:
> [  640.230224]  ffffffff86b3c260 ffffffff8853b260 ffffffff86b3c260 ffff88052c003fb8
> [  640.230224]  ffff88082b675df8 ffffffff818a3a5d 0000000000000000 0000000700000000
> [  640.230224]  0000000000000282 ffff88052c003f48 ffff88003e6b01a0 ffff88052c0f81a0
> [  640.230224] Call Trace:
> [  640.230224]  ocfs2_cluster_connect (fs/ocfs2/stackglue.c:350)
> [  640.230224]  ocfs2_cluster_connect_agnostic (fs/ocfs2/stackglue.c:396)
> [  640.230224]  ? ocfs2_control_open (fs/ocfs2/dlmfs/userdlm.c:660)
> [  640.230224]  user_dlm_register (fs/ocfs2/dlmfs/userdlm.c:679)
> [  640.230224]  ? dlmfs_get_inode (fs/ocfs2/dlmfs/dlmfs.c:468)
> [  640.230224]  dlmfs_mkdir (fs/ocfs2/dlmfs/dlmfs.c:503)
> [  640.230224]  ? security_inode_permission (security/security.c:555)
> [  640.230224]  ? __inode_permission (fs/namei.c:414)
> [  640.230224]  vfs_mkdir (fs/namei.c:3467)
> [  640.230224]  SyS_mkdirat (fs/namei.c:3488 fs/namei.c:3472)
> [  640.230224]  tracesys (arch/x86/kernel/entry_64.S:749)  
> [  640.230224] Code: 41 c6 44 1d 00 00 48 83 c4 08 5b 4c 89 e0 41 5c 41 5d 5d c3 0f 1f 80 00 00 00 00 55 48 89 e5 41 55 41 54 49 89 fc 53 48 83 ec 08 <80> 3e 00 74 1c 48 89 f0 0f 1f 84 00 00 00 00 00 48 83 c0 01 80 
> [  640.230224] RIP  strlcpy (lib/string.c:388 lib/string.c:151)
> [  640.230224]  RSP <ffff88082b675d88>
> [  640.230224] CR2: 0000000000000000
> 
> Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
> ---
> 
> As a side note, how the hell was this new code path tested?
> It's obviously broken and there's no way it even passes
> a very basic test.

I'm not trying to 'defend' Goldwyn, or anything, but mistakes get made -
it's a fact of life. We have a review process to hopefully catch these sorts
of things, you are welcome to take part in it. In fact, if you were
willing to test and report these sorts of things to the Ocfs2-devel list
before they go upstream that would probably help prevent this sort of thing
from happening in the future.

Thanks,
	--Mark

--
Mark Fasheh