[PATCH 4.6 081/100] Fixing oops in callback path

Greg Kroah-Hartman
2016-05-30T21:11:23Z

From: Olga Kornievskaia <kolga@netapp.com>

commit c2985d001d2fb77357aeae675545893b61c50044 upstream.

Commit 80f9642724af5 ("NFSv4.x: Enforce the ca_maxreponsesize_cached
on the back channel") causes an oops when it receives a callback with
cachethis=yes.

[ 109.667378] BUG: unable to handle kernel NULL pointer dereference at 00000000000002c8
[ 109.669476] IP: [<ffffffffa08a3e68>] nfs4_callback_compound+0x4f8/0x690 [nfsv4]
[ 109.671216] PGD 0
[ 109.671736] Oops: 0000 [#1] SMP
[ 109.705427] CPU: 1 PID: 3579 Comm: nfsv4.1-svc Not tainted 4.5.0-rc1+ #1
[ 109.706987] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 05/20/2014
[ 109.709468] task: ffff8800b4408000 ti: ffff88008448c000 task.ti: ffff88008448c000
[ 109.711207] RIP: 0010:[<ffffffffa08a3e68>] [<ffffffffa08a3e68>] nfs4_callback_compound+0x4f8/0x690 [nfsv4]
[ 109.713521] RSP: 0018:ffff88008448fca0 EFLAGS: 00010286
[ 109.714762] RAX: ffff880081ee202c RBX: ffff8800b7b5b600 RCX: 0000000000000001
[ 109.716427] RDX: 0000000000000008 RSI: 0000000000000008 RDI: 0000000000000000
[ 109.718091] RBP: ffff88008448fda8 R08: 0000000000000000 R09: 000000000b000000
[ 109.719757] R10: ffff880137786000 R11: ffff8800b7b5b600 R12: 0000000001000000
[ 109.721415] R13: 0000000000000002 R14: 0000000053270000 R15: 000000000000000b
[ 109.723061] FS: 0000000000000000(0000) GS:ffff880139640000(0000) knlGS:0000000000000000
[ 109.724931] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 109.726278] CR2: 00000000000002c8 CR3: 0000000034d50000 CR4: 00000000001406e0
[ 109.727972] Stack:
[ 109.728465] ffff880081ee202c ffff880081ee201c 000000008448fcc0 ffff8800baccb800
[ 109.730349] ffff8800baccc800 ffffffffa08d0380 0000000000000000 0000000000000000
[ 109.732211] ffff8800b7b5b600 0000000000000001 ffffffff81d073c0 ffff880081ee3090
[ 109.734056] Call Trace:
[ 109.734657] [<ffffffffa03795d4>] svc_process_common+0x5c4/0x6c0 [sunrpc]
[ 109.736267] [<ffffffffa0379a4c>] bc_svc_process+0x1fc/0x360 [sunrpc]
[ 109.737775] [<ffffffffa08a2c2c>] nfs41_callback_svc+0x10c/0x1d0 [nfsv4]
[ 109.739335] [<ffffffff810cb380>] ? prepare_to_wait_event+0xf0/0xf0
[ 109.740799] [<ffffffffa08a2b20>] ? nfs4_callback_svc+0x50/0x50 [nfsv4]
[ 109.742349] [<ffffffff810a6998>] kthread+0xd8/0xf0
[ 109.743495] [<ffffffff810a68c0>] ? kthread_park+0x60/0x60
[ 109.744776] [<ffffffff816abc4f>] ret_from_fork+0x3f/0x70
[ 109.746037] [<ffffffff810a68c0>] ? kthread_park+0x60/0x60
[ 109.747324] Code: cc 45 31 f6 48 8b 85 00 ff ff ff 44 89 30 48 8b 85 f8 fe ff ff 44 89 20 48 8b 9d 38 ff ff ff 48 8b bd 30 ff ff ff 48 85 db 74 4c <4c> 8b af c8 02 00 00 4d 8d a5 08 02 00 00 49 81 c5 98 02 00 00
[ 109.754361] RIP [<ffffffffa08a3e68>] nfs4_callback_compound+0x4f8/0x690 [nfsv4]
[ 109.756123] RSP <ffff88008448fca0>
[ 109.756951] CR2: 00000000000002c8
[ 109.757738] ---[ end trace 2b8555511ab5dfb4 ]---
[ 109.758819] Kernel panic - not syncing: Fatal exception
[ 109.760126] Kernel Offset: disabled
[ 118.938934] ---[ end Kernel panic - not syncing: Fatal exception

It doesn't unlock the table nor does it set the cps->clp pointer which
is later needed by nfs4_cb_free_slot().

Fixes: 80f9642724af5 ("NFSv4.x: Enforce the ca_maxresponsesize_cached ...")
Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/nfs/callback_proc.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

--- a/fs/nfs/callback_proc.c
+++ b/fs/nfs/callback_proc.c
@@ -500,8 +500,10 @@ __be32 nfs4_callback_sequence(struct cb_
cps->slot = slot;

/* The ca_maxresponsesize_cached is 0 with no DRC */
- if (args->csa_cachethis != 0)
- return htonl(NFS4ERR_REP_TOO_BIG_TO_CACHE);
+ if (args->csa_cachethis != 0) {
+ status = htonl(NFS4ERR_REP_TOO_BIG_TO_CACHE);
+ goto out_unlock;
+ }

/*
* Check for pending referring calls. If a match is found, a