Patch "net/smc: fix NULL pointer dereference on sock_create_kern() error path" has been added to the 4.15-stable tree

This is a note to let you know that I've just added the patch titled

net/smc: fix NULL pointer dereference on sock_create_kern() error path

to the 4.15-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:
net-smc-fix-null-pointer-dereference-on-sock_create_kern-error-path.patch
and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Davide Caratti <[email protected]>
Date: Wed, 28 Feb 2018 12:44:09 +0100
Subject: net/smc: fix NULL pointer dereference on sock_create_kern() error path

From: Davide Caratti <[email protected]>

commit a5dcb73b96a9d21431048bdaac02d9e96f386da3 upstream.

when sock_create_kern(..., a) returns an error, 'a' might not be a valid pointer, so it shouldn't be dereferenced to read a->sk->sk_sndbuf and and a->sk->sk_rcvbuf; not doing that caused the following crash:

general protection fault: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
    (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 4254 Comm: syzkaller919713 Not tainted 4.16.0-rc1+ #18
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
RIP: 0010:smc_create+0x14e/0x300 net/smc/af_smc.c:1410
RSP: 0018:ffff8801b06afbc8 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: ffff8801b63457c0 RCX: ffffffff85a3e746
RDX: 0000000000000004 RSI: 00000000ffffffff RDI: 0000000000000020
RBP: ffff8801b06afbf0 R08: 00000000000007c0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: ffff8801b6345c08 R14: 00000000ffffffe9 R15: ffffffff8695ced0
FS:  0000000001afb880(0000) GS:ffff8801db200000(0000)
knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000040 CR3: 00000001b0721004 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  __sock_create+0x4d4/0x850 net/socket.c:1285
  sock_create net/socket.c:1325 [inline]
  SYSC_socketpair net/socket.c:1409 [inline]
  SyS_socketpair+0x1c0/0x6f0 net/socket.c:1366
  do_syscall_64+0x282/0x940 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x26/0x9b
RIP: 0033:0x4404b9
RSP: 002b:00007fff44ab6908 EFLAGS: 00000246 ORIG_RAX: 0000000000000035
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000004404b9
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 000000000000002b
RBP: 00007fff44ab6910 R08: 0000000000000002 R09: 00007fff44003031
R10: 0000000020000040 R11: 0000000000000246 R12: ffffffffffffffff
R13: 0000000000000006 R14: 0000000000000000 R15: 0000000000000000
Code: 48 c1 ea 03 80 3c 02 00 0f 85 b3 01 00 00 4c 8b a3 48 04 00 00 48

b8
00 00 00 00 00 fc ff df 49 8d 7c 24 20 48 89 fa 48 c1 ea 03 <80> 3c 02 00
0f 85 82 01 00 00 4d 8b 7c 24 20 48 b8 00 00 00 00

RIP: smc_create+0x14e/0x300 net/smc/af_smc.c:1410 RSP: ffff8801b06afbc8

---
 net/smc/af_smc.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

@@ -1369,8 +1369,10 @@ static int smc_create(struct net *net, s
 	smc->use_fallback = false; /* assume rdma capability first */
 	rc = sock_create_kern(net, PF_INET, SOCK_STREAM,
 			      IPPROTO_TCP, &smc->clcsock);
-	if (rc)
+	if (rc) {
 		sk_common_release(sk);
+		goto out;
+	}
 	smc->sk.sk_sndbuf = max(smc->clcsock->sk->sk_sndbuf, SMC_BUF_MIN_SIZE);
 	smc->sk.sk_rcvbuf = max(smc->clcsock->sk->sk_rcvbuf, SMC_BUF_MIN_SIZE);
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.15/net-smc-fix-null-pointer-dereference-on-sock_create_kern-error-path.patch