Patch "scsi: scsi_transport_iscsi: fix the issue that iscsi_if_rx doesn't parse nlmsg properly" has been added to the 4.9-stable tree

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

scsi: scsi_transport_iscsi: fix the issue that iscsi_if_rx doesn't parse nlmsg properly

to the 4.9-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:
scsi-scsi_transport_iscsi-fix-the-issue-that-iscsi_if_rx-doesn-t-parse-nlmsg-properly.patch
and it can be found in the queue-4.9 subdirectory.

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

From: Xin Long <[email protected]>
Date: Sun, 27 Aug 2017 20:25:26 +0800
Subject: scsi: scsi_transport_iscsi: fix the issue that iscsi_if_rx doesn't parse nlmsg properly

From: Xin Long <[email protected]>

commit c88f0e6b06f4092995688211a631bb436125d77b upstream.

ChunYu found a kernel crash by syzkaller:

[  651.617875] kasan: CONFIG_KASAN_INLINE enabled
[  651.618217] kasan: GPF could be caused by NULL-ptr deref or user memory access
[  651.618731] general protection fault: 0000 [#1] SMP KASAN
[  651.621543] CPU: 1 PID: 9539 Comm: scsi Not tainted 4.11.0.cov #32
[  651.621938] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
[  651.622309] task: ffff880117780000 task.stack: ffff8800a3188000
[  651.622762] RIP: 0010:skb_release_data+0x26c/0x590
[...]
[  651.627260] Call Trace:
[  651.629156]  skb_release_all+0x4f/0x60
[  651.629450]  consume_skb+0x1a5/0x600
[  651.630705]  netlink_unicast+0x505/0x720
[  651.632345]  netlink_sendmsg+0xab2/0xe70
[  651.633704]  sock_sendmsg+0xcf/0x110
[  651.633942]  ___sys_sendmsg+0x833/0x980
[  651.637117]  __sys_sendmsg+0xf3/0x240
[  651.638820]  SyS_sendmsg+0x32/0x50
[  651.639048]  entry_SYSCALL_64_fastpath+0x1f/0xc2

It's caused by skb_shared_info at the end of sk_buff was overwritten by ISCSI_KEVENT_IF_ERROR when parsing nlmsg info from skb in iscsi_if_rx.

During the loop if skb->len == nlh->nlmsg_len and both are sizeof(*nlh), ev = nlmsg_data(nlh) will acutally get skb_shinfo(SKB) instead and set a new value to skb_shinfo(SKB)->nr_frags by ev->type.

This patch is to fix it by checking nlh->nlmsg_len properly there to avoid over accessing sk_buff.

---
 drivers/scsi/scsi_transport_iscsi.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -3696,7 +3696,7 @@ iscsi_if_rx(struct sk_buff *skb)
 		uint32_t group;
 
 		nlh = nlmsg_hdr(skb);
-		if (nlh->nlmsg_len < sizeof(*nlh) ||
+		if (nlh->nlmsg_len < sizeof(*nlh) + sizeof(*ev) ||
 		    skb->len < nlh->nlmsg_len) {
 			break;
 		}

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

queue-4.9/scsi-scsi_transport_iscsi-fix-the-issue-that-iscsi_if_rx-doesn-t-parse-nlmsg-properly.patch