Patch "IB/srp: Avoid that duplicate responses trigger a kernel bug" has been added to the 4.4-stable tree

[<gregkh@linuxfoundation.org>]

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

    IB/srp: Avoid that duplicate responses trigger a kernel bug

to the 4.4-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:
     ib-srp-avoid-that-duplicate-responses-trigger-a-kernel-bug.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 6cb72bc1b40bb2c1750ee7a5ebade93bed49a5fb Mon Sep 17 00:00:00 2001
From: Bart Van Assche <bart.vanassche@sandisk.com>
Date: Tue, 14 Feb 2017 10:56:30 -0800
Subject: IB/srp: Avoid that duplicate responses trigger a kernel bug

From: Bart Van Assche <bart.vanassche@sandisk.com>

commit 6cb72bc1b40bb2c1750ee7a5ebade93bed49a5fb upstream.

After srp_process_rsp() returns there is a short time during which
the scsi_host_find_tag() call will return a pointer to the SCSI
command that is being completed. If during that time a duplicate
response is received, avoid that the following call stack appears:

BUG: unable to handle kernel NULL pointer dereference at           (null)
IP: srp_recv_done+0x450/0x6b0 [ib_srp]
Oops: 0000 [#1] SMP
CPU: 10 PID: 0 Comm: swapper/10 Not tainted 4.10.0-rc7-dbg+ #1
Call Trace:
 <IRQ>
 __ib_process_cq+0x4b/0xd0 [ib_core]
 ib_poll_handler+0x1d/0x70 [ib_core]
 irq_poll_softirq+0xba/0x120
 __do_softirq+0xba/0x4c0
 irq_exit+0xbe/0xd0
 smp_apic_timer_interrupt+0x38/0x50
 apic_timer_interrupt+0x90/0xa0
 </IRQ>
RIP: srp_recv_done+0x450/0x6b0 [ib_srp] RSP: ffff88046f483e20

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Israel Rukshin <israelr@mellanox.com>
Cc: Max Gurtovoy <maxg@mellanox.com>
Cc: Laurence Oberman <loberman@redhat.com>
Cc: Steve Feeley <Steve.Feeley@sandisk.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/infiniband/ulp/srp/ib_srp.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/infiniband/ulp/srp/ib_srp.c
+++ b/drivers/infiniband/ulp/srp/ib_srp.c
@@ -1795,9 +1795,11 @@ static void srp_process_rsp(struct srp_r
 		complete(&ch->tsk_mgmt_done);
 	} else {
 		scmnd = scsi_host_find_tag(target->scsi_host, rsp->tag);
-		if (scmnd) {
+		if (scmnd && scmnd->host_scribble) {
 			req = (void *)scmnd->host_scribble;
 			scmnd = srp_claim_req(ch, req, NULL, scmnd);
+		} else {
+			scmnd = NULL;
 		}
 		if (!scmnd) {
 			shost_printk(KERN_ERR, target->scsi_host,


Patches currently in stable-queue which might be from bart.vanassche@sandisk.com are

queue-4.4/ib-srp-avoid-that-duplicate-responses-trigger-a-kernel-bug.patch
queue-4.4/ib-srp-fix-race-conditions-related-to-task-management.patch