linux-kernel - [PATCH 3.19.y-ckt 059/102] libfc: Fix fc_exch_recv

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Message-Id: <1442944358-1248-60-git-send-email-kamal@canonical.com>
Date:	Tue, 22 Sep 2015 10:51:55 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Bart Van Assche <bart.vanassche@...disk.com>,
	Vasu Dev <vasu.dev@...el.com>,
	James Bottomley <JBottomley@...n.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.19.y-ckt 059/102] libfc: Fix fc_exch_recv_req() error path

3.19.8-ckt7 -stable review patch.  If anyone has any objections, please let me know.

------------------

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

commit f6979adeaab578f8ca14fdd32b06ddee0d9d3314 upstream.

Due to patch "libfc: Do not invoke the response handler after
fc_exch_done()" (commit ID 7030fd62) the lport_recv() call
in fc_exch_recv_req() is passed a dangling pointer. Avoid this
by moving the fc_frame_free() call from fc_invoke_resp() to its
callers. This patch fixes the following crash:

general protection fault: 0000 [#3] PREEMPT SMP
RIP: fc_lport_recv_req+0x72/0x280 [libfc]
Call Trace:
 fc_exch_recv+0x642/0xde0 [libfc]
 fcoe_percpu_receive_thread+0x46a/0x5ed [fcoe]
 kthread+0x10a/0x120
 ret_from_fork+0x42/0x70

Signed-off-by: Bart Van Assche <bart.vanassche@...disk.com>
Signed-off-by: Vasu Dev <vasu.dev@...el.com>
Signed-off-by: James Bottomley <JBottomley@...n.com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/scsi/libfc/fc_exch.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/scsi/libfc/fc_exch.c b/drivers/scsi/libfc/fc_exch.c
index 1b3a094..30f9ef0 100644
--- a/drivers/scsi/libfc/fc_exch.c
+++ b/drivers/scsi/libfc/fc_exch.c
@@ -733,8 +733,6 @@ static bool fc_invoke_resp(struct fc_exch *ep, struct fc_seq *sp,
 	if (resp) {
 		resp(sp, fp, arg);
 		res = true;
-	} else if (!IS_ERR(fp)) {
-		fc_frame_free(fp);
 	}
 
 	spin_lock_bh(&ep->ex_lock);
@@ -1596,7 +1594,8 @@ static void fc_exch_recv_seq_resp(struct fc_exch_mgr *mp, struct fc_frame *fp)
 	 * If new exch resp handler is valid then call that
 	 * first.
 	 */
-	fc_invoke_resp(ep, sp, fp);
+	if (!fc_invoke_resp(ep, sp, fp))
+		fc_frame_free(fp);
 
 	fc_exch_release(ep);
 	return;
@@ -1695,7 +1694,8 @@ static void fc_exch_abts_resp(struct fc_exch *ep, struct fc_frame *fp)
 	fc_exch_hold(ep);
 	if (!rc)
 		fc_exch_delete(ep);
-	fc_invoke_resp(ep, sp, fp);
+	if (!fc_invoke_resp(ep, sp, fp))
+		fc_frame_free(fp);
 	if (has_rec)
 		fc_exch_timer_set(ep, ep->r_a_tov);
 	fc_exch_release(ep);
-- 
1.9.1

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