linux-kernel - [PATCH 4.20 126/127] ipmi: Prevent use-after-free in deliver

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Message-Id: <20190124190217.277761137@linuxfoundation.org>
Date:   Thu, 24 Jan 2019 20:21:12 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Fred Klassen <fklassen@...neta.com>,
        Corey Minyard <cminyard@...sta.com>
Subject: [PATCH 4.20 126/127] ipmi: Prevent use-after-free in deliver_response

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

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

From: Fred Klassen <fklassen@...neta.com>

commit 479d6b39b9e0d2de648ebf146f23a1e40962068f upstream.

Some IPMI modules (e.g. ibmpex_msg_handler()) will have ipmi_usr_hdlr
handlers that call ipmi_free_recv_msg() directly. This will essentially
kfree(msg), leading to use-after-free.

This does not happen in the ipmi_devintf module, which will queue the
message and run ipmi_free_recv_msg() later.

BUG: KASAN: use-after-free in deliver_response+0x12f/0x1b0
Read of size 8 at addr ffff888a7bf20018 by task ksoftirqd/3/27
CPU: 3 PID: 27 Comm: ksoftirqd/3 Tainted: G           O      4.19.11-amd64-ani99-debug #12.0.1.601133+pv
Hardware name: AppNeta r1000/X11SPW-TF, BIOS 2.1a-AP 09/17/2018
Call Trace:
dump_stack+0x92/0xeb
print_address_description+0x73/0x290
kasan_report+0x258/0x380
deliver_response+0x12f/0x1b0
? ipmi_free_recv_msg+0x50/0x50
deliver_local_response+0xe/0x50
handle_one_recv_msg+0x37a/0x21d0
handle_new_recv_msgs+0x1ce/0x440
...

Allocated by task 9885:
kasan_kmalloc+0xa0/0xd0
kmem_cache_alloc_trace+0x116/0x290
ipmi_alloc_recv_msg+0x28/0x70
i_ipmi_request+0xb4a/0x1640
ipmi_request_settime+0x1b8/0x1e0
...

Freed by task 27:
__kasan_slab_free+0x12e/0x180
kfree+0xe9/0x280
deliver_response+0x122/0x1b0
deliver_local_response+0xe/0x50
handle_one_recv_msg+0x37a/0x21d0
handle_new_recv_msgs+0x1ce/0x440
tasklet_action_common.isra.19+0xc4/0x250
__do_softirq+0x11f/0x51f

Fixes: e86ee2d44b44 ("ipmi: Rework locking and shutdown for hot remove")
Cc: stable@...r.kernel.org # 4.18
Signed-off-by: Fred Klassen <fklassen@...neta.com>
Signed-off-by: Corey Minyard <cminyard@...sta.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/char/ipmi/ipmi_msghandler.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/char/ipmi/ipmi_msghandler.c
+++ b/drivers/char/ipmi/ipmi_msghandler.c
@@ -894,7 +894,7 @@ static int deliver_response(struct ipmi_

 		if (user) {
 			user->handler->ipmi_recv_hndl(msg, user->handler_data);
-			release_ipmi_user(msg->user, index);
+			release_ipmi_user(user, index);
 		} else {
 			/* User went away, give up. */
 			ipmi_free_recv_msg(msg);