linux-kernel - [PATCH] ipmi: Prevent use-after-free in deliver

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Message-Id: <09133030-238B-475F-94BC-B48827812714@appneta.com>
Date:   Fri, 18 Jan 2019 15:10:39 -0800
From:   Fred Klassen <fklassen@...neta.com>
To:     "Corey Minyard (supporter:IPMI SUBSYSTEM)" <minyard@....org>,
        "Arnd Bergmann (supporter:CHAR and MISC DRIVERS)" <arnd@...db.de>,
        "Greg Kroah-Hartman (supporter:CHAR and MISC DRIVERS)" 
        <gregkh@...uxfoundation.org>,
        "moderated list:IPMI SUBSYSTEM" 
        <openipmi-developer@...ts.sourceforge.net>,
        open list <linux-kernel@...r.kernel.org>
Cc:     stable@...r.kernel.org
Subject: [PATCH] ipmi: Prevent use-after-free in deliver_response

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: e86ee2d44b4 ("ipmi: Rework locking and shutdown for hot remove")
Signed-off-by: Fred Klassen <fklassen@...neta.com>

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

diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
index 7fc9612070a1..fbf93c2d6c05 100644
--- a/drivers/char/ipmi/ipmi_msghandler.c
+++ b/drivers/char/ipmi/ipmi_msghandler.c
@@ -883,7 +883,7 @@ static int deliver_response(struct ipmi_smi *intf, struct ipmi_recv_msg *msg)

 		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);
-- 
2.11.0