[PATCH stable] ipmi: Fix use-after-free and list corruption on sender error

[Breno Leitao <leitao@debian.org>]

From: Corey Minyard <corey@minyard.net>

[ Upstream commit f9323a44994c2ccd5e0d582bac6f2b2a662e5603 ]

The analysis from Breno:

When the SMI sender returns an error, smi_work() delivers an error
response but then jumps back to restart without cleaning up properly:

1. intf->curr_msg is not cleared, so no new message is pulled
2. newmsg still points to the message, causing sender() to be called
   again with the same message
3. If sender() fails again, deliver_err_response() is called with
   the same recv_msg that was already queued for delivery

This causes list_add corruption ("list_add double add") because the
recv_msg is added to the user_msgs list twice. Subsequently, the
corrupted list leads to use-after-free when the memory is freed and
reused, and eventually a NULL pointer dereference when accessing
recv_msg->done.

The buggy sequence:

  sender() fails
    -> deliver_err_response(recv_msg)  // recv_msg queued for delivery
    -> goto restart                    // curr_msg not cleared!
  sender() fails again (same message!)
    -> deliver_err_response(recv_msg)  // tries to queue same recv_msg
    -> LIST CORRUPTION

Fix this by freeing the message and setting it to NULL on a send error.
Also, always free the newmsg on a send error, otherwise it will leak.

Reported-by: Breno Leitao <leitao@debian.org>
Closes: https://lore.kernel.org/lkml/20260127-ipmi-v1-0-ba5cc90f516f@debian.org/
Fixes: 9cf93a8fa9513 ("ipmi: Allow an SMI sender to return an error")
Cc: stable@vger.kernel.org # 4.18
Reviewed-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Corey Minyard <corey@minyard.net>
Signed-off-by: Breno Leitao <leitao@debian.org>
---
 drivers/char/ipmi/ipmi_msghandler.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
index 0a886399f9daf..5ed8e95589fb7 100644
--- a/drivers/char/ipmi/ipmi_msghandler.c
+++ b/drivers/char/ipmi/ipmi_msghandler.c
@@ -4848,8 +4848,15 @@ static void smi_work(struct work_struct *t)
 			if (newmsg->recv_msg)
 				deliver_err_response(intf,
 						     newmsg->recv_msg, cc);
-			else
-				ipmi_free_smi_msg(newmsg);
+			if (!run_to_completion)
+				spin_lock_irqsave(&intf->xmit_msgs_lock,
+						  flags);
+			intf->curr_msg = NULL;
+			if (!run_to_completion)
+				spin_unlock_irqrestore(&intf->xmit_msgs_lock,
+						       flags);
+			ipmi_free_smi_msg(newmsg);
+			newmsg = NULL;
 			goto restart;
 		}
 	}

---
base-commit: 6258e292d7463f96d0f06dff2a39093a54c9d16f
change-id: 20260309-ipmi_stable-bde1bbf58536

Best regards,
--  
Breno Leitao <leitao@debian.org>