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

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

[Breno Leitao]

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>

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

[Greg Kroah-Hartman]

On Mon, Mar 09, 2026 at 03:16:13AM -0700, Breno Leitao wrote:
> From: Corey Minyard <corey@minyard.net>
> 
> [ Upstream commit f9323a44994c2ccd5e0d582bac6f2b2a662e5603 ]

This is not a valid git id in Linus's tree :(

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

[Breno Leitao]

On Mon, Mar 09, 2026 at 11:34:08AM +0100, Greg Kroah-Hartman wrote:
> On Mon, Mar 09, 2026 at 03:16:13AM -0700, Breno Leitao wrote:
> > From: Corey Minyard <corey@minyard.net>
> >
> > [ Upstream commit f9323a44994c2ccd5e0d582bac6f2b2a662e5603 ]
>
> This is not a valid git id in Linus's tree :(

Sorry about that, Greg. The correct commit is
594c11d0e1d445f580898a2b8c850f2e3f099368 ("ipmi: Fix use-after-free and
list corruption on sender error").

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

[Greg Kroah-Hartman]

On Mon, Mar 09, 2026 at 03:52:41AM -0700, Breno Leitao wrote:
> On Mon, Mar 09, 2026 at 11:34:08AM +0100, Greg Kroah-Hartman wrote:
> > On Mon, Mar 09, 2026 at 03:16:13AM -0700, Breno Leitao wrote:
> > > From: Corey Minyard <corey@minyard.net>
> > >
> > > [ Upstream commit f9323a44994c2ccd5e0d582bac6f2b2a662e5603 ]
> >
> > This is not a valid git id in Linus's tree :(
> 
> Sorry about that, Greg. The correct commit is
> 594c11d0e1d445f580898a2b8c850f2e3f099368 ("ipmi: Fix use-after-free and
> list corruption on sender error").
> 

Great, can you resend it?  And also let us know what branches you want
this applied to?

thanks,

greg k-h