Re: [PATCH] misc: mei: fix race condition between client teardown and read completion

["gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>]

On Sun, Aug 23, 2026 at 01:26:09PM +0000, nirbhayykumarr@proton.me wrote:
> In mei_release(), a host client is torn down upon close(). During this
> teardown sequence, mei_cl_disconnect() is invoked, which releases
> dev->device_lock while waiting for the firmware response.
> 
> If an in-flight read request was previously submitted, an incoming
> completion interrupt processed concurrently by the MEI interrupt
> handler can add a completed callback into cl->rd_completed via
> mei_cl_add_rd_completed().
> 
> Because mei_cl_flush_queues(cl, NULL) was invoked before mei_cl_unlink(cl),
> an incoming completion callback can slip into cl->rd_completed after the
> flush has completed but before the client is unlinked from dev->file_list.
> When mei_cl_unlink() is subsequently called, the invariant check at
> drivers/misc/mei/client.c:698 triggers:
> 
>   WARN_ON(!list_empty(&cl->rd_completed) ||
>           !list_empty(&cl->rd_pending) ||
>           !list_empty(&cl->link));
> 
> Call trace:
>   WARNING: CPU: 2 PID: 5056 at drivers/misc/mei/client.c:698 mei_cl_unlink+0xaa/0x140 [mei]
>   RIP: 0010:mei_cl_unlink+0xaa/0x140 [mei]
>   Call Trace:
>    <TASK>
>    mei_release+0x202/0x270 [mei]
>    __fput+0x105/0x2e0
>    __x64_sys_close+0x90/0x140
>    do_syscall_64+0xaa/0x660
>    entry_SYSCALL_64_after_hwframe+0x77/0x7f
>    </TASK>
> 
> Immediately following mei_cl_unlink(), mei_release() calls kfree(cl).
> If any remaining or deferred callback references the freed client, a
> use-after-free occurs.
> 
> Fix this by flushing queues after unlinking the client from dev->file_list
> inside mei_cl_unlink(), preventing concurrent IRQ completions from
> populating the client's completed queue during teardown.
> 
> Reported-by: Nirbhay Kumar <nirbhayykumarr@proton.me>
> Signed-off-by: Nirbhay Kumar <nirbhayykumarr@proton.me>

No need for Reported-by as you authored and signed off on this.

And did you forget an Assisted-by: tag?

and what commit id does this fix?

Also, no need to attach this at all, just send it using git send-email
as-is.

thanks,

greg k-h