Re: [PATCH] drm/xe: keep process name fallback for diagnostics

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] Lockless access to `task->comm` via `kstrdup()` creates a TOCTOU race leading to a non-null-terminated string and an out-of-bounds read.
--

commit f329e0d91af948bfcb07b90ac00f44ede0a2f8fc
Author: Ruoyu Wang <ruoyuw560@gmail.com>

drm/xe: keep process name fallback for diagnostics

This commit addresses an issue where diagnostic paths would use a NULL
pointer for a process name if allocation failed during file open. It keeps
the "no process" fallback unless the process name was successfully
allocated.

[ ... ]

> diff --git a/drivers/gpu/drm/xe/xe_guc_submit.c b/drivers/gpu/drm/xe/xe_guc_submit.c
> index 4b247a3019d2d..697faf0f1048b 100644
> --- a/drivers/gpu/drm/xe/xe_guc_submit.c
> +++ b/drivers/gpu/drm/xe/xe_guc_submit.c
> @@ -1590,7 +1590,8 @@ guc_exec_queue_timedout_job(struct drm_sched_job *drm_job)
>  	}
>  
>  	if (q->vm && q->vm->xef) {
> -		process_name = q->vm->xef->process_name;
> +		if (q->vm->xef->process_name)
> +			process_name = q->vm->xef->process_name;
>  		pid = q->vm->xef->pid;
>  	}

[Severity: High]
This is a pre-existing issue, but does using this string in formatting
functions risk an out-of-bounds memory read?

Looking at xe_file_open() in drivers/gpu/drm/xe/xe_device.c, task->comm is
directly passed to kstrdup() without holding task_lock(task):

    xef->process_name = kstrdup(task->comm, GFP_KERNEL);

Since task->comm can be modified concurrently by userspace via
prctl(PR_SET_NAME), kstrdup() can compute a short length during its internal
strlen() call, but copy characters from a longer replacement string during
memcpy(). This results in a heap buffer missing a null terminator.

When process_name is subsequently passed to xe_gt_notice() further down in
this function and printed via the %s format specifier:

    xe_gt_notice(guc_to_gt(guc),
                 "Timedout job: seqno=%u, lrc_seqno=%u, guc_id=%d, flags=0x%lx in %s [%d]",
                 xe_sched_job_seqno(job), xe_sched_job_lrc_seqno(job),
                 q->guc->id, q->flags, process_name, pid);

Can this trigger an out-of-bounds read of adjacent slab memory, potentially
leading to KASAN panics or kernel memory disclosure?

Could the string copying in xe_file_open() be safely changed to use
get_task_comm() instead?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260609162057.5-1-ruoyuw560@gmail.com?part=1