Re: [PATCH] drm/xe/guc: Fix invalid kfree() call via __cleanup on pointer

[Thomas Huth <thuth@redhat.com>]

On 17/06/2026 16.26, Wentao Liang wrote:
> The variable `buf` in `fast_req_dump()` is declared with
> `__cleanup(kfree)`, which passes `&buf` (the stack address of the
> pointer variable) to kfree() rather than the heap address stored
> in `buf`.  This would cause an invalid free of a stack address,
> leading to memory corruption or a crash.
> 
> `__cleanup(func)` is designed for value-typed variables where the
> cleanup function should receive a pointer to the variable.  For
> heap-allocated pointers, `__free(kfree)` must be used instead,
> since DEFINE_FREE creates a wrapper that correctly dereferences
> the pointer before passing it to kfree().
> 
> This is the same class of bug recorded in CVE-2026-45959 and fixed by
> commit d5abcc33ee76 ("crypto: ccp - Fix a crash due to incorrect
> cleanup usage of kfree").
> 
> Fixes: ea944d57eac7 ("drm/xe/guc_ct: Cleanup ifdef'ry")
> Cc: stable@vger.kernel.org
> Signed-off-by: Wentao Liang <vulab@iscas.ac.cn>
> ---
>   drivers/gpu/drm/xe/xe_guc_ct.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_guc_ct.c b/drivers/gpu/drm/xe/xe_guc_ct.c
> index a11cff7a20be..73867a5cbe3a 100644
> --- a/drivers/gpu/drm/xe/xe_guc_ct.c
> +++ b/drivers/gpu/drm/xe/xe_guc_ct.c
> @@ -116,7 +116,7 @@ static void fast_req_dump(struct xe_guc_ct *ct, u16 fence, unsigned int slot)
>   {
>   	struct xe_gt *gt = ct_to_gt(ct);
>   #if IS_ENABLED(CONFIG_DRM_XE_DEBUG_GUC)
> -	char *buf __cleanup(kfree) = kmalloc(SZ_4K, GFP_NOWAIT);
> +	char *buf __free(kfree) = kmalloc(SZ_4K, GFP_NOWAIT);
>   
>   	if (buf && stack_depot_snprint(ct->fast_req[slot].stack, buf, SZ_4K, 0))
>   		xe_gt_err(gt, "Fence 0x%x was used by action %#04x sent at:\n%s\n",

Reviewed-by: Thomas Huth <thuth@redhat.com>