-----Original Message-----
From: Intel-gfx <intel-gfx-boun...@lists.freedesktop.org> On Behalf Of
Krzysztof Karas
Sent: Monday, August 4, 2025 12:57 AM
To: intel-gfx@lists.freedesktop.org
Cc: Chris Wilson <chris.p.wil...@linux.intel.com>; Andi Shyti
<andi.sh...@linux.intel.com>; Brzezinka, Sebastian
<sebastian.brzezi...@intel.com>
Subject: [PATCH] drm/i915/gt: Protect against overflow in active_engine()
>
> It is unlikely, but possible for the first call to
> intel_context_create() to fail with -ENOMEM, which would result
> in entering the following code block and decrementing "count",
> when it is set to 0 (initial condition in the for loop).
>
> Protect from overflowing the variable with additional count > 0
> check.
>
> Signed-off-by: Krzysztof Karas <krzysztof.ka...@intel.com>
> ---
> drivers/gpu/drm/i915/gt/selftest_hangcheck.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/selftest_hangcheck.c
> b/drivers/gpu/drm/i915/gt/selftest_hangcheck.c
> index f057c16410e7..cc0798dd30d5 100644
> --- a/drivers/gpu/drm/i915/gt/selftest_hangcheck.c
> +++ b/drivers/gpu/drm/i915/gt/selftest_hangcheck.c
> @@ -904,8 +904,10 @@ static void active_engine(struct kthread_work *work)
> arg->result = PTR_ERR(ce[count]);
> pr_err("[%s] Create context #%ld failed: %d!\n",
> engine->name, count, arg->result);
> - while (--count)
> - intel_context_put(ce[count]);
> + if (likely(count > 0)) {
> + while (--count)
> + intel_context_put(ce[count]);
I think it would be more streamlined to convert this into a for-loop instead of
applying the additional check separately.
E.G.:
"""
for (int i = count - 1; i >= 0; i--)
intel_context_put(ce[i]);
"""
-Jonathan Cavitt
> + }
> return;
> }
> }
> --
> 2.34.1
>
> --
> Best Regards,
> Krzysztof
>
