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From: Andi Shyti <andi.shyti@kernel.org>
To: Sebastian Brzezinka <sebastian.brzezinka@intel.com>
Cc: dri-devel@lists.freedesktop.org,
	maarten.lankhorst@linux.intel.com,  andi.shyti@linux.intel.com,
	krzysztof.karas@intel.com, krzysztof.niemiec@intel.com,
	intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH] drm/fb-helper: guard against NULL fb_helper->funcs in restore path
Date: Thu, 23 Jul 2026 11:27:51 +0200	[thread overview]
Message-ID: <amHed5UASdD_3Foc@zenone.zhora.eu> (raw)
In-Reply-To: <e1957da52fcdd1d88a285553d36e12a0362a8258.1784196681.git.sebastian.brzezinka@intel.com>

Hi Sebastian,

On Thu, Jul 16, 2026 at 12:14:33PM +0200, Sebastian Brzezinka wrote:
> When a driver's fbdev probe callback fails before assigning
> fb_helper->funcs (e.g. i915's intel_fbdev_driver_fbdev_probe() bailing
> out early on a DMA/GGTT pin failure), the fbdev client stays registered
> with fb_helper->funcs == NULL. Any later restore, such as on drm fd close
> via drm_client_dev_restore() -> drm_fbdev_client_restore(), reaches
> __drm_fb_helper_restore_fbdev_mode_unlocked() and unconditionally
> dereferences fb_helper->funcs->fb_restore, causing a NULL pointer
> dereference.
> 
> Guard the fb_restore call with a NULL check on fb_helper->funcs.
> 
> Fixes: 2ef5754c9649 ("drm/i915/display: fbdev: Move custom restore code to new callback")
> Signed-off-by: Sebastian Brzezinka <sebastian.brzezinka@intel.com>

Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>

Thanks,
Andi

      parent reply	other threads:[~2026-07-23  9:28 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-07-16 10:14 [PATCH] drm/fb-helper: guard against NULL fb_helper->funcs in restore path Sebastian Brzezinka
2026-07-16 11:13 ` ✓ i915.CI.BAT: success for " Patchwork
2026-07-16 16:07 ` ✗ i915.CI.Full: failure " Patchwork
2026-07-20  7:35 ` [PATCH] " Krzysztof Karas
2026-07-20 19:33 ` ✓ i915.CI.BAT: success for drm/fb-helper: guard against NULL fb_helper->funcs in restore path (rev2) Patchwork
2026-07-21  2:28 ` ✓ i915.CI.Full: " Patchwork
2026-07-23  9:27 ` Andi Shyti [this message]

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