linux-kernel - RE: [RFC PATCH] drm/i915: i915 null pointer dereference

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Message-ID: <DM3PPF208195D8D5D24B6BA0387168AD2FDE39BA@DM3PPF208195D8D.namprd11.prod.outlook.com>
Date: Tue, 3 Feb 2026 04:40:43 +0000
From: "Kandpal, Suraj" <suraj.kandpal@...el.com>
To: Rahul Bukte <rahul.bukte@...y.com>, "intel-gfx@...ts.freedesktop.org"
	<intel-gfx@...ts.freedesktop.org>, "dri-devel@...ts.freedesktop.org"
	<dri-devel@...ts.freedesktop.org>, "jani.nikula@...ux.intel.com"
	<jani.nikula@...ux.intel.com>, "joonas.lahtinen@...ux.intel.com"
	<joonas.lahtinen@...ux.intel.com>, "Vivi, Rodrigo" <rodrigo.vivi@...el.com>,
	"tursulin@...ulin.net" <tursulin@...ulin.net>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"daniel.palmer@...y.com" <daniel.palmer@...y.com>
Subject: RE: [RFC PATCH] drm/i915: i915 null pointer dereference

> Subject: [RFC PATCH] drm/i915: i915 null pointer dereference

You can remove the RFC patch this patch LGTM from a solution standpoint.
You need to modify the subject to drm/i915/gt : Check set_default_submission() before deferencing it.
Ill be resending this patch to get results from LGCI. After which this can be merged.

Otherwise this LGTM,
Reviewed-by: Suraj Kandpal <suraj.kandpal@...el.com>


> 
> When the i915 driver firmware binaries are not present, the
> set_default_submission pointer is not set. This pointer is dereferenced during
> suspend anyways.
> 
> Add a check to make sure it is set before dereferencing.
> 
> # echo +20 > /sys/class/rtc/rtc0/wakealarm && echo mem >
> /sys/power/state
> [   23.289926] PM: suspend entry (deep)
> [   23.293558] Filesystems sync: 0.000 seconds
> [   23.298010] Freezing user space processes
> [   23.302771] Freezing user space processes completed (elapsed 0.000
> seconds)
> [   23.309766] OOM killer disabled.
> [   23.313027] Freezing remaining freezable tasks
> [   23.318540] Freezing remaining freezable tasks completed (elapsed 0.001
> seconds)
> [   23.342038] serial 00:05: disabled
> [   23.345719] serial 00:02: disabled
> [   23.349342] serial 00:01: disabled
> [   23.353782] sd 0:0:0:0: [sda] Synchronizing SCSI cache
> [   23.358993] sd 1:0:0:0: [sdb] Synchronizing SCSI cache
> [   23.361635] ata1.00: Entering standby power mode
> [   23.368863] ata2.00: Entering standby power mode
> [   23.445187] BUG: kernel NULL pointer dereference, address:
> 0000000000000000
> [   23.452194] #PF: supervisor instruction fetch in kernel mode
> [   23.457896] #PF: error_code(0x0010) - not-present page
> [   23.463065] PGD 0 P4D 0
> [   23.465640] Oops: Oops: 0010 [#1] SMP NOPTI
> [   23.469869] CPU: 8 UID: 0 PID: 211 Comm: kworker/u48:18 Tainted: G S
> W           6.19.0-rc4-00020-gf0b9d8eb98df #10 PREEMPT(voluntary)
> [   23.482512] Tainted: [S]=CPU_OUT_OF_SPEC, [W]=WARN
> [   23.496511] Workqueue: async async_run_entry_fn
> [   23.501087] RIP: 0010:0x0
> [   23.503755] Code: Unable to access opcode bytes at 0xffffffffffffffd6.
> [   23.510324] RSP: 0018:ffffb4a60065fca8 EFLAGS: 00010246
> [   23.515592] RAX: 0000000000000000 RBX: ffff9f428290e000 RCX:
> 000000000000000f
> [   23.522765] RDX: 0000000000000000 RSI: 0000000000000282 RDI:
> ffff9f428290e000
> [   23.529937] RBP: ffff9f4282907070 R08: ffff9f4281130428 R09:
> 00000000ffffffff
> [   23.537111] R10: 0000000000000000 R11: 0000000000000001 R12:
> ffff9f42829070f8
> [   23.544284] R13: ffff9f4282906028 R14: ffff9f4282900000 R15:
> ffff9f4282906b68
> [   23.551457] FS:  0000000000000000(0000) GS:ffff9f466b2cf000(0000)
> knlGS:0000000000000000
> [   23.559588] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [   23.565365] CR2: ffffffffffffffd6 CR3: 000000031c230001 CR4:
> 0000000000f70ef0
> [   23.572539] PKRU: 55555554
> [   23.575281] Call Trace:
> [   23.577770]  <TASK>
> [   23.579905]  intel_engines_reset_default_submission+0x42/0x60
> [   23.585695]  __intel_gt_unset_wedged+0x191/0x200
> [   23.590360]  intel_gt_unset_wedged+0x20/0x40
> [   23.594675]  gt_sanitize+0x15e/0x170
> [   23.598290]  i915_gem_suspend_late+0x6b/0x180
> [   23.602692]  i915_drm_suspend_late+0x35/0xf0
> [   23.607008]  ? __pfx_pci_pm_suspend_late+0x10/0x10
> [   23.611843]  dpm_run_callback+0x78/0x1c0
> [   23.615817]  device_suspend_late+0xde/0x2e0
> [   23.620037]  async_suspend_late+0x18/0x30
> [   23.624082]  async_run_entry_fn+0x25/0xa0
> [   23.628129]  process_one_work+0x15b/0x380
> [   23.632182]  worker_thread+0x2a5/0x3c0
> [   23.635973]  ? __pfx_worker_thread+0x10/0x10
> [   23.640279]  kthread+0xf6/0x1f0
> [   23.643464]  ? __pfx_kthread+0x10/0x10
> [   23.647263]  ? __pfx_kthread+0x10/0x10
> [   23.651045]  ret_from_fork+0x131/0x190
> [   23.654837]  ? __pfx_kthread+0x10/0x10
> [   23.658634]  ret_from_fork_asm+0x1a/0x30
> [   23.662597]  </TASK>
> [   23.664826] Modules linked in:
> [   23.667914] CR2: 0000000000000000
> [   23.671271] ------------[ cut here ]------------
> 
> Signed-off-by: Rahul Bukte <rahul.bukte@...y.com>
> ---
>  drivers/gpu/drm/i915/gt/intel_engine_cs.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> index b721bbd23356..ce8cdd517daa 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
> @@ -1969,7 +1969,8 @@ void
> intel_engines_reset_default_submission(struct intel_gt *gt)
>  		if (engine->sanitize)
>  			engine->sanitize(engine);
> 
> -		engine->set_default_submission(engine);
> +		if (engine->set_default_submission)
> +			engine->set_default_submission(engine);
>  	}
>  }
> 
> --
> 2.43.0