linux-hardening - [PATCH][next] drm/nouveau: svm: Avoid -Wflex-array-member-not-at-end warning

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Message-ID: <Z-2uezeHt1aaHH6x@kspp>
Date: Wed, 2 Apr 2025 15:39:07 -0600
From: "Gustavo A. R. Silva" <gustavoars@...nel.org>
To: Lyude Paul <lyude@...hat.com>, Danilo Krummrich <dakr@...nel.org>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>
Cc: dri-devel@...ts.freedesktop.org, nouveau@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	linux-hardening@...r.kernel.org
Subject: [PATCH][next] drm/nouveau: svm: Avoid -Wflex-array-member-not-at-end
 warning

-Wflex-array-member-not-at-end was introduced in GCC-14, and we are
getting ready to enable it, globally.

Use the `DEFINE_RAW_FLEX()` helper for an on-stack definition of
a flexible structure where the size of the flexible-array member
is known at compile-time, and refactor the rest of the code,
accordingly.

So, with these changes, fix the following warning:

drivers/gpu/drm/nouveau/nouveau_svm.c:724:44: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]

Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
 drivers/gpu/drm/nouveau/nouveau_svm.c | 39 +++++++++++++--------------
 1 file changed, 18 insertions(+), 21 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_svm.c b/drivers/gpu/drm/nouveau/nouveau_svm.c
index e12e2596ed84..6fa387da0637 100644
--- a/drivers/gpu/drm/nouveau/nouveau_svm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_svm.c
@@ -720,10 +720,7 @@ nouveau_svm_fault(struct work_struct *work)
 	struct nouveau_svm *svm = container_of(buffer, typeof(*svm), buffer[buffer->id]);
 	struct nvif_object *device = &svm->drm->client.device.object;
 	struct nouveau_svmm *svmm;
-	struct {
-		struct nouveau_pfnmap_args i;
-		u64 phys[1];
-	} args;
+	DEFINE_RAW_FLEX(struct nouveau_pfnmap_args, args, p.phys, 1);
 	unsigned long hmm_flags;
 	u64 inst, start, limit;
 	int fi, fn;
@@ -772,11 +769,11 @@ nouveau_svm_fault(struct work_struct *work)
 	mutex_unlock(&svm->mutex);
 
 	/* Process list of faults. */
-	args.i.i.version = 0;
-	args.i.i.type = NVIF_IOCTL_V0_MTHD;
-	args.i.m.version = 0;
-	args.i.m.method = NVIF_VMM_V0_PFNMAP;
-	args.i.p.version = 0;
+	args->i.version = 0;
+	args->i.type = NVIF_IOCTL_V0_MTHD;
+	args->m.version = 0;
+	args->m.method = NVIF_VMM_V0_PFNMAP;
+	args->p.version = 0;
 
 	for (fi = 0; fn = fi + 1, fi < buffer->fault_nr; fi = fn) {
 		struct svm_notifier notifier;
@@ -802,9 +799,9 @@ nouveau_svm_fault(struct work_struct *work)
 		 * fault window, determining required pages and access
 		 * permissions based on pending faults.
 		 */
-		args.i.p.addr = start;
-		args.i.p.page = PAGE_SHIFT;
-		args.i.p.size = PAGE_SIZE;
+		args->p.addr = start;
+		args->p.page = PAGE_SHIFT;
+		args->p.size = PAGE_SIZE;
 		/*
 		 * Determine required permissions based on GPU fault
 		 * access flags.
@@ -832,16 +829,16 @@ nouveau_svm_fault(struct work_struct *work)
 
 		notifier.svmm = svmm;
 		if (atomic)
-			ret = nouveau_atomic_range_fault(svmm, svm->drm,
-							 &args.i, sizeof(args),
+			ret = nouveau_atomic_range_fault(svmm, svm->drm, args,
+							 __struct_size(args),
 							 &notifier);
 		else
-			ret = nouveau_range_fault(svmm, svm->drm, &args.i,
-						  sizeof(args), hmm_flags,
-						  &notifier);
+			ret = nouveau_range_fault(svmm, svm->drm, args,
+						  __struct_size(args),
+						  hmm_flags, &notifier);
 		mmput(mm);
 
-		limit = args.i.p.addr + args.i.p.size;
+		limit = args->p.addr + args->p.size;
 		for (fn = fi; ++fn < buffer->fault_nr; ) {
 			/* It's okay to skip over duplicate addresses from the
 			 * same SVMM as faults are ordered by access type such
@@ -855,14 +852,14 @@ nouveau_svm_fault(struct work_struct *work)
 			if (buffer->fault[fn]->svmm != svmm ||
 			    buffer->fault[fn]->addr >= limit ||
 			    (buffer->fault[fi]->access == FAULT_ACCESS_READ &&
-			     !(args.phys[0] & NVIF_VMM_PFNMAP_V0_V)) ||
+			     !(args->p.phys[0] & NVIF_VMM_PFNMAP_V0_V)) ||
 			    (buffer->fault[fi]->access != FAULT_ACCESS_READ &&
 			     buffer->fault[fi]->access != FAULT_ACCESS_PREFETCH &&
-			     !(args.phys[0] & NVIF_VMM_PFNMAP_V0_W)) ||
+			     !(args->p.phys[0] & NVIF_VMM_PFNMAP_V0_W)) ||
 			    (buffer->fault[fi]->access != FAULT_ACCESS_READ &&
 			     buffer->fault[fi]->access != FAULT_ACCESS_WRITE &&
 			     buffer->fault[fi]->access != FAULT_ACCESS_PREFETCH &&
-			     !(args.phys[0] & NVIF_VMM_PFNMAP_V0_A)))
+			     !(args->p.phys[0] & NVIF_VMM_PFNMAP_V0_A)))
 				break;
 		}
 
-- 
2.43.0