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Wed, 08 Apr 2026 15:49:44 -0700 (PDT) Received: from DESKTOP-K4142FH.localdomain ([197.146.147.164]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43d1e4d2738sm63318408f8f.24.2026.04.08.15.49.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 08 Apr 2026 15:49:44 -0700 (PDT) From: Yassine Mounir To: joonas.lahtinen@linux.intel.com Cc: ville.syrjala@linux.intel.com, torvalds@linuxfoundation.org, intel-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org, Yassine Mounir Subject: [PATCH v4] drm/i915/gem: Fix relocation race and simplify VMA lookup Date: Wed, 8 Apr 2026 23:49:05 +0100 Message-ID: <20260408224905.5918-1-sosohero200@gmail.com> X-Mailer: git-send-email 2.51.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Pin the object lifetime in eb_relocate_vma() using i915_gem_object_get() and i915_gem_object_put() to prevent a Use-After-Free (UAF) if the handle is closed concurrently during relocation. Additionally, simplify eb_lookup_vma() by removing the redundant vma->vm =3D=3D vm check. As noted by Joonas, this check is unnecessary since commit d4433c7600f7. Removing it also avoids the "insane" logic of returning a VMA without a reference, satisfying the sanity requirements requested by Linus. Fixes: d4433c7600f7 ("drm/i915: Multi-vm support") Suggested-by: Ville Syrj=C3=A4l=C3=A4 Suggested-by: Joonas Lahtinen Signed-off-by: Yassine Mounir --- drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/d= rm/i915/gem/i915_gem_execbuffer.c index 942f4eed8..50eeb4771 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c @@ -896,10 +896,8 @@ static struct i915_vma *eb_lookup_vma(struct i915_exec= buffer *eb, u32 handle) =20 rcu_read_lock(); vma =3D radix_tree_lookup(&eb->gem_context->handles_vma, handle); - if (likely(vma && vma->vm =3D=3D vm)) + if (likely(vma)) vma =3D i915_vma_tryget(vma); - else - vma =3D NULL; rcu_read_unlock(); if (likely(vma)) return vma; @@ -1529,7 +1527,7 @@ static int eb_relocate_vma(struct i915_execbuffer *eb= , struct eb_vma *ev) */ if (unlikely(!access_ok(urelocs, remain * sizeof(*urelocs)))) return -EFAULT; - + i915_gem_object_get(ev->vma->obj); do { struct drm_i915_gem_relocation_entry *r =3D stack; unsigned int count =3D @@ -1590,6 +1588,7 @@ static int eb_relocate_vma(struct i915_execbuffer *eb= , struct eb_vma *ev) urelocs +=3D ARRAY_SIZE(stack); } while (remain); out: + i915_gem_object_put(ev->vma->obj); reloc_cache_reset(&eb->reloc_cache, eb); return remain; } --=20 2.51.0