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R. Silva" , Bill Wendling , Justin Stitt , linux-kernel@vger.kernel.org Subject: [PATCH 49/82] drm/i915: Refactor intentional wrap-around test Date: Mon, 22 Jan 2024 16:27:24 -0800 Message-Id: <20240123002814.1396804-49-keescook@chromium.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240122235208.work.748-kees@kernel.org> References: <20240122235208.work.748-kees@kernel.org> Precedence: bulk X-Mailing-List: linux-hardening@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2342; i=keescook@chromium.org; h=from:subject; bh=oiG+TsWcxpCmRd1+V7WC6Rzkst0Tmp3FWPUBfyk7tD0=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBlrwgJM8j5gj77tQNAWNgLrGW9Rf152U5LzsLsJ LLY7jY3zQCJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCZa8ICQAKCRCJcvTf3G3A JlTyD/9tInsgMQJNhzXLV4lkjEdwrZuxy10l8+2Dh6eeSAQbaL+DgNMujkfU/ewIc6vsc6zeZLn 3ACm3O16LQN/0j5S0RYKIeVgjfXSZAYGJuwYmW3jBM3o8s9hNPi/SXXGp0toQyaZ73L3hcRB4AO 2C01S7JnD87/2LBgN5VfyCDAUOfgYSqdE4ibXD+3+uyUSrbM8B+GimE4cH4ORUxm7YMLto9zpu+ oxqd7qMyF6AyMavkv5ySlinqmiOVJ83f+YZ+oRowh0q5fTfSibio56QvEqpQZCtefn09GEz+IoC Tnb8E/IS3JJOLLdskrUiX3bNAd51XjStK5+qpc0F35indv1uLzV53YFhU5912hmIDcxwPmmtHTi OXiRWa2TWfKEgQKSVyJmGL9esA3rmPtERr7goeI8/nFMWEb4Qy+cpevxG1qft33h0Z7enHXDTBT JHJYXrmewrWmRrBpNFH54MHVPInL6YqLuU56FYnU3go2zz3tsoo8VutSaww+foZj6VUcti/X6fF PHZBFPajfhvY94xWQMXnk+iHmY7GJNwyVxOdnF8YsTZv23cXzWc9GXdAMMp6lw4By2hz73i3BNZ JSnAMxGSHmwnz/DNjaVSvjUSE5b/U82hIxtLLj6mKkDb5Osg8f47u2KWYVVd868CRAaVvfeVUVJ 1IBIdYvVvwQ4wvw== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 In an effort to separate intentional arithmetic wrap-around from unexpected wrap-around, we need to refactor places that depend on this kind of math. One of the most common code patterns of this is: VAR + value < VAR Notably, this is considered "undefined behavior" for signed and pointer types, which the kernel works around by using the -fno-strict-overflow option in the build[1] (which used to just be -fwrapv). Regardless, we want to get the kernel source to the position where we can meaningfully instrument arithmetic wrap-around conditions and catch them when they are unexpected, regardless of whether they are signed[2], unsigned[3], or pointer[4] types. Refactor open-coded wrap-around addition test to use add_would_overflow(). This paves the way to enabling the wrap-around sanitizers in the future. Link: https://git.kernel.org/linus/68df3755e383e6fecf2354a67b08f92f18536594 [1] Link: https://github.com/KSPP/linux/issues/26 [2] Link: https://github.com/KSPP/linux/issues/27 [3] Link: https://github.com/KSPP/linux/issues/344 [4] Cc: Maarten Lankhorst Cc: Maxime Ripard Cc: Thomas Zimmermann Cc: Jani Nikula Cc: Joonas Lahtinen Cc: Rodrigo Vivi Cc: Tvrtko Ursulin Cc: David Airlie Cc: Daniel Vetter Cc: intel-gfx@lists.freedesktop.org Cc: dri-devel@lists.freedesktop.org Signed-off-by: Kees Cook --- drivers/gpu/drm/i915/i915_vma.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c index d09aad34ba37..1a4f048a5df9 100644 --- a/drivers/gpu/drm/i915/i915_vma.c +++ b/drivers/gpu/drm/i915/i915_vma.c @@ -1535,7 +1535,7 @@ int i915_vma_pin_ww(struct i915_vma *vma, struct i915_gem_ww_ctx *ww, goto err_remove; /* There should only be at most 2 active bindings (user, global) */ - GEM_BUG_ON(bound + I915_VMA_PAGES_ACTIVE < bound); + GEM_BUG_ON(add_would_overflow(bound, I915_VMA_PAGES_ACTIVE)); atomic_add(I915_VMA_PAGES_ACTIVE, &vma->pages_count); list_move_tail(&vma->vm_link, &vma->vm->bound_list);