From 4b21d25bf519c9487935a664886956bb18f04f6d Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Mon, 24 Oct 2022 23:11:25 +0300 Subject: overflow: Introduce overflows_type() and castable_to_type() Implement a robust overflows_type() macro to test if a variable or constant value would overflow another variable or type. This can be used as a constant expression for static_assert() (which requires a constant expression[1][2]) when used on constant values. This must be constructed manually, since __builtin_add_overflow() does not produce a constant expression[3]. Additionally adds castable_to_type(), similar to __same_type(), but for checking if a constant value would overflow if cast to a given type. Add unit tests for overflows_type(), __same_type(), and castable_to_type() to the existing KUnit "overflow" test: [16:03:33] ================== overflow (21 subtests) ================== ... [16:03:33] [PASSED] overflows_type_test [16:03:33] [PASSED] same_type_test [16:03:33] [PASSED] castable_to_type_test [16:03:33] ==================== [PASSED] overflow ===================== [16:03:33] ============================================================ [16:03:33] Testing complete. Ran 21 tests: passed: 21 [16:03:33] Elapsed time: 24.022s total, 0.002s configuring, 22.598s building, 0.767s running [1] https://en.cppreference.com/w/c/language/_Static_assert [2] C11 standard (ISO/IEC 9899:2011): 6.7.10 Static assertions [3] https://gcc.gnu.org/onlinedocs/gcc/Integer-Overflow-Builtins.html 6.56 Built-in Functions to Perform Arithmetic with Overflow Checking Built-in Function: bool __builtin_add_overflow (type1 a, type2 b, Cc: Luc Van Oostenryck Cc: Nathan Chancellor Cc: Nick Desaulniers Cc: Tom Rix Cc: Daniel Latypov Cc: Vitor Massaru Iha Cc: "Gustavo A. R. Silva" Cc: Jani Nikula Cc: Mauro Carvalho Chehab Cc: linux-hardening@vger.kernel.org Cc: llvm@lists.linux.dev Co-developed-by: Gwan-gyeong Mun Signed-off-by: Gwan-gyeong Mun Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20221024201125.1416422-1-gwan-gyeong.mun@intel.com --- drivers/gpu/drm/i915/i915_user_extensions.c | 2 +- drivers/gpu/drm/i915/i915_utils.h | 4 ---- 2 files changed, 1 insertion(+), 5 deletions(-) (limited to 'drivers/gpu') diff --git a/drivers/gpu/drm/i915/i915_user_extensions.c b/drivers/gpu/drm/i915/i915_user_extensions.c index c822d0aafd2d..e3f808372c47 100644 --- a/drivers/gpu/drm/i915/i915_user_extensions.c +++ b/drivers/gpu/drm/i915/i915_user_extensions.c @@ -51,7 +51,7 @@ int i915_user_extensions(struct i915_user_extension __user *ext, return err; if (get_user(next, &ext->next_extension) || - overflows_type(next, ext)) + overflows_type(next, uintptr_t)) return -EFAULT; ext = u64_to_user_ptr(next); diff --git a/drivers/gpu/drm/i915/i915_utils.h b/drivers/gpu/drm/i915/i915_utils.h index 6c14d13364bf..67a66d4d5c70 100644 --- a/drivers/gpu/drm/i915/i915_utils.h +++ b/drivers/gpu/drm/i915/i915_utils.h @@ -111,10 +111,6 @@ bool i915_error_injected(void); #define range_overflows_end_t(type, start, size, max) \ range_overflows_end((type)(start), (type)(size), (type)(max)) -/* Note we don't consider signbits :| */ -#define overflows_type(x, T) \ - (sizeof(x) > sizeof(T) && (x) >> BITS_PER_TYPE(T)) - #define ptr_mask_bits(ptr, n) ({ \ unsigned long __v = (unsigned long)(ptr); \ (typeof(ptr))(__v & -BIT(n)); \ -- cgit v1.2.3 From 96d845a67b7e406cfed7880a724c8ca6121e022e Mon Sep 17 00:00:00 2001 From: Nathan Chancellor Date: Wed, 2 Nov 2022 08:42:15 -0700 Subject: drm/fsl-dcu: Fix return type of fsl_dcu_drm_connector_mode_valid() With clang's kernel control flow integrity (kCFI, CONFIG_CFI_CLANG), indirect call targets are validated against the expected function pointer prototype to make sure the call target is valid to help mitigate ROP attacks. If they are not identical, there is a failure at run time, which manifests as either a kernel panic or thread getting killed. A proposed warning in clang aims to catch these at compile time, which reveals: drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_rgb.c:74:16: error: incompatible function pointer types initializing 'enum drm_mode_status (*)(struct drm_connector *, struct drm_display_mode *)' with an expression of type 'int (struct drm_connector *, struct drm_display_mode *)' [-Werror,-Wincompatible-function-pointer-types-strict] .mode_valid = fsl_dcu_drm_connector_mode_valid, ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 1 error generated. ->mode_valid() in 'struct drm_connector_helper_funcs' expects a return type of 'enum drm_mode_status', not 'int'. Adjust the return type of fsl_dcu_drm_connector_mode_valid() to match the prototype's to resolve the warning and CFI failure. Link: https://github.com/ClangBuiltLinux/linux/issues/1750 Reported-by: Sami Tolvanen Signed-off-by: Nathan Chancellor Reviewed-by: Kees Cook Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20221102154215.78059-1-nathan@kernel.org --- drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_rgb.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'drivers/gpu') diff --git a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_rgb.c b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_rgb.c index 4d4a715b429d..2c2b92324a2e 100644 --- a/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_rgb.c +++ b/drivers/gpu/drm/fsl-dcu/fsl_dcu_drm_rgb.c @@ -60,8 +60,9 @@ static int fsl_dcu_drm_connector_get_modes(struct drm_connector *connector) return drm_panel_get_modes(fsl_connector->panel, connector); } -static int fsl_dcu_drm_connector_mode_valid(struct drm_connector *connector, - struct drm_display_mode *mode) +static enum drm_mode_status +fsl_dcu_drm_connector_mode_valid(struct drm_connector *connector, + struct drm_display_mode *mode) { if (mode->hdisplay & 0xf) return MODE_ERROR; -- cgit v1.2.3 From 0ad811cc08a937d875cbad0149c1bab17f84ba05 Mon Sep 17 00:00:00 2001 From: Nathan Chancellor Date: Wed, 2 Nov 2022 08:56:23 -0700 Subject: drm/sti: Fix return type of sti_{dvo,hda,hdmi}_connector_mode_valid() With clang's kernel control flow integrity (kCFI, CONFIG_CFI_CLANG), indirect call targets are validated against the expected function pointer prototype to make sure the call target is valid to help mitigate ROP attacks. If they are not identical, there is a failure at run time, which manifests as either a kernel panic or thread getting killed. A proposed warning in clang aims to catch these at compile time, which reveals: drivers/gpu/drm/sti/sti_hda.c:637:16: error: incompatible function pointer types initializing 'enum drm_mode_status (*)(struct drm_connector *, struct drm_display_mode *)' with an expression of type 'int (struct drm_connector *, struct drm_display_mode *)' [-Werror,-Wincompatible-function-pointer-types-strict] .mode_valid = sti_hda_connector_mode_valid, ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ drivers/gpu/drm/sti/sti_dvo.c:376:16: error: incompatible function pointer types initializing 'enum drm_mode_status (*)(struct drm_connector *, struct drm_display_mode *)' with an expression of type 'int (struct drm_connector *, struct drm_display_mode *)' [-Werror,-Wincompatible-function-pointer-types-strict] .mode_valid = sti_dvo_connector_mode_valid, ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ drivers/gpu/drm/sti/sti_hdmi.c:1035:16: error: incompatible function pointer types initializing 'enum drm_mode_status (*)(struct drm_connector *, struct drm_display_mode *)' with an expression of type 'int (struct drm_connector *, struct drm_display_mode *)' [-Werror,-Wincompatible-function-pointer-types-strict] .mode_valid = sti_hdmi_connector_mode_valid, ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ->mode_valid() in 'struct drm_connector_helper_funcs' expects a return type of 'enum drm_mode_status', not 'int'. Adjust the return type of sti_{dvo,hda,hdmi}_connector_mode_valid() to match the prototype's to resolve the warning and CFI failure. Link: https://github.com/ClangBuiltLinux/linux/issues/1750 Signed-off-by: Nathan Chancellor Reviewed-by: Kees Cook Signed-off-by: Kees Cook Link: https://lore.kernel.org/r/20221102155623.3042869-1-nathan@kernel.org --- drivers/gpu/drm/sti/sti_dvo.c | 5 +++-- drivers/gpu/drm/sti/sti_hda.c | 5 +++-- drivers/gpu/drm/sti/sti_hdmi.c | 5 +++-- 3 files changed, 9 insertions(+), 6 deletions(-) (limited to 'drivers/gpu') diff --git a/drivers/gpu/drm/sti/sti_dvo.c b/drivers/gpu/drm/sti/sti_dvo.c index b6ee8a82e656..076d5f30a09c 100644 --- a/drivers/gpu/drm/sti/sti_dvo.c +++ b/drivers/gpu/drm/sti/sti_dvo.c @@ -346,8 +346,9 @@ static int sti_dvo_connector_get_modes(struct drm_connector *connector) #define CLK_TOLERANCE_HZ 50 -static int sti_dvo_connector_mode_valid(struct drm_connector *connector, - struct drm_display_mode *mode) +static enum drm_mode_status +sti_dvo_connector_mode_valid(struct drm_connector *connector, + struct drm_display_mode *mode) { int target = mode->clock * 1000; int target_min = target - CLK_TOLERANCE_HZ; diff --git a/drivers/gpu/drm/sti/sti_hda.c b/drivers/gpu/drm/sti/sti_hda.c index 03cc401ed593..a53b5a15c2a9 100644 --- a/drivers/gpu/drm/sti/sti_hda.c +++ b/drivers/gpu/drm/sti/sti_hda.c @@ -601,8 +601,9 @@ static int sti_hda_connector_get_modes(struct drm_connector *connector) #define CLK_TOLERANCE_HZ 50 -static int sti_hda_connector_mode_valid(struct drm_connector *connector, - struct drm_display_mode *mode) +static enum drm_mode_status +sti_hda_connector_mode_valid(struct drm_connector *connector, + struct drm_display_mode *mode) { int target = mode->clock * 1000; int target_min = target - CLK_TOLERANCE_HZ; diff --git a/drivers/gpu/drm/sti/sti_hdmi.c b/drivers/gpu/drm/sti/sti_hdmi.c index cb82622877d2..09e0cadb6368 100644 --- a/drivers/gpu/drm/sti/sti_hdmi.c +++ b/drivers/gpu/drm/sti/sti_hdmi.c @@ -1004,8 +1004,9 @@ fail: #define CLK_TOLERANCE_HZ 50 -static int sti_hdmi_connector_mode_valid(struct drm_connector *connector, - struct drm_display_mode *mode) +static enum drm_mode_status +sti_hdmi_connector_mode_valid(struct drm_connector *connector, + struct drm_display_mode *mode) { int target = mode->clock * 1000; int target_min = target - CLK_TOLERANCE_HZ; -- cgit v1.2.3