From: Nathan Chancellor nathan@kernel.org
[ Upstream commit f37ccf8fce155d08ae2a4fb3db677911ced0c21a ]
clang's Control Flow Integrity requires that every indirect call has a valid target, which is based on the type of the function pointer. The *_show() functions in this file are written as if they will be called from dev_attr_show(); however, they will be called from sysfs_kf_seq_show() because the files were created by sysfs_create_group() and the sysfs ops are based on kobj_sysfs_ops because of kobject_add_and_create(). Because the *_show() functions do not match the type of the show() member in struct kobj_attribute, there is a CFI violation.
$ cat /sys/firmware/acpi/bgrt/{status,type,version,{x,y}offset}} 1 0 1 522 307
$ dmesg | grep "CFI failure" [ 267.761825] CFI failure (target: type_show.d5e1ad21498a5fd14edbc5c320906598.cfi_jt+0x0/0x8): [ 267.762246] CFI failure (target: xoffset_show.d5e1ad21498a5fd14edbc5c320906598.cfi_jt+0x0/0x8): [ 267.762584] CFI failure (target: status_show.d5e1ad21498a5fd14edbc5c320906598.cfi_jt+0x0/0x8): [ 267.762973] CFI failure (target: yoffset_show.d5e1ad21498a5fd14edbc5c320906598.cfi_jt+0x0/0x8): [ 267.763330] CFI failure (target: version_show.d5e1ad21498a5fd14edbc5c320906598.cfi_jt+0x0/0x8):
Convert these functions to the type of the show() member in struct kobj_attribute so that there is no more CFI violation. Because these functions are all so similar, combine them into a macro.
Fixes: d1ff4b1cdbab ("ACPI: Add support for exposing BGRT data") Link: https://github.com/ClangBuiltLinux/linux/issues/1406 Signed-off-by: Nathan Chancellor nathan@kernel.org Reviewed-by: Kees Cook keescook@chromium.org Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/acpi/bgrt.c | 57 ++++++++++++++------------------------------- 1 file changed, 18 insertions(+), 39 deletions(-)
diff --git a/drivers/acpi/bgrt.c b/drivers/acpi/bgrt.c index 19bb7f870204..e0d14017706e 100644 --- a/drivers/acpi/bgrt.c +++ b/drivers/acpi/bgrt.c @@ -15,40 +15,19 @@ static void *bgrt_image; static struct kobject *bgrt_kobj;
-static ssize_t version_show(struct device *dev, - struct device_attribute *attr, char *buf) -{ - return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab.version); -} -static DEVICE_ATTR_RO(version); - -static ssize_t status_show(struct device *dev, - struct device_attribute *attr, char *buf) -{ - return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab.status); -} -static DEVICE_ATTR_RO(status); - -static ssize_t type_show(struct device *dev, - struct device_attribute *attr, char *buf) -{ - return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab.image_type); -} -static DEVICE_ATTR_RO(type); - -static ssize_t xoffset_show(struct device *dev, - struct device_attribute *attr, char *buf) -{ - return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab.image_offset_x); -} -static DEVICE_ATTR_RO(xoffset); - -static ssize_t yoffset_show(struct device *dev, - struct device_attribute *attr, char *buf) -{ - return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab.image_offset_y); -} -static DEVICE_ATTR_RO(yoffset); +#define BGRT_SHOW(_name, _member) \ + static ssize_t _name##_show(struct kobject *kobj, \ + struct kobj_attribute *attr, char *buf) \ + { \ + return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab._member); \ + } \ + struct kobj_attribute bgrt_attr_##_name = __ATTR_RO(_name) + +BGRT_SHOW(version, version); +BGRT_SHOW(status, status); +BGRT_SHOW(type, image_type); +BGRT_SHOW(xoffset, image_offset_x); +BGRT_SHOW(yoffset, image_offset_y);
static ssize_t image_read(struct file *file, struct kobject *kobj, struct bin_attribute *attr, char *buf, loff_t off, size_t count) @@ -60,11 +39,11 @@ static ssize_t image_read(struct file *file, struct kobject *kobj, static BIN_ATTR_RO(image, 0); /* size gets filled in later */
static struct attribute *bgrt_attributes[] = { - &dev_attr_version.attr, - &dev_attr_status.attr, - &dev_attr_type.attr, - &dev_attr_xoffset.attr, - &dev_attr_yoffset.attr, + &bgrt_attr_version.attr, + &bgrt_attr_status.attr, + &bgrt_attr_type.attr, + &bgrt_attr_xoffset.attr, + &bgrt_attr_yoffset.attr, NULL, };