From: Nathan Chancellor nathan@kernel.org
commit fca41af18e10318e4de090db47d9fa7169e1bf2f upstream.
fw_cfg_showrev() is called by an indirect call in kobj_attr_show(), which violates clang's CFI checking because fw_cfg_showrev()'s second parameter is 'struct attribute', whereas the ->show() member of 'struct kobj_structure' expects the second parameter to be of type 'struct kobj_attribute'.
$ cat /sys/firmware/qemu_fw_cfg/rev 3
$ dmesg | grep "CFI failure" [ 26.016832] CFI failure (target: fw_cfg_showrev+0x0/0x8):
Fix this by converting fw_cfg_rev_attr to 'struct kobj_attribute' where this would have been caught automatically by the incompatible pointer types compiler warning. Update fw_cfg_showrev() accordingly.
Fixes: 75f3e8e47f38 ("firmware: introduce sysfs driver for QEMU's fw_cfg device") Link: https://github.com/ClangBuiltLinux/linux/issues/1299 Signed-off-by: Nathan Chancellor nathan@kernel.org Reviewed-by: Sami Tolvanen samitolvanen@google.com Tested-by: Sedat Dilek sedat.dilek@gmail.com Reviewed-by: Sami Tolvanen samitolvanen@google.com Reviewed-by: Philippe Mathieu-Daudé philmd@redhat.com Signed-off-by: Kees Cook keescook@chromium.org Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20210211194258.4137998-1-nathan@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/firmware/qemu_fw_cfg.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-)
--- a/drivers/firmware/qemu_fw_cfg.c +++ b/drivers/firmware/qemu_fw_cfg.c @@ -192,15 +192,13 @@ static int fw_cfg_do_platform_probe(stru /* fw_cfg revision attribute, in /sys/firmware/qemu_fw_cfg top-level dir. */ static u32 fw_cfg_rev;
-static ssize_t fw_cfg_showrev(struct kobject *k, struct attribute *a, char *buf) +static ssize_t fw_cfg_showrev(struct kobject *k, struct kobj_attribute *a, + char *buf) { return sprintf(buf, "%u\n", fw_cfg_rev); }
-static const struct { - struct attribute attr; - ssize_t (*show)(struct kobject *k, struct attribute *a, char *buf); -} fw_cfg_rev_attr = { +static const struct kobj_attribute fw_cfg_rev_attr = { .attr = { .name = "rev", .mode = S_IRUSR }, .show = fw_cfg_showrev, };