[PATCH 5.4 050/203] syscalls/x86: Fix function types in COND_SYSCALL

Greg Kroah-Hartman
2020-01-16T23:46:45Z

From: Sami Tolvanen <samitolvanen@google.com>

commit 6e4847640c6aebcaa2d9b3686cecc91b41f09269 upstream.

Define a weak function in COND_SYSCALL instead of a weak alias to
sys_ni_syscall(), which has an incompatible type. This fixes indirect
call mismatches with Control-Flow Integrity (CFI) checking.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Acked-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H . Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20191008224049.115427-6-samitolvanen@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/include/asm/syscall_wrapper.h | 21 ++++++++++++++++-----
1 file changed, 16 insertions(+), 5 deletions(-)

--- a/arch/x86/include/asm/syscall_wrapper.h
+++ b/arch/x86/include/asm/syscall_wrapper.h
@@ -6,6 +6,8 @@
#ifndef _ASM_X86_SYSCALL_WRAPPER_H
#define _ASM_X86_SYSCALL_WRAPPER_H

+struct pt_regs;
+
/* Mapping of registers to parameters for syscalls on x86-64 and x32 */
#define SC_X86_64_REGS_TO_ARGS(x, ...) \
__MAP(x,__SC_ARGS \
@@ -64,9 +66,15 @@
SYSCALL_ALIAS(__ia32_sys_##sname, __x64_sys_##sname); \
asmlinkage long __x64_sys_##sname(const struct pt_regs *__unused)

-#define COND_SYSCALL(name) \
- cond_syscall(__x64_sys_##name); \
- cond_syscall(__ia32_sys_##name)
+#define COND_SYSCALL(name) \
+ asmlinkage __weak long __x64_sys_##name(const struct pt_regs *__unused) \
+ { \
+ return sys_ni_syscall(); \
+ } \
+ asmlinkage __weak long __ia32_sys_##name(const struct pt_regs *__unused)\
+ { \
+ return sys_ni_syscall(); \
+ }

#define SYS_NI(name) \
SYSCALL_ALIAS(__x64_sys_##name, sys_ni_posix_timers); \
@@ -218,7 +226,11 @@
#endif

#ifndef COND_SYSCALL
-#define COND_SYSCALL(name) cond_syscall(__x64_sys_##name)
+#define COND_SYSCALL(name) \
+ asmlinkage __weak long __x64_sys_##name(const struct pt_regs *__unused) \
+ { \
+ return sys_ni_syscall(); \
+ }
#endif

#ifndef SYS_NI
@@ -230,7 +242,6 @@
* For VSYSCALLS, we need to declare these three syscalls with the new
* pt_regs-based calling convention for in-kernel use.
*/
-struct pt_regs;
asmlinkage long __x64_sys_getcpu(const struct pt_regs *regs);
asmlinkage long __x64_sys_gettimeofday(const struct pt_regs *regs);
asmlinkage long __x64_sys_time(const struct pt_regs *regs);