linux-kernel - [PATCH v3 3/3] arm64: use the correct function type for __arm64_sys_ni

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Date:   Fri, 24 May 2019 15:11:18 -0700
From:   Sami Tolvanen <samitolvanen@...gle.com>
To:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>
Cc:     Kees Cook <keescook@...omium.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Sami Tolvanen <samitolvanen@...gle.com>
Subject: [PATCH v3 3/3] arm64: use the correct function type for __arm64_sys_ni_syscall

Calling sys_ni_syscall through a syscall_fn_t pointer trips indirect
call Control-Flow Integrity checking due to a function type
mismatch. Use SYSCALL_DEFINE0 for __arm64_sys_ni_syscall instead and
remove the now unnecessary casts.

Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
---
 arch/arm64/kernel/sys.c   | 14 +++++++++-----
 arch/arm64/kernel/sys32.c |  7 ++-----
 2 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/kernel/sys.c b/arch/arm64/kernel/sys.c
index 6f91e81165147..d8b35cfe5e94e 100644
--- a/arch/arm64/kernel/sys.c
+++ b/arch/arm64/kernel/sys.c
@@ -47,22 +47,26 @@ SYSCALL_DEFINE1(arm64_personality, unsigned int, personality)
 	return ksys_personality(personality);
 }
 
+asmlinkage long sys_ni_syscall(void);
+
+asmlinkage long __arm64_sys_ni_syscall(const struct pt_regs *__unused)
+{
+	return sys_ni_syscall();
+}
+
 /*
  * Wrappers to pass the pt_regs argument.
  */
 #define sys_personality		sys_arm64_personality
 
-asmlinkage long sys_ni_syscall(const struct pt_regs *);
-#define __arm64_sys_ni_syscall	sys_ni_syscall
-
 #undef __SYSCALL
 #define __SYSCALL(nr, sym)	asmlinkage long __arm64_##sym(const struct pt_regs *);
 #include <asm/unistd.h>
 
 #undef __SYSCALL
-#define __SYSCALL(nr, sym)	[nr] = (syscall_fn_t)__arm64_##sym,
+#define __SYSCALL(nr, sym)	[nr] = __arm64_##sym,
 
 const syscall_fn_t sys_call_table[__NR_syscalls] = {
-	[0 ... __NR_syscalls - 1] = (syscall_fn_t)sys_ni_syscall,
+	[0 ... __NR_syscalls - 1] = __arm64_sys_ni_syscall,
 #include <asm/unistd.h>
 };
diff --git a/arch/arm64/kernel/sys32.c b/arch/arm64/kernel/sys32.c
index 0f8bcb7de7008..3c80a40c1c9d6 100644
--- a/arch/arm64/kernel/sys32.c
+++ b/arch/arm64/kernel/sys32.c
@@ -133,17 +133,14 @@ COMPAT_SYSCALL_DEFINE6(aarch32_fallocate, int, fd, int, mode,
 	return ksys_fallocate(fd, mode, arg_u64(offset), arg_u64(len));
 }
 
-asmlinkage long sys_ni_syscall(const struct pt_regs *);
-#define __arm64_sys_ni_syscall	sys_ni_syscall
-
 #undef __SYSCALL
 #define __SYSCALL(nr, sym)	asmlinkage long __arm64_##sym(const struct pt_regs *);
 #include <asm/unistd32.h>
 
 #undef __SYSCALL
-#define __SYSCALL(nr, sym)	[nr] = (syscall_fn_t)__arm64_##sym,
+#define __SYSCALL(nr, sym)	[nr] = __arm64_##sym,
 
 const syscall_fn_t compat_sys_call_table[__NR_compat_syscalls] = {
-	[0 ... __NR_compat_syscalls - 1] = (syscall_fn_t)sys_ni_syscall,
+	[0 ... __NR_compat_syscalls - 1] = __arm64_sys_ni_syscall,
 #include <asm/unistd32.h>
 };
-- 
2.22.0.rc1.257.g3120a18244-goog