[PATCH 4.19 47/50] arm64: compat: Dont pull syscall number from regs in arm_compat_syscall

[Greg Kroah-Hartman]

4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Will Deacon <will.dea...@arm.com>

commit 53290432145a8eb143fe29e06e9c1465d43dc723 upstream.

The syscall number may have been changed by a tracer, so we should pass
the actual number in from the caller instead of pulling it from the
saved r7 value directly.

Cc: <sta...@vger.kernel.org>
Cc: Pi-Hsun Shih <pih...@chromium.org>
Reviewed-by: Dave Martin <dave.mar...@arm.com>
Signed-off-by: Will Deacon <will.dea...@arm.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>


---
 arch/arm64/kernel/sys_compat.c |    9 ++++-----
 arch/arm64/kernel/syscall.c    |    9 ++++-----
 2 files changed, 8 insertions(+), 10 deletions(-)

--- a/arch/arm64/kernel/sys_compat.c
+++ b/arch/arm64/kernel/sys_compat.c
@@ -66,12 +66,11 @@ do_compat_cache_op(unsigned long start,
 /*
  * Handle all unrecognised system calls.
  */
-long compat_arm_syscall(struct pt_regs *regs)
+long compat_arm_syscall(struct pt_regs *regs, int scno)
 {
        siginfo_t info;
-       unsigned int no = regs->regs[7];
 
-       switch (no) {
+       switch (scno) {
        /*
         * Flush a region from virtual address 'r0' to virtual address 'r1'
         * _exclusive_.  There is no alignment requirement on either address;
@@ -107,7 +106,7 @@ long compat_arm_syscall(struct pt_regs *
                 * way the calling program can gracefully determine whether
                 * a feature is supported.
                 */
-               if (no < __ARM_NR_COMPAT_END)
+               if (scno < __ARM_NR_COMPAT_END)
                        return -ENOSYS;
                break;
        }
@@ -119,6 +118,6 @@ long compat_arm_syscall(struct pt_regs *
        info.si_addr  = (void __user *)instruction_pointer(regs) -
                         (compat_thumb_mode(regs) ? 2 : 4);
 
-       arm64_notify_die("Oops - bad compat syscall(2)", regs, &info, no);
+       arm64_notify_die("Oops - bad compat syscall(2)", regs, &info, scno);
        return 0;
 }
--- a/arch/arm64/kernel/syscall.c
+++ b/arch/arm64/kernel/syscall.c
@@ -13,16 +13,15 @@
 #include <asm/thread_info.h>
 #include <asm/unistd.h>
 
-long compat_arm_syscall(struct pt_regs *regs);
-
+long compat_arm_syscall(struct pt_regs *regs, int scno);
 long sys_ni_syscall(void);
 
-asmlinkage long do_ni_syscall(struct pt_regs *regs)
+static long do_ni_syscall(struct pt_regs *regs, int scno)
 {
 #ifdef CONFIG_COMPAT
        long ret;
        if (is_compat_task()) {
-               ret = compat_arm_syscall(regs);
+               ret = compat_arm_syscall(regs, scno);
                if (ret != -ENOSYS)
                        return ret;
        }
@@ -47,7 +46,7 @@ static void invoke_syscall(struct pt_reg
                syscall_fn = syscall_table[array_index_nospec(scno, sc_nr)];
                ret = __invoke_syscall(regs, syscall_fn);
        } else {
-               ret = do_ni_syscall(regs);
+               ret = do_ni_syscall(regs, scno);
        }
 
        regs->regs[0] = ret;