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Subject[PATCH 4.19 47/50] arm64: compat: Dont pull syscall number from regs in arm_compat_syscall
Date
4.19-stable review patch.  If anyone has any objections, please let me know.

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

From: Will Deacon <will.deacon@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: <stable@vger.kernel.org>
Cc: Pi-Hsun Shih <pihsun@chromium.org>
Reviewed-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@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;

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