The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 53290432145a8eb143fe29e06e9c1465d43dc723 Mon Sep 17 00:00:00 2001

From: Will Deacon will.deacon@arm.com Date: Thu, 3 Jan 2019 18:00:39 +0000 Subject: [PATCH] arm64: compat: Don't pull syscall number from regs in arm_compat_syscall

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

diff --git a/arch/arm64/kernel/sys_compat.c b/arch/arm64/kernel/sys_compat.c index a79db4e485a6..bc348ab3dd6b 100644 --- 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, unsigned long end, int flags) /* * Handle all unrecognised system calls. */ -long compat_arm_syscall(struct pt_regs *regs) +long compat_arm_syscall(struct pt_regs *regs, int scno) { - unsigned int no = regs->regs[7]; void __user *addr;

- 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 *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; } @@ -116,6 +115,6 @@ long compat_arm_syscall(struct pt_regs *regs) (compat_thumb_mode(regs) ? 2 : 4);

arm64_notify_die("Oops - bad compat syscall(2)", regs, - SIGILL, ILL_ILLTRP, addr, no); + SIGILL, ILL_ILLTRP, addr, scno); return 0; } diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c index 032d22312881..5610ac01c1ec 100644 --- 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_regs *regs, unsigned int scno, 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;