On Thu, Jan 03, 2019 at 06:13:59PM +0000, Will Deacon wrote:
> 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.
Reviewed-by: Dave Martin <Dave.Martin@xxxxxxx>
I was confused by the history here: commit 4141c857fd09 ("arm64: convert
raw syscall invocation to C") breaks syscall changing via
discarding the return from syscall_trace_enter() (which would also break
this case for compat), but the subsequent patch that migrates the
syscall code to C appears to fix it again.
>
> Cc: <stable@xxxxxxxxxxxxxxx>
> Cc: Dave Martin <Dave.Martin@xxxxxxx>
> Cc: Pi-Hsun Shih <pihsun@xxxxxxxxxxxx>
> Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
> ---
> arch/arm64/kernel/sys_compat.c | 9 ++++-----
> arch/arm64/kernel/syscall.c | 9 ++++-----
> 2 files changed, 8 insertions(+), 10 deletions(-)
>
> diff --git a/arch/arm64/kernel/sys_compat.c b/arch/arm64/kernel/sys_compat.c
> index 5972b7533fa0..54c29cd38ff9 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_syscall_end)
> + if (scno < __ARM_NR_compat_syscall_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;
> --
> 2.1.4
>
>
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