Commit 1eeb7407 authored Oct 08, 2018 by Timothy E Baldwin Committed by Greg Kroah-Hartman Nov 24, 2019

ARM: 8802/1: Call syscall_trace_exit even when system call skipped



[ Upstream commit f18aef742c8fbd68e280dff0a63ba0ca6ee8ad85 ]

On at least x86 and ARM64, and as documented in the ptrace man page
a skipped system call will still cause a syscall exit ptrace stop.

Previous to this commit 32-bit ARM did not, resulting in strace
being confused when seccomp skips system calls.

This change also impacts programs that use ptrace to skip system calls.

Fixes: ad75b514 ("ARM: 7579/1: arch/allow a scno of -1 to not cause a SIGILL")
Signed-off-by: Timothy E Baldwin <T.E.Baldwin99@members.leeds.ac.uk>
Signed-off-by: Eugene Syromyatnikov <evgsyr@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Kees Cook <keescook@chromium.org>
Tested-by: Eugene Syromyatnikov <evgsyr@gmail.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent e616dd60

arch/arm/kernel/entry-common.S

+4 −5

Original line number	Diff line number	Diff line
		@@ -296,16 +296,15 @@ __sys_trace:
		cmp scno, #-1 @ skip the syscall?
		bne 2b
		add sp, sp, #S_OFF @ restore stack
		b ret_slow_syscall

		__sys_trace_return:
		str r0, [sp, #S_R0 + S_OFF]! @ save returned r0
		__sys_trace_return_nosave:
		enable_irq_notrace
		mov r0, sp
		bl syscall_trace_exit
		b ret_slow_syscall

		__sys_trace_return_nosave:
		enable_irq_notrace
		__sys_trace_return:
		str r0, [sp, #S_R0 + S_OFF]! @ save returned r0
		mov r0, sp
		bl syscall_trace_exit
		b ret_slow_syscall