ARM: Call syscall_trace_exit even when system call skipped
From: Kees Cook <hidden>
Date: 2018-10-08 18:08:16
On Mon, Oct 8, 2018 at 4:00 AM, Eugene Syromyatnikov [off-list ref] wrote:
From: Timothy E Baldwin <redacted>
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: ad75b51459ae ("ARM: 7579/1: arch/allow a scno of -1 to not cause a SIGILL")
Signed-off-by: Timothy E Baldwin <redacted>
Signed-off-by: Eugene Syromyatnikov <redacted>
Reviewed-by: Kees Cook <redacted>
Tested-by: Kees Cook <redacted>
Tested-by: Eugene Syromyatnikov <redacted>
---
KernelVersion: 4.19-rc7Did this actually make it into the patch tracker? I don't see it in Incoming... -Kees
quoted hunk ↗ jump to hunk
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S index 746565a..0465d65 100644 --- a/arch/arm/kernel/entry-common.S +++ b/arch/arm/kernel/entry-common.S@@ -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 --2.1.4
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