From: Timothy E Baldwin T.E.Baldwin99@members.leeds.ac.uk
[ 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: ad75b51459ae ("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 --- arch/arm/kernel/entry-common.S | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S index d69adfb3d79e6..178a2a9606595 100644 --- a/arch/arm/kernel/entry-common.S +++ b/arch/arm/kernel/entry-common.S @@ -263,16 +263,15 @@ __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