From mboxrd@z Thu Jan 1 00:00:00 1970 From: ldv@altlinux.org (Dmitry V. Levin) Date: Wed, 14 Mar 2018 02:58:50 +0300 Subject: ARM: Call syscall_trace_exit even when system call skipped In-Reply-To: <20180203152112.2449-1-T.E.Baldwin99@members.leeds.ac.uk> References: <20180203152112.2449-1-T.E.Baldwin99@members.leeds.ac.uk> Message-ID: <20180313235850.GA18373@altlinux.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Kees, As you probably know, ptracing of processes affected by SECCOMP_RET_TRAP is broken on ARM since your commit v3.7-rc1-11-gad75b51459ae. Could you review the proposed fix, please? P.S. There is a test for this kernel bug in strace test suite, you might find it useful: https://github.com/strace/strace/compare/ldv/SECCOMP_RET_TRAP On Sat, Feb 03, 2018 at 03:21:12PM +0000, Timothy E Baldwin wrote: > 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 > --- > 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 99c908226065..88a65157307d 100644 > --- a/arch/arm/kernel/entry-common.S > +++ b/arch/arm/kernel/entry-common.S > @@ -288,16 +288,15 @@ __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 -- ldv -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 801 bytes Desc: not available URL: