Messages in this thread | | | Date | Sat, 4 Jul 2020 13:33:56 +0100 | From | Will Deacon <> | Subject | Re: ptrace: seccomp: Return value when the call was already invalid |
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On Fri, Jul 03, 2020 at 08:52:05AM -0700, Kees Cook wrote: > On Fri, Jul 03, 2020 at 04:44:27PM +0100, Will Deacon wrote: > > On Fri, Jul 03, 2020 at 08:17:19AM -0700, Kees Cook wrote: > > > On Fri, Jul 03, 2020 at 09:39:14AM +0100, Will Deacon wrote: > > > > diff --git a/arch/arm64/kernel/syscall.c b/arch/arm64/kernel/syscall.c > > > > index 5f5b868292f5..a13661f44818 100644 > > > > --- a/arch/arm64/kernel/syscall.c > > > > +++ b/arch/arm64/kernel/syscall.c > > > > @@ -121,12 +121,10 @@ static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr, > > > > user_exit(); > > > > > > > > if (has_syscall_work(flags)) { > > > > - /* set default errno for user-issued syscall(-1) */ > > > > - if (scno == NO_SYSCALL) > > > > - regs->regs[0] = -ENOSYS; > > > > - scno = syscall_trace_enter(regs); > > > > - if (scno == NO_SYSCALL) > > > > + if (syscall_trace_enter(regs)) > > > > goto trace_exit; > > > > + > > > > + scno = regs->syscallno; > > > > } > > > > > > > > invoke_syscall(regs, scno, sc_nr, syscall_table); > > > > > > What effect do either of these patches have on the existing seccomp > > > selftests: tools/testing/selftests/seccomp/seccomp_bpf ? > > > > Tests! Thanks, I'll have a look. > > Thanks! > > (And either way, that this behavioral difference went unnoticed means we > need to add a test to the selftests for this patch.)
Unsurprisingly, I don't think the tests go near this. I get 75/77 passes on arm64 defconfig with or without these changes.
We could add a test, but then we'd have to agree on what it's supposed to be doing ;)
Will
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