On Fri, Aug 28, 2020 at 06:38:09PM +0200, John Paul Adrian Glaubitz wrote:
> Hi!
>
> On 8/28/20 6:30 PM, Rich Felker wrote:
> > I'm about to test a patch along these lines and will report what I
> > find.
>
> Let me know when you have something to test and I will test the patch as
> well, making sure we're not breaking seccomp again.
If you have a seccomp test setup, please try the following patch. I'm
not sure if the end result is entirely correct, but I believe it's
at least much closer to correct than the code was before or after
adding SECCOMP_FILTER.
diff --git a/arch/sh/kernel/entry-common.S b/arch/sh/kernel/entry-common.S
index ad963104d22d..0560a8054215 100644
--- a/arch/sh/kernel/entry-common.S
+++ b/arch/sh/kernel/entry-common.S
@@ -368,9 +368,6 @@ syscall_trace_entry:
mov.l 7f, r11 ! Call do_syscall_trace_enter which notifies
jsr @r11 ! superior (will chomp R[0-7])
nop
- cmp/eq #-1, r0
- bt syscall_exit
- mov.l r0, @(OFF_R0,r15) ! Save return value
! Reload R0-R4 from kernel stack, where the
! parent may have modified them using
! ptrace(POKEUSR). (Note that R0-R2 are
@@ -382,7 +379,7 @@ syscall_trace_entry:
mov.l @(OFF_R5,r15), r5
mov.l @(OFF_R6,r15), r6
mov.l @(OFF_R7,r15), r7 ! arg3
- mov.l @(OFF_R3,r15), r3 ! syscall_nr
+ mov r0, r3 ! syscall_nr, possibly changed to -1
!
mov.l 6f, r10 ! Number of syscalls
cmp/hs r10, r3
diff --git a/arch/sh/kernel/ptrace_32.c b/arch/sh/kernel/ptrace_32.c
index 25ccfbd02bfa..9e86cff041c7 100644
--- a/arch/sh/kernel/ptrace_32.c
+++ b/arch/sh/kernel/ptrace_32.c
@@ -503,7 +503,7 @@ asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
audit_syscall_entry(regs->regs[3], regs->regs[4], regs->regs[5],
regs->regs[6], regs->regs[7]);
- return ret ?: regs->regs[0];
+ return ret ?: regs->regs[3];
}
asmlinkage void do_syscall_trace_leave(struct pt_regs *regs)
