On Sat, Feb 16, 2019 at 05:55:24PM +0100, Helge Deller wrote: > On 16.02.19 14:10, Dmitry V. Levin wrote: > > Commit 910cd32e552e ("parisc: Fix and enable seccomp filter support") > > introduced a regression in ptrace-based syscall tampering: when tracer > > changes syscall number to -1, the kernel fails to initialize %r28 with > > -ENOSYS and subsequently fails to return the error code of the failed > > syscall to userspace. > > > > This erroneous behaviour could be observed with a simple strace syscall > > fault injection command which is expected to print something like this: > > > > $ strace -a0 -ewrite -einject=write:error=enospc echo hello > > write(1, "hello\n", 6) = -1 ENOSPC (No space left on device) (INJECTED) > > write(2, "echo: ", 6) = -1 ENOSPC (No space left on device) (INJECTED) > > write(2, "write error", 11) = -1 ENOSPC (No space left on device) (INJECTED) > > write(2, "\n", 1) = -1 ENOSPC (No space left on device) (INJECTED) > > +++ exited with 1 +++ > > > > After commit 910cd32e552ea09caa89cdbe328e468979b030dd it loops printing > > something like this instead: > > > > write(1, "hello\n", 6../strace: Failed to tamper with process 12345: unexpectedly got no error (return value 0, error 0) > > ) = 0 (INJECTED) > > > > This bug was found by strace test suite. > > > > Fixes: 910cd32e552e ("parisc: Fix and enable seccomp filter support") > > Cc: stable@vger.kernel.org # v4.5+ > > Signed-off-by: Dmitry V. Levin > > Thanks, the patch works as expected. > You may add: > Tested-by: Helge Deller > > There is an "out" label a few lines below, which should be removed as well. > Otherwise you get this warning: > arch/parisc/kernel/ptrace.c: In function ‘do_syscall_trace_enter’: > arch/parisc/kernel/ptrace.c:357:1: warning: label ‘out’ defined but not used [-Wunused-label] > > I've fixed it up locally and added the patch to my for-next tree. > If it's ok for you, I'll push it through the parisc tree. It's fine with me, thanks! -- ldv