Star64_linux/arch/parisc/kernel
Dmitry V. Levin b7dc5a071d parisc: Fix ptrace syscall number modification
Commit 910cd32e55 ("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 910cd32e55 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: 910cd32e55 ("parisc: Fix and enable seccomp filter support")
Cc: stable@vger.kernel.org # v4.5+
Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
Tested-by: Helge Deller <deller@gmx.de>
Signed-off-by: Helge Deller <deller@gmx.de>
2019-02-21 20:10:46 +01:00
..
syscalls
.gitignore
alternative.c
asm-offsets.c
audit.c
cache.c
compat_audit.c
drivers.c
entry.S
firmware.c
ftrace.c
hardware.c
head.S
hpmc.S
inventory.c
irq.c
Makefile
module.c
pa7300lc.c
pacache.S
parisc_ksyms.c
pci-dma.c
pci.c
pdc_chassis.c
pdc_cons.c
pdt.c
perf.c
perf_asm.S
perf_images.h
process.c
processor.c
ptrace.c
real2.S
setup.c
signal.c
signal32.c
signal32.h
smp.c
stacktrace.c
sys_parisc.c
sys_parisc32.c
syscall.S
time.c
topology.c
traps.c
unaligned.c
unwind.c
vmlinux.lds.S