linux/arch/powerpc
Eric W. Biederman fcb116bc43 signal: Replace force_fatal_sig with force_exit_sig when in doubt
Recently to prevent issues with SECCOMP_RET_KILL and similar signals
being changed before they are delivered SA_IMMUTABLE was added.

Unfortunately this broke debuggers[1][2] which reasonably expect
to be able to trap synchronous SIGTRAP and SIGSEGV even when
the target process is not configured to handle those signals.

Add force_exit_sig and use it instead of force_fatal_sig where
historically the code has directly called do_exit.  This has the
implementation benefits of going through the signal exit path
(including generating core dumps) without the danger of allowing
userspace to ignore or change these signals.

This avoids userspace regressions as older kernels exited with do_exit
which debuggers also can not intercept.

In the future is should be possible to improve the quality of
implementation of the kernel by changing some of these force_exit_sig
calls to force_fatal_sig.  That can be done where it matters on
a case-by-case basis with careful analysis.

Reported-by: Kyle Huey <me@kylehuey.com>
Reported-by: kernel test robot <oliver.sang@intel.com>
[1] https://lkml.kernel.org/r/CAP045AoMY4xf8aC_4QU_-j7obuEPYgTcnQQP3Yxk=2X90jtpjw@mail.gmail.com
[2] https://lkml.kernel.org/r/20211117150258.GB5403@xsang-OptiPlex-9020
Fixes: 00b06da29c ("signal: Add SA_IMMUTABLE to ensure forced siganls do not get changed")
Fixes: a3616a3c02 ("signal/m68k: Use force_sigsegv(SIGSEGV) in fpsp040_die")
Fixes: 83a1f27ad7 ("signal/powerpc: On swapcontext failure force SIGSEGV")
Fixes: 9bc508cf07 ("signal/s390: Use force_sigsegv in default_trap_handler")
Fixes: 086ec444f8 ("signal/sparc32: In setup_rt_frame and setup_fram use force_fatal_sig")
Fixes: c317d306d5 ("signal/sparc32: Exit with a fatal signal when try_to_clear_window_buffer fails")
Fixes: 695dd0d634 ("signal/x86: In emulate_vsyscall force a signal instead of calling do_exit")
Fixes: 1fbd60df8a ("signal/vm86_32: Properly send SIGSEGV when the vm86 state cannot be saved.")
Fixes: 941edc5bf1 ("exit/syscall_user_dispatch: Send ordinary signals on failure")
Link: https://lkml.kernel.org/r/871r3dqfv8.fsf_-_@email.froward.int.ebiederm.org
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Kees Cook <keescook@chromium.org>
Tested-by: Kyle Huey <khuey@kylehuey.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2021-11-19 09:15:58 -06:00
..
boot powerpc updates for 5.16 2021-11-05 08:15:46 -07:00
configs Merge branch 'akpm' (patches from Andrew) 2021-11-06 14:08:17 -07:00
crypto crypto: powepc/sha1 - remove unneeded semicolon 2021-03-07 15:13:14 +11:00
include asm-generic: asm/syscall.h cleanup 2021-11-10 11:22:03 -08:00
kernel signal: Replace force_fatal_sig with force_exit_sig when in doubt 2021-11-19 09:15:58 -06:00
kexec powerpc/machdep: Remove stale functions from ppc_md structure 2021-10-22 15:22:05 +11:00
kvm mm/migrate.c: remove MIGRATE_PFN_LOCKED 2021-11-11 09:34:35 -08:00
lib Kbuild updates for v5.16 2021-11-08 09:15:45 -08:00
math-emu powerpc/64s: avoid reloading (H)SRR registers if they are still valid 2021-06-25 00:06:55 +10:00
mm Merge branch 'akpm' (patches from Andrew) 2021-11-09 10:11:53 -08:00
net powerpc updates for 5.16 2021-11-05 08:15:46 -07:00
perf powerpc updates for 5.16 2021-11-05 08:15:46 -07:00
platforms cxl for v5.16 2021-11-08 11:49:48 -08:00
purgatory powerpc/kexec: Don't use .machine ppc64 in trampoline_64.S 2021-04-08 21:17:43 +10:00
sysdev powerpc updates for 5.16 2021-11-05 08:15:46 -07:00
tools powerpc/head_check: Fix shellcheck errors 2021-08-17 22:52:02 +10:00
xmon powerpc/xmon: fix task state output 2021-10-28 22:32:03 +11:00
Kbuild kbuild: use more subdir- for visiting subdirectories while cleaning 2021-10-24 13:49:46 +09:00
Kconfig powerpc/64s: Default to 64K pages for 64 bit book3s 2021-10-27 22:31:22 +11:00
Kconfig.debug powerpc/ptdump: Convert powerpc to GENERIC_PTDUMP 2021-08-25 13:35:48 +10:00
Makefile Kbuild updates for v5.16 2021-11-08 09:15:45 -08:00
Makefile.postlink