kernel.git/arch/s390/kernel/traps.c, branch linux-5.18.y

s390/traps: improve panic message for translation-specification exception

2022-03-27T20:18:38Z

There are many different types of translation exceptions but only a translation-specification exception leads to a kernel panic since it indicates corrupted page tables, which must never happen. Improve the panic message so it is a bit more obvious what this is about. Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik

s390/traps: get rid of magic cast for per code

2022-03-07T23:33:01Z

Add a proper union in lowcore to reflect architecture and get rid of a "magic" cast in order to read the full per code. Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik

s390/traps: get rid of magic cast for program interruption code

2022-03-07T23:33:01Z

Add a proper union in lowcore to reflect architecture and get rid of a "magic" cast in order to read the full program interruption code. Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik

s390/extable: add and use fixup_exception helper function

2022-03-07T23:33:00Z

Add and use fixup_exception helper function in order to remove the duplicated exception handler fixup code at several places. Reviewed-by: Alexander Gordeev Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik

s390/extable: move EX_TABLE define to asm-extable.h

2022-03-07T23:33:00Z

Follow arm64 and riscv and move the EX_TABLE define to asm-extable.h which is a lot less generic than the current linkage.h. Also make sure that all files which contain EX_TABLE usages actually include the new header file. This should make sure that the files always compile and there won't be any random compile breakage due to other header file dependencies. Reviewed-by: Alexander Gordeev Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik

s390/extable: sort amode31 extable early

2022-03-07T23:33:00Z

The early program check handler is active before the amode31 extable is sorted. Therefore in case a program check happens early within the amode31 code the extable entry might not be found. Fix this by sorting the amode31 extable early. Signed-off-by: Heiko Carstens Signed-off-by: Vasily Gorbik

signal: Replace force_fatal_sig with force_exit_sig when in doubt

2021-11-19T15:15:58Z

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 Reported-by: kernel test robot [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: 00b06da29cf9 ("signal: Add SA_IMMUTABLE to ensure forced siganls do not get changed") Fixes: a3616a3c0272 ("signal/m68k: Use force_sigsegv(SIGSEGV) in fpsp040_die") Fixes: 83a1f27ad773 ("signal/powerpc: On swapcontext failure force SIGSEGV") Fixes: 9bc508cf0791 ("signal/s390: Use force_sigsegv in default_trap_handler") Fixes: 086ec444f866 ("signal/sparc32: In setup_rt_frame and setup_fram use force_fatal_sig") Fixes: c317d306d550 ("signal/sparc32: Exit with a fatal signal when try_to_clear_window_buffer fails") Fixes: 695dd0d634df ("signal/x86: In emulate_vsyscall force a signal instead of calling do_exit") Fixes: 1fbd60df8a85 ("signal/vm86_32: Properly send SIGSEGV when the vm86 state cannot be saved.") Fixes: 941edc5bf174 ("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 Tested-by: Kees Cook Tested-by: Kyle Huey Signed-off-by: "Eric W. Biederman"

Merge branch 'exit-cleanups-for-v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace

2021-11-11T00:15:54Z

Pull exit cleanups from Eric Biederman: "While looking at some issues related to the exit path in the kernel I found several instances where the code is not using the existing abstractions properly. This set of changes introduces force_fatal_sig a way of sending a signal and not allowing it to be caught, and corrects the misuse of the existing abstractions that I found. A lot of the misuse of the existing abstractions are silly things such as doing something after calling a no return function, rolling BUG by hand, doing more work than necessary to terminate a kernel thread, or calling do_exit(SIGKILL) instead of calling force_sig(SIGKILL). In the review a deficiency in force_fatal_sig and force_sig_seccomp where ptrace or sigaction could prevent the delivery of the signal was found. I have added a change that adds SA_IMMUTABLE to change that makes it impossible to interrupt the delivery of those signals, and allows backporting to fix force_sig_seccomp And Arnd found an issue where a function passed to kthread_run had the wrong prototype, and after my cleanup was failing to build." * 'exit-cleanups-for-v5.16' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (23 commits) soc: ti: fix wkup_m3_rproc_boot_thread return type signal: Add SA_IMMUTABLE to ensure forced siganls do not get changed signal: Replace force_sigsegv(SIGSEGV) with force_fatal_sig(SIGSEGV) exit/r8188eu: Replace the macro thread_exit with a simple return 0 exit/rtl8712: Replace the macro thread_exit with a simple return 0 exit/rtl8723bs: Replace the macro thread_exit with a simple return 0 signal/x86: In emulate_vsyscall force a signal instead of calling do_exit signal/sparc32: In setup_rt_frame and setup_fram use force_fatal_sig signal/sparc32: Exit with a fatal signal when try_to_clear_window_buffer fails exit/syscall_user_dispatch: Send ordinary signals on failure signal: Implement force_fatal_sig exit/kthread: Have kernel threads return instead of calling do_exit signal/s390: Use force_sigsegv in default_trap_handler signal/vm86_32: Properly send SIGSEGV when the vm86 state cannot be saved. signal/vm86_32: Replace open coded BUG_ON with an actual BUG_ON signal/sparc: In setup_tsb_params convert open coded BUG into BUG signal/powerpc: On swapcontext failure force SIGSEGV signal/sh: Use force_sig(SIGKILL) instead of do_group_exit(SIGKILL) signal/mips: Update (_save|_restore)_fp_context to fail with -EFAULT signal/sparc32: Remove unreachable do_exit in do_sparc_fault ...

signal: Replace force_sigsegv(SIGSEGV) with force_fatal_sig(SIGSEGV)

2021-10-29T19:31:34Z

Now that force_fatal_sig exists it is unnecessary and a bit confusing to use force_sigsegv in cases where the simpler force_fatal_sig is wanted. So change every instance we can to make the code clearer. Acked-by: Geert Uytterhoeven Reviewed-by: Philippe Mathieu-Daudé Link: https://lkml.kernel.org/r/877de7jrev.fsf@disp2133 Signed-off-by: "Eric W. Biederman"

signal/s390: Use force_sigsegv in default_trap_handler

2021-10-29T19:31:05Z

Reading the history it is unclear why default_trap_handler calls do_exit. It is not even menthioned in the commit where the change happened. My best guess is that because it is unknown why the exception happened it was desired to guarantee the process never returned to userspace. Using do_exit(SIGSEGV) has the problem that it will only terminate one thread of a process, leaving the process in an undefined state. Use force_sigsegv(SIGSEGV) instead which effectively has the same behavior except that is uses the ordinary signal mechanism and terminates all threads of a process and is generally well defined. Cc: Heiko Carstens Cc: Vasily Gorbik Cc: Christian Borntraeger Cc: linux-s390@vger.kernel.org Fixes: ca2ab03237ec ("[PATCH] s390: core changes") History Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git Reviewed-by: Christian Borntraeger Link: https://lkml.kernel.org/r/20211020174406.17889-11-ebiederm@xmission.com Signed-off-by: Eric W. Biederman