user/sven/linux.git/kernel/signal.c, branch v4.14.149

kernel/signal.c: trace_signal_deliver when signal_group_exit

2019-06-09T07:18:17Z

commit 98af37d624ed8c83f1953b1b6b2f6866011fc064 upstream. In the fixes commit, removing SIGKILL from each thread signal mask and executing "goto fatal" directly will skip the call to "trace_signal_deliver". At this point, the delivery tracking of the SIGKILL signal will be inaccurate. Therefore, we need to add trace_signal_deliver before "goto fatal" after executing sigdelset. Note: SEND_SIG_NOINFO matches the fact that SIGKILL doesn't have any info. Link: http://lkml.kernel.org/r/20190425025812.91424-1-weizhenliang@huawei.com Fixes: cf43a757fd4944 ("signal: Restore the stop PTRACE_EVENT_EXIT") Signed-off-by: Zhenliang Wei Reviewed-by: Christian Brauner Reviewed-by: Oleg Nesterov Cc: Eric W. Biederman Cc: Ivan Delalande Cc: Arnd Bergmann Cc: Thomas Gleixner Cc: Deepa Dinamani Cc: Greg Kroah-Hartman Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

signal: Restore the stop PTRACE_EVENT_EXIT

2019-02-20T09:20:54Z

commit cf43a757fd49442bc38f76088b70c2299eed2c2f upstream. In the middle of do_exit() there is there is a call "ptrace_event(PTRACE_EVENT_EXIT, code);" That call places the process in TACKED_TRACED aka "(TASK_WAKEKILL | __TASK_TRACED)" and waits for for the debugger to release the task or SIGKILL to be delivered. Skipping past dequeue_signal when we know a fatal signal has already been delivered resulted in SIGKILL remaining pending and TIF_SIGPENDING remaining set. This in turn caused the scheduler to not sleep in PTACE_EVENT_EXIT as it figured a fatal signal was pending. This also caused ptrace_freeze_traced in ptrace_check_attach to fail because it left a per thread SIGKILL pending which is what fatal_signal_pending tests for. This difference in signal state caused strace to report strace: Exit of unknown pid NNNNN ignored Therefore update the signal handling state like dequeue_signal would when removing a per thread SIGKILL, by removing SIGKILL from the per thread signal mask and clearing TIF_SIGPENDING. Acked-by: Oleg Nesterov Reported-by: Oleg Nesterov Reported-by: Ivan Delalande Cc: stable@vger.kernel.org Fixes: 35634ffa1751 ("signal: Always notice exiting tasks") Signed-off-by: "Eric W. Biederman" Signed-off-by: Greg Kroah-Hartman

signal: Better detection of synchronous signals

2019-02-15T07:09:11Z

commit 7146db3317c67b517258cb5e1b08af387da0618b upstream. Recently syzkaller was able to create unkillablle processes by creating a timer that is delivered as a thread local signal on SIGHUP, and receiving SIGHUP SA_NODEFERER. Ultimately causing a loop failing to deliver SIGHUP but always trying. When the stack overflows delivery of SIGHUP fails and force_sigsegv is called. Unfortunately because SIGSEGV is numerically higher than SIGHUP next_signal tries again to deliver a SIGHUP. From a quality of implementation standpoint attempting to deliver the timer SIGHUP signal is wrong. We should attempt to deliver the synchronous SIGSEGV signal we just forced. We can make that happening in a fairly straight forward manner by instead of just looking at the signal number we also look at the si_code. In particular for exceptions (aka synchronous signals) the si_code is always greater than 0. That still has the potential to pick up a number of asynchronous signals as in a few cases the same si_codes that are used for synchronous signals are also used for asynchronous signals, and SI_KERNEL is also included in the list of possible si_codes. Still the heuristic is much better and timer signals are definitely excluded. Which is enough to prevent all known ways for someone sending a process signals fast enough to cause unexpected and arguably incorrect behavior. Cc: stable@vger.kernel.org Fixes: a27341cd5fcb ("Prioritize synchronous signals over 'normal' signals") Tested-by: Dmitry Vyukov Reported-by: Dmitry Vyukov Signed-off-by: "Eric W. Biederman" Signed-off-by: Greg Kroah-Hartman

signal: Always notice exiting tasks

2019-02-15T07:09:11Z

commit 35634ffa1751b6efd8cf75010b509dcb0263e29b upstream. Recently syzkaller was able to create unkillablle processes by creating a timer that is delivered as a thread local signal on SIGHUP, and receiving SIGHUP SA_NODEFERER. Ultimately causing a loop failing to deliver SIGHUP but always trying. Upon examination it turns out part of the problem is actually most of the solution. Since 2.5 signal delivery has found all fatal signals, marked the signal group for death, and queued SIGKILL in every threads thread queue relying on signal->group_exit_code to preserve the information of which was the actual fatal signal. The conversion of all fatal signals to SIGKILL results in the synchronous signal heuristic in next_signal kicking in and preferring SIGHUP to SIGKILL. Which is especially problematic as all fatal signals have already been transformed into SIGKILL. Instead of dequeueing signals and depending upon SIGKILL to be the first signal dequeued, first test if the signal group has already been marked for death. This guarantees that nothing in the signal queue can prevent a process that needs to exit from exiting. Cc: stable@vger.kernel.org Tested-by: Dmitry Vyukov Reported-by: Dmitry Vyukov Ref: ebf5ebe31d2c ("[PATCH] signal-fixes-2.5.59-A4") History Tree: https://git.kernel.org/pub/scm/linux/kernel/git/tglx/history.git Signed-off-by: "Eric W. Biederman" Signed-off-by: Greg Kroah-Hartman

signal: Guard against negative signal numbers in copy_siginfo_from_user32

2018-11-13T19:15:07Z

commit a36700589b85443e28170be59fa11c8a104130a5 upstream. While fixing an out of bounds array access in known_siginfo_layout reported by the kernel test robot it became apparent that the same bug exists in siginfo_layout and affects copy_siginfo_from_user32. The straight forward fix that makes guards against making this mistake in the future and should keep the code size small is to just take an unsigned signal number instead of a signed signal number, as I did to fix known_siginfo_layout. Cc: stable@vger.kernel.org Fixes: cc731525f26a ("signal: Remove kernel interal si_code magic") Signed-off-by: "Eric W. Biederman" Signed-off-by: Greg Kroah-Hartman

signal: Always deliver the kernel's SIGKILL and SIGSTOP to a pid namespace init

2018-11-13T19:15:00Z

[ Upstream commit 3597dfe01d12f570bc739da67f857fd222a3ea66 ] Instead of playing whack-a-mole and changing SEND_SIG_PRIV to SEND_SIG_FORCED throughout the kernel to ensure a pid namespace init gets signals sent by the kernel, stop allowing a pid namespace init to ignore SIGKILL or SIGSTOP sent by the kernel. A pid namespace init is only supposed to be able to ignore signals sent from itself and children with SIG_DFL. Fixes: 921cf9f63089 ("signals: protect cinit from unblocked SIG_DFL signals") Reviewed-by: Thomas Gleixner Signed-off-by: "Eric W. Biederman" Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

signal: Introduce COMPAT_SIGMINSTKSZ for use in compat_sys_sigaltstack

2018-11-13T19:14:54Z

[ Upstream commit 22839869f21ab3850fbbac9b425ccc4c0023926f ] The sigaltstack(2) system call fails with -ENOMEM if the new alternative signal stack is found to be smaller than SIGMINSTKSZ. On architectures such as arm64, where the native value for SIGMINSTKSZ is larger than the compat value, this can result in an unexpected error being reported to a compat task. See, for example: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=904385 This patch fixes the problem by extending do_sigaltstack to take the minimum signal stack size as an additional parameter, allowing the native and compat system call entry code to pass in their respective values. COMPAT_SIGMINSTKSZ is just defined as SIGMINSTKSZ if it has not been defined by the architecture. Cc: Arnd Bergmann Cc: Dominik Brodowski Cc: "Eric W. Biederman" Cc: Andrew Morton Cc: Al Viro Cc: Oleg Nesterov Reported-by: Steve McIntyre Tested-by: Steve McIntyre <93sam@debian.org> Signed-off-by: Will Deacon Signed-off-by: Catalin Marinas Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

sched/core: Introduce set_special_state()

2018-06-20T19:02:54Z

[ Upstream commit b5bf9a90bbebffba888c9144c5a8a10317b04064 ] Gaurav reported a perceived problem with TASK_PARKED, which turned out to be a broken wait-loop pattern in __kthread_parkme(), but the reported issue can (and does) in fact happen for states that do not do condition based sleeps. When the 'current->state = TASK_RUNNING' store of a previous (concurrent) try_to_wake_up() collides with the setting of a 'special' sleep state, we can loose the sleep state. Normal condition based wait-loops are immune to this problem, but for sleep states that are not condition based are subject to this problem. There already is a fix for TASK_DEAD. Abstract that and also apply it to TASK_STOPPED and TASK_TRACED, both of which are also without condition based wait-loop. Reported-by: Gaurav Kohli Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Oleg Nesterov Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Signed-off-by: Ingo Molnar Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

kmemcheck: stop using GFP_NOTRACK and SLAB_NOTRACK

2018-02-22T14:42:23Z

commit 75f296d93bcebcfe375884ddac79e30263a31766 upstream. Convert all allocations that used a NOTRACK flag to stop using it. Link: http://lkml.kernel.org/r/20171007030159.22241-3-alexander.levin@verizon.com Signed-off-by: Sasha Levin Cc: Alexander Potapenko Cc: Eric W. Biederman Cc: Michal Hocko Cc: Pekka Enberg Cc: Steven Rostedt Cc: Tim Hansen Cc: Vegard Nossum Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

kernel/signal.c: remove the no longer needed SIGNAL_UNKILLABLE check in complete_signal()

2018-01-10T08:31:20Z

commit 426915796ccaf9c2bd9bb06dc5702225957bc2e5 upstream. complete_signal() checks SIGNAL_UNKILLABLE before it starts to destroy the thread group, today this is wrong in many ways. If nothing else, fatal_signal_pending() should always imply that the whole thread group (except ->group_exit_task if it is not NULL) is killed, this check breaks the rule. After the previous changes we can rely on sig_task_ignored(); sig_fatal(sig) && SIGNAL_UNKILLABLE can only be true if we actually want to kill this task and sig == SIGKILL OR it is traced and debugger can intercept the signal. This should hopefully fix the problem reported by Dmitry. This test-case static int init(void *arg) { for (;;) pause(); } int main(void) { char stack[16 * 1024]; for (;;) { int pid = clone(init, stack + sizeof(stack)/2, CLONE_NEWPID | SIGCHLD, NULL); assert(pid > 0); assert(ptrace(PTRACE_ATTACH, pid, 0, 0) == 0); assert(waitpid(-1, NULL, WSTOPPED) == pid); assert(ptrace(PTRACE_DETACH, pid, 0, SIGSTOP) == 0); assert(syscall(__NR_tkill, pid, SIGKILL) == 0); assert(pid == wait(NULL)); } } triggers the WARN_ON_ONCE(!(task->jobctl & JOBCTL_STOP_PENDING)) in task_participate_group_stop(). do_signal_stop()->signal_group_exit() checks SIGNAL_GROUP_EXIT and return false, but task_set_jobctl_pending() checks fatal_signal_pending() and does not set JOBCTL_STOP_PENDING. And his should fix the minor security problem reported by Kyle, SECCOMP_RET_TRACE can miss fatal_signal_pending() the same way if the task is the root of a pid namespace. Link: http://lkml.kernel.org/r/20171103184246.GD21036@redhat.com Signed-off-by: Oleg Nesterov Reported-by: Dmitry Vyukov Reported-by: Kyle Huey Reviewed-by: Kees Cook Tested-by: Kyle Huey Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman