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Filename Latest commit message Latest commit date
Oleg Nesterov 1695fca8a9 ptrace: fix task_join_group_stop() for the case when current is traced
commit 7b3c36fc4c231ca532120bbc0df67a12f09c1d96 upstream.

This testcase

	#include <stdio.h>
	#include <unistd.h>
	#include <signal.h>
	#include <sys/ptrace.h>
	#include <sys/wait.h>
	#include <pthread.h>
	#include <assert.h>

	void *tf(void *arg)
	{
		return NULL;
	}

	int main(void)
	{
		int pid = fork();
		if (!pid) {
			kill(getpid(), SIGSTOP);

			pthread_t th;
			pthread_create(&th, NULL, tf, NULL);

			return 0;
		}

		waitpid(pid, NULL, WSTOPPED);

		ptrace(PTRACE_SEIZE, pid, 0, PTRACE_O_TRACECLONE);
		waitpid(pid, NULL, 0);

		ptrace(PTRACE_CONT, pid, 0,0);
		waitpid(pid, NULL, 0);

		int status;
		int thread = waitpid(-1, &status, 0);
		assert(thread > 0 && thread != pid);
		assert(status == 0x80137f);

		return 0;
	}

fails and triggers WARN_ON_ONCE(!signr) in do_jobctl_trap().

This is because task_join_group_stop() has 2 problems when current is traced:

	1. We can't rely on the "JOBCTL_STOP_PENDING" check, a stopped tracee
	   can be woken up by debugger and it can clone another thread which
	   should join the group-stop.

	   We need to check group_stop_count || SIGNAL_STOP_STOPPED.

	2. If SIGNAL_STOP_STOPPED is already set, we should not increment
	   sig->group_stop_count and add JOBCTL_STOP_CONSUME. The new thread
	   should stop without another do_notify_parent_cldstop() report.

To clarify, the problem is very old and we should blame
ptrace_init_task().  But now that we have task_join_group_stop() it makes
more sense to fix this helper to avoid the code duplication.

Reported-by: syzbot+3485e3773f7da290eecc@syzkaller.appspotmail.com
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Christian Brauner <christian@brauner.io>
Cc: "Eric W . Biederman" <ebiederm@xmission.com>
Cc: Zhiqiang Liu <liuzhiqiang26@huawei.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20201019134237.GA18810@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-11-10 12:37:24 +01:00
arch arm64: Change .weak to SYM_FUNC_START_WEAK_PI for arch/arm64/lib/mem*.S 2020-11-10 12:37:24 +01:00
block block: ratelimit handle_bad_sector() message 2020-10-29 09:58:01 +01:00
certs
crypto crypto: algif_skcipher - EBUSY on aio should be an error 2020-10-29 09:57:30 +01:00
Documentation linkage: Introduce new macros for assembler symbols 2020-11-10 12:37:24 +01:00
drivers drm/i915: Drop runtime-pm assert from vgpu io accessors 2020-11-10 12:37:23 +01:00
fs cachefiles: Handle readpage error correctly 2020-11-05 11:43:36 +01:00
include linkage: Introduce new macros for assembler symbols 2020-11-10 12:37:24 +01:00
init printk: reduce LOG_BUF_SHIFT range for H8300 2020-11-05 11:43:16 +01:00
ipc ipc/util.c: sysvipc_find_ipc() incorrectly updates position index 2020-05-20 08:20:16 +02:00
kernel ptrace: fix task_join_group_stop() for the case when current is traced 2020-11-10 12:37:24 +01:00
lib sgl_alloc_order: fix memory leak 2020-11-05 11:43:22 +01:00
LICENSES
mm mm/page_owner: change split_page_owner to take a count 2020-10-29 09:57:52 +01:00
net tipc: fix use-after-free in tipc_bcast_get_mode 2020-11-10 12:37:24 +01:00
samples samples/bpf: Fix possible deadlock in xdpsock 2020-11-05 11:43:17 +01:00
scripts scripts/setlocalversion: make git describe output more reliable 2020-11-01 12:01:01 +01:00
security evm: Check size of security.evm before using it 2020-11-01 12:01:05 +01:00
sound ASoC: Intel: Skylake: Add alternative topology binary name 2020-11-10 12:37:23 +01:00
tools perf python scripting: Fix printable strings in python3 scripts 2020-11-05 11:43:32 +01:00
usr
virt KVM: arm64: Assume write fault on S1PTW permission fault on instruction fetch 2020-10-01 13:18:25 +02:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS Documentation/llvm: add documentation on building w/ Clang/LLVM 2020-08-26 10:40:46 +02:00
Makefile Linux 5.4.75 2020-11-05 11:43:38 +01:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
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In order to build the documentation, use ``make htmldocs`` or
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    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
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the problems which may result by upgrading your kernel.