swh:1:snp:c2847dfd741eae21606027cf29250d1ebcd63fb4
Revision 4ab6c08336535f8c8e42cf45d7adeda882eff06e authored by Oleg Nesterov on 26 August 2009, 21:29:24 UTC, committed by Linus Torvalds on 27 August 2009, 03:06:52 UTC
Spotted by Hiroshi Shimamoto who also provided the test-case below. copy_process() uses signal->count as a reference counter, but it is not. This test case #include <sys/types.h> #include <sys/wait.h> #include <unistd.h> #include <stdio.h> #include <errno.h> #include <pthread.h> void *null_thread(void *p) { for (;;) sleep(1); return NULL; } void *exec_thread(void *p) { execl("/bin/true", "/bin/true", NULL); return null_thread(p); } int main(int argc, char **argv) { for (;;) { pid_t pid; int ret, status; pid = fork(); if (pid < 0) break; if (!pid) { pthread_t tid; pthread_create(&tid, NULL, exec_thread, NULL); for (;;) pthread_create(&tid, NULL, null_thread, NULL); } do { ret = waitpid(pid, &status, 0); } while (ret == -1 && errno == EINTR); } return 0; } quickly creates an unkillable task. If copy_process(CLONE_THREAD) races with de_thread() copy_signal()->atomic(signal->count) breaks the signal->notify_count logic, and the execing thread can hang forever in kernel space. Change copy_process() to increment count/live only when we know for sure we can't fail. In this case the forked thread will take care of its reference to signal correctly. If copy_process() fails, check CLONE_THREAD flag. If it it set - do nothing, the counters were not changed and current belongs to the same thread group. If it is not set, ->signal must be released in any case (and ->count must be == 1), the forked child is the only thread in the thread group. We need more cleanups here, in particular signal->count should not be used by de_thread/__exit_signal at all. This patch only fixes the bug. Reported-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Tested-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Roland McGrath <roland@redhat.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Tip revision: 53d5fc89d66a778577295020dc57bb3ccec84354 authored by Linus Torvalds on 01 October 2021, 21:45:23 UTC
Merge tag 's390-5.15-4' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux
Merge tag 's390-5.15-4' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux
Tip revision: 53d5fc8
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COPYING | -rw-r--r-- | 18.3 KB |
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Makefile | -rw-r--r-- | 53.9 KB |
README | -rw-r--r-- | 17.0 KB |
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