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authorJann Horn <jannh@google.com>2018-08-21 22:00:58 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2018-08-22 10:52:51 -0700
commit06e62a46bbba20aa5286102016a04214bb446141 (patch)
tree614724f8bb48c794cf575e886fc540d0464c9a0f /kernel
parent20ab7218d2507b2dbec9c053c2f1b96054e266b6 (diff)
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fork: don't copy inconsistent signal handler state to child
Before this change, if a multithreaded process forks while one of its threads is changing a signal handler using sigaction(), the memcpy() in copy_sighand() can race with the struct assignment in do_sigaction(). It isn't clear whether this can cause corruption of the userspace signal handler pointer, but it definitely can cause inconsistency between different fields of struct sigaction. Take the appropriate spinlock to avoid this. I have tested that this patch prevents inconsistency between sa_sigaction and sa_flags, which is possible before this patch. Link: http://lkml.kernel.org/r/20180702145108.73189-1-jannh@google.com Signed-off-by: Jann Horn <jannh@google.com> Acked-by: Michal Hocko <mhocko@suse.com> Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Cc: Rik van Riel <riel@redhat.com> Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org> Cc: Kees Cook <keescook@chromium.org> Cc: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/fork.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/fork.c b/kernel/fork.c
index 8bcef2413f1b..23eb960c701d 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1427,7 +1427,9 @@ static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk)
return -ENOMEM;
atomic_set(&sig->count, 1);
+ spin_lock_irq(&current->sighand->siglock);
memcpy(sig->action, current->sighand->action, sizeof(sig->action));
+ spin_unlock_irq(&current->sighand->siglock);
return 0;
}