Commit 7e3c4fb7 authored Sep 03, 2021 by Eric W. Biederman

exec: Check for a pending fatal signal instead of core_state

Prevent exec continuing when a fatal signal is pending by replacing
mmap_read_lock with mmap_read_lock_killable.  This is always the right
thing to do as userspace will never observe an exec complete when
there is a fatal signal pending.

With that change it becomes unnecessary to explicitly test for a core
dump in progress.  In coredump_wait zap_threads arranges under
mmap_write_lock for all tasks that use a mm to also have SIGKILL
pending, which means mmap_read_lock_killable will always return -EINTR
when old_mm->core_state is present.

Link: https://lkml.kernel.org/r/87fstux27w.fsf@disp2133


Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

parent 4f627af8

fs/exec.c

+6 −8

Original line number	Diff line number	Diff line
		@@ -987,16 +987,14 @@ static int exec_mmap(struct mm_struct *mm)

		if (old_mm) {
		/*
		* Make sure that if there is a core dump in progress
		* for the old mm, we get out and die instead of going
		* through with the exec. We must hold mmap_lock around
		* checking core_state and changing tsk->mm.
		* If there is a pending fatal signal perhaps a signal
		* whose default action is to create a coredump get
		* out and die instead of going through with the exec.
		*/
		mmap_read_lock(old_mm);
		if (unlikely(old_mm->core_state)) {
		mmap_read_unlock(old_mm);
		ret = mmap_read_lock_killable(old_mm);
		if (ret) {
		up_write(&tsk->signal->exec_update_lock);
		return -EINTR;
		return ret;
		}
		}