[PATCH 3/6] exec: Check for a pending fatal signal instead of core_state

Eric W. Biederman
2021-09-24T00:10:57Z

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.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
---
fs/exec.c | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index a098c133d8d7..b6079f1a098e 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -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;
}
}

--
2.20.1