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-rw-r--r--fs/pipe.c36
1 files changed, 29 insertions, 7 deletions
diff --git a/fs/pipe.c b/fs/pipe.c
index 87109e761fa5..04d004ee2e8c 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -364,17 +364,39 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to)
ret = -EAGAIN;
break;
}
- if (signal_pending(current)) {
- if (!ret)
- ret = -ERESTARTSYS;
- break;
- }
__pipe_unlock(pipe);
- if (was_full) {
+
+ /*
+ * We only get here if we didn't actually read anything.
+ *
+ * However, we could have seen (and removed) a zero-sized
+ * pipe buffer, and might have made space in the buffers
+ * that way.
+ *
+ * You can't make zero-sized pipe buffers by doing an empty
+ * write (not even in packet mode), but they can happen if
+ * the writer gets an EFAULT when trying to fill a buffer
+ * that already got allocated and inserted in the buffer
+ * array.
+ *
+ * So we still need to wake up any pending writers in the
+ * _very_ unlikely case that the pipe was full, but we got
+ * no data.
+ */
+ if (unlikely(was_full)) {
wake_up_interruptible_sync_poll(&pipe->wait, EPOLLOUT | EPOLLWRNORM);
kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
}
- wait_event_interruptible(pipe->wait, pipe_readable(pipe));
+
+ /*
+ * But because we didn't read anything, at this point we can
+ * just return directly with -ERESTARTSYS if we're interrupted,
+ * since we've done any required wakeups and there's no need
+ * to mark anything accessed. And we've dropped the lock.
+ */
+ if (wait_event_interruptible(pipe->wait, pipe_readable(pipe)) < 0)
+ return -ERESTARTSYS;
+
__pipe_lock(pipe);
was_full = pipe_full(pipe->head, pipe->tail, pipe->max_usage);
}