Add a helper that checks the validity of the file descriptor and
other parameters passed in to epoll_wait().
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
fs/eventpoll.c | 39 +++++++++++++++++++++++++--------------
1 file changed, 25 insertions(+), 14 deletions(-)
diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 67d1808fda0e..14466765b85d 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -2453,6 +2453,27 @@ SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd,
return do_epoll_ctl(epfd, op, fd, &epds, false);
}
+static int ep_check_params(struct file *file, struct epoll_event __user *evs,
+ int maxevents)
+{
+ /* The maximum number of event must be greater than zero */
+ if (maxevents <= 0 || maxevents > EP_MAX_EVENTS)
+ return -EINVAL;
+
+ /* Verify that the area passed by the user is writeable */
+ if (!access_ok(evs, maxevents * sizeof(struct epoll_event)))
+ return -EFAULT;
+
+ /*
+ * We have to check that the file structure underneath the fd
+ * the user passed to us _is_ an eventpoll file.
+ */
+ if (!is_file_epoll(file))
+ return -EINVAL;
+
+ return 0;
+}
+
/*
* Implement the event wait interface for the eventpoll file. It is the kernel
* part of the user space epoll_wait(2).
@@ -2461,26 +2482,16 @@ static int do_epoll_wait(int epfd, struct epoll_event __user *events,
int maxevents, struct timespec64 *to)
{
struct eventpoll *ep;
-
- /* The maximum number of event must be greater than zero */
- if (maxevents <= 0 || maxevents > EP_MAX_EVENTS)
- return -EINVAL;
-
- /* Verify that the area passed by the user is writeable */
- if (!access_ok(events, maxevents * sizeof(struct epoll_event)))
- return -EFAULT;
+ int ret;
/* Get the "struct file *" for the eventpoll file */
CLASS(fd, f)(epfd);
if (fd_empty(f))
return -EBADF;
- /*
- * We have to check that the file structure underneath the fd
- * the user passed to us _is_ an eventpoll file.
- */
- if (!is_file_epoll(fd_file(f)))
- return -EINVAL;
+ ret = ep_check_params(fd_file(f), events, maxevents);
+ if (unlikely(ret))
+ return ret;
/*
* At this point it is safe to assume that the "private_data" contains
--
2.47.2
