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eventpoll: abstract out parameter sanity checking

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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@kernel.dk>
Link: https://lore.kernel.org/r/20250219172552.1565603-2-axboe@kernel.dk
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Jens Axboe 2025-02-19 10:22:24 -07:00 committed by Christian Brauner
parent 2014c95afe
commit 6b47d35d4d
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GPG Key ID: 91C61BC06578DCA2
1 changed files with 25 additions and 14 deletions
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39
fs/eventpoll.c
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@ -2445,6 +2445,27 @@ 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).
@ -2453,26 +2474,16 @@ 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