diff options
| author | Dylan Yudaken <dylany@fb.com> | 2022-08-16 06:59:59 -0700 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2022-09-21 10:30:42 -0600 |
| commit | 9f0deaa12d832f488500a5afe9b912e9b3cfc432 (patch) | |
| tree | 98e270c4c922f03493e59cd0bf64854e9b10d55f /fs/eventfd.c | |
| parent | 521a547ced6477c54b4b0cc206000406c221b4d6 (diff) | |
eventfd: guard wake_up in eventfd fs calls as well
Guard wakeups that the user can trigger, and that may end up triggering a
call back into eventfd_signal. This is in addition to the current approach
that only guards in eventfd_signal.
Rename in_eventfd_signal -> in_eventfd at the same time to reflect this.
Without this there would be a deadlock in the following code using libaio:
int main()
{
struct io_context *ctx = NULL;
struct iocb iocb;
struct iocb *iocbs[] = { &iocb };
int evfd;
uint64_t val = 1;
evfd = eventfd(0, EFD_CLOEXEC);
assert(!io_setup(2, &ctx));
io_prep_poll(&iocb, evfd, POLLIN);
io_set_eventfd(&iocb, evfd);
assert(1 == io_submit(ctx, 1, iocbs));
write(evfd, &val, 8);
}
Signed-off-by: Dylan Yudaken <dylany@fb.com>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/20220816135959.1490641-1-dylany@fb.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'fs/eventfd.c')
| -rw-r--r-- | fs/eventfd.c | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/fs/eventfd.c b/fs/eventfd.c index 3627dd7d25db..c0ffee99ad23 100644 --- a/fs/eventfd.c +++ b/fs/eventfd.c @@ -69,17 +69,17 @@ __u64 eventfd_signal(struct eventfd_ctx *ctx, __u64 n) * it returns false, the eventfd_signal() call should be deferred to a * safe context. */ - if (WARN_ON_ONCE(current->in_eventfd_signal)) + if (WARN_ON_ONCE(current->in_eventfd)) return 0; spin_lock_irqsave(&ctx->wqh.lock, flags); - current->in_eventfd_signal = 1; + current->in_eventfd = 1; if (ULLONG_MAX - ctx->count < n) n = ULLONG_MAX - ctx->count; ctx->count += n; if (waitqueue_active(&ctx->wqh)) wake_up_locked_poll(&ctx->wqh, EPOLLIN); - current->in_eventfd_signal = 0; + current->in_eventfd = 0; spin_unlock_irqrestore(&ctx->wqh.lock, flags); return n; @@ -253,8 +253,10 @@ static ssize_t eventfd_read(struct kiocb *iocb, struct iov_iter *to) __set_current_state(TASK_RUNNING); } eventfd_ctx_do_read(ctx, &ucnt); + current->in_eventfd = 1; if (waitqueue_active(&ctx->wqh)) wake_up_locked_poll(&ctx->wqh, EPOLLOUT); + current->in_eventfd = 0; spin_unlock_irq(&ctx->wqh.lock); if (unlikely(copy_to_iter(&ucnt, sizeof(ucnt), to) != sizeof(ucnt))) return -EFAULT; @@ -301,8 +303,10 @@ static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t c } if (likely(res > 0)) { ctx->count += ucnt; + current->in_eventfd = 1; if (waitqueue_active(&ctx->wqh)) wake_up_locked_poll(&ctx->wqh, EPOLLIN); + current->in_eventfd = 0; } spin_unlock_irq(&ctx->wqh.lock); |