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aio-posix: fix use after leaving scope in aio_poll() 

epoll_handler is a stack variable and must not be accessed after it goes
out of scope:

      if (aio_epoll_check_poll(ctx, pollfds, npfd, timeout)) {
          AioHandler epoll_handler;
          ...
          add_pollfd(&epoll_handler);
          ret = aio_epoll(ctx, pollfds, npfd, timeout);
      } ...

  ...

  /* if we have any readable fds, dispatch event */
  if (ret > 0) {
      for (i = 0; i < npfd; i++) {
          nodes[i]->pfd.revents = pollfds[i].revents;
      }
  }

nodes[0] is &epoll_handler, which has already gone out of scope.

There is no need to use pollfds[] for epoll.  We don't need an
AioHandler for the epoll fd.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Sergio Lopez <slp@redhat.com>
Message-id: 20200214171712.541358-2-stefanha@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Stefan Hajnoczi 2020-02-14 17:17:08 +00:00
parent 8c6b0356b5
commit ff29ed3a33
1 changed files with 8 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
util/aio-posix.c
View File

@ -105,17 +105,18 @@ static void aio_epoll_update(AioContext *ctx, AioHandler *node, bool is_new)
}
}
static int aio_epoll(AioContext *ctx, GPollFD *pfds,
unsigned npfd, int64_t timeout)
static int aio_epoll(AioContext *ctx, int64_t timeout)
{
GPollFD pfd = {
.fd = ctx->epollfd,
.events = G_IO_IN | G_IO_OUT | G_IO_HUP | G_IO_ERR,
};
AioHandler *node;
int i, ret = 0;
struct epoll_event events[128];
assert(npfd == 1);
assert(pfds[0].fd == ctx->epollfd);
if (timeout > 0) {
ret = qemu_poll_ns(pfds, npfd, timeout);
ret = qemu_poll_ns(&pfd, 1, timeout);
}
if (timeout <= 0 || ret > 0) {
ret = epoll_wait(ctx->epollfd, events,
@ -669,13 +670,8 @@ bool aio_poll(AioContext *ctx, bool blocking)
/* wait until next event */
if (aio_epoll_check_poll(ctx, pollfds, npfd, timeout)) {
AioHandler epoll_handler;
epoll_handler.pfd.fd = ctx->epollfd;
epoll_handler.pfd.events = G_IO_IN | G_IO_OUT | G_IO_HUP | G_IO_ERR;
npfd = 0;
add_pollfd(&epoll_handler);
ret = aio_epoll(ctx, pollfds, npfd, timeout);
npfd = 0; /* pollfds[] is not being used */
ret = aio_epoll(ctx, timeout);
} else {
ret = qemu_poll_ns(pollfds, npfd, timeout);
}