[v16,08/20] io: add qio_channel_readv_full_all_eof & qio_channel_readv_full_all helpers

Commit Message

Jag Raman Jan. 11, 2021, 5:05 a.m. UTC

From: Elena Ufimtseva <[e-mail]>

Adds qio_channel_readv_full_all_eof() and qio_channel_readv_full_all()
to read both data and FDs. Refactors existing code to use these helpers.

Signed-off-by: Elena Ufimtseva <[e-mail]>
Signed-off-by: John G Johnson <[e-mail]>
Signed-off-by: Jagannathan Raman <[e-mail]>
---
 include/io/channel.h | 51 ++++++++++++++++++++++++++++++++++++
 io/channel.c         | 73 ++++++++++++++++++++++++++++++++++++++++------------
 2 files changed, 107 insertions(+), 17 deletions(-)

Comments

Stefan Hajnoczi Jan. 12, 2021, 11:15 a.m. UTC | #1

On Mon, Jan 11, 2021 at 12:05:53AM -0500, Jagannathan Raman wrote:
> @@ -112,20 +132,36 @@ int qio_channel_readv_all_eof(QIOChannel *ioc,
>                  qio_channel_wait(ioc, G_IO_IN);
>              }
>              continue;
> -        } else if (len < 0) {
> -            goto cleanup;
> -        } else if (len == 0) {
> -            if (partial) {
> -                error_setg(errp,
> -                           "Unexpected end-of-file before all bytes were read");
> -            } else {
> -                ret = 0;
> +        }
> +
> +        if (len <= 0) {
> +            size_t fd_idx = nfds ? *nfds : 0;

This loads uninitialized memory when len < 0 and the caller has not
initialized *nfds because qio_channel_readv_full() does not set *nfds =
0 in the failure case.

qio_channel_readv_full() should clear nfds at the start of the function:

  if (nfds) {
      *nfds = 0;
  }

> +            if (len == 0) {
> +                if (partial) {
> +                    error_setg(errp,
> +                               "Unexpected end-of-file before all bytes were read");
> +                } else {
> +                    ret = 0;
> +                }
> +            }
> +
> +            while (fds && fd_idx) {
> +                close(*fds[fd_idx - 1]);

The type of fds is int **. Taking operator precedence into account, we
get:

  int *ptr = fds[fd_idx - 1]; /* fds = {&int1, &int2, &int3, ...} */
  close(*ptr);

That is not the intended behavior. I think this should be:

  close((*fds)[fd_idx - 1]);

> +                fd_idx--;
> +            }
> +
> +            if (fds) {
> +                g_free(*fds);
>              }
> +
>              goto cleanup;

Please clear fds and nfds so there is no way the caller can accidentally
use the freed values.

Patch

diff --git a/include/io/channel.h b/include/io/channel.h
index 2a45fb5..31e4164 100644
--- a/include/io/channel.h
+++ b/include/io/channel.h
@@ -775,6 +775,57 @@  void qio_channel_set_aio_fd_handler(QIOChannel *ioc,
                                     void *opaque);
 
 /**
+ * qio_channel_readv_full_all_eof:
+ * @ioc: the channel object
+ * @iov: the array of memory regions to read data to
+ * @niov: the length of the @iov array
+ * @fds: an array of file handles to read
+ * @nfds: number of file handles in @fds
+ * @errp: pointer to a NULL-initialized error object
+ *
+ *
+ * Performs same function as qio_channel_readv_all_eof.
+ * Additionally, attempts to read file descriptors shared
+ * over the channel. The function will wait for all
+ * requested data to be read, yielding from the current
+ * coroutine if required.
+ *
+ * Returns: 1 if all bytes were read, 0 if end-of-file
+ *          occurs without data, or -1 on error
+ */
+
+int qio_channel_readv_full_all_eof(QIOChannel *ioc,
+                                   const struct iovec *iov,
+                                   size_t niov,
+                                   int **fds, size_t *nfds,
+                                   Error **errp);
+
+/**
+ * qio_channel_readv_full_all:
+ * @ioc: the channel object
+ * @iov: the array of memory regions to read data to
+ * @niov: the length of the @iov array
+ * @fds: an array of file handles to read
+ * @nfds: number of file handles in @fds
+ * @errp: pointer to a NULL-initialized error object
+ *
+ *
+ * Performs same function as qio_channel_readv_all_eof.
+ * Additionally, attempts to read file descriptors shared
+ * over the channel. The function will wait for all
+ * requested data to be read, yielding from the current
+ * coroutine if required.
+ *
+ * Returns: 0 if all bytes were read, or -1 on error
+ */
+
+int qio_channel_readv_full_all(QIOChannel *ioc,
+                               const struct iovec *iov,
+                               size_t niov,
+                               int **fds, size_t *nfds,
+                               Error **errp);
+
+/**
  * qio_channel_writev_full_all:
  * @ioc: the channel object
  * @iov: the array of memory regions to write data from
diff --git a/io/channel.c b/io/channel.c
index 0d4b8b5..09ec31e 100644
--- a/io/channel.c
+++ b/io/channel.c
@@ -92,10 +92,29 @@  int qio_channel_readv_all_eof(QIOChannel *ioc,
                               size_t niov,
                               Error **errp)
 {
+    return qio_channel_readv_full_all_eof(ioc, iov, niov, NULL, NULL, errp);
+}
+
+int qio_channel_readv_all(QIOChannel *ioc,
+                          const struct iovec *iov,
+                          size_t niov,
+                          Error **errp)
+{
+    return qio_channel_readv_full_all(ioc, iov, niov, NULL, NULL, errp);
+}
+
+int qio_channel_readv_full_all_eof(QIOChannel *ioc,
+                                   const struct iovec *iov,
+                                   size_t niov,
+                                   int **fds, size_t *nfds,
+                                   Error **errp)
+{
     int ret = -1;
     struct iovec *local_iov = g_new(struct iovec, niov);
     struct iovec *local_iov_head = local_iov;
     unsigned int nlocal_iov = niov;
+    int **local_fds = fds;
+    size_t *local_nfds = nfds;
     bool partial = false;
 
     nlocal_iov = iov_copy(local_iov, nlocal_iov,
@@ -104,7 +123,8 @@  int qio_channel_readv_all_eof(QIOChannel *ioc,
 
     while (nlocal_iov > 0) {
         ssize_t len;
-        len = qio_channel_readv(ioc, local_iov, nlocal_iov, errp);
+        len = qio_channel_readv_full(ioc, local_iov, nlocal_iov, local_fds,
+                                     local_nfds, errp);
         if (len == QIO_CHANNEL_ERR_BLOCK) {
             if (qemu_in_coroutine()) {
                 qio_channel_yield(ioc, G_IO_IN);
@@ -112,20 +132,36 @@  int qio_channel_readv_all_eof(QIOChannel *ioc,
                 qio_channel_wait(ioc, G_IO_IN);
             }
             continue;
-        } else if (len < 0) {
-            goto cleanup;
-        } else if (len == 0) {
-            if (partial) {
-                error_setg(errp,
-                           "Unexpected end-of-file before all bytes were read");
-            } else {
-                ret = 0;
+        }
+
+        if (len <= 0) {
+            size_t fd_idx = nfds ? *nfds : 0;
+            if (len == 0) {
+                if (partial) {
+                    error_setg(errp,
+                               "Unexpected end-of-file before all bytes were read");
+                } else {
+                    ret = 0;
+                }
+            }
+
+            while (fds && fd_idx) {
+                close(*fds[fd_idx - 1]);
+                fd_idx--;
+            }
+
+            if (fds) {
+                g_free(*fds);
             }
+
             goto cleanup;
         }
 
         partial = true;
         iov_discard_front(&local_iov, &nlocal_iov, len);
+
+        local_fds = NULL;
+        local_nfds = 0;
     }
 
     ret = 1;
@@ -135,20 +171,23 @@  int qio_channel_readv_all_eof(QIOChannel *ioc,
     return ret;
 }
 
-int qio_channel_readv_all(QIOChannel *ioc,
-                          const struct iovec *iov,
-                          size_t niov,
-                          Error **errp)
+int qio_channel_readv_full_all(QIOChannel *ioc,
+                               const struct iovec *iov,
+                               size_t niov,
+                               int **fds, size_t *nfds,
+                               Error **errp)
 {
-    int ret = qio_channel_readv_all_eof(ioc, iov, niov, errp);
+    int ret = qio_channel_readv_full_all_eof(ioc, iov, niov, fds, nfds, errp);
 
     if (ret == 0) {
-        ret = -1;
         error_setg(errp,
                    "Unexpected end-of-file before all bytes were read");
-    } else if (ret == 1) {
-        ret = 0;
+        return -1;
+    }
+    if (ret == 1) {
+        return 0;
     }
+
     return ret;
 }