File 0286-9pfs-allocate-space-for-guest-origi.patch of Package qemu.3557

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File 0286-9pfs-allocate-space-for-guest-origi.patch of Package qemu.3557

From 4e51580ec335ae9e9848567e9b9026a183c336af Mon Sep 17 00:00:00 2001
From: Li Qiang <liqiang6-s@360.cn>
Date: Mon, 17 Oct 2016 14:13:58 +0200
Subject: [PATCH] 9pfs: allocate space for guest originated empty strings

If a guest sends an empty string paramater to any 9P operation, the current
code unmarshals it into a V9fsString equal to { .size = 0, .data = NULL }.

This is unfortunate because it can cause NULL pointer dereference to happen
at various locations in the 9pfs code. And we don't want to check str->data
everywhere we pass it to strcmp() or any other function which expects a
dereferenceable pointer.

This patch enforces the allocation of genuine C empty strings instead, so
callers don't have to bother.

Out of all v9fs_iov_vunmarshal() users, only v9fs_xattrwalk() checks if
the returned string is empty. It now uses v9fs_string_size() since
name.data cannot be NULL anymore.

Signed-off-by: Li Qiang <liqiang6-s@360.cn>
[groug, rewritten title and changelog,
 fix empty string check in v9fs_xattrwalk()]
Signed-off-by: Greg Kurz <groug@kaod.org>
(cherry picked from commit ba42ebb863ab7d40adc79298422ed9596df8f73a)
[BR: CVE-2016-8578 BSC#1003894]
Signed-off-by: Bruce Rogers <brogers@suse.com>
---
 fsdev/virtio-9p-marshal.c | 2 +-
 hw/9pfs/virtio-9p.c       | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/fsdev/virtio-9p-marshal.c b/fsdev/virtio-9p-marshal.c
index 20f308b..c694695 100644
--- a/fsdev/virtio-9p-marshal.c
+++ b/fsdev/virtio-9p-marshal.c
@@ -166,7 +166,7 @@ ssize_t v9fs_unmarshal(struct iovec *out_sg, int out_num, size_t offset,
                 str->data = g_malloc(str->size + 1);
                 copied = v9fs_unpack(str->data, out_sg, out_num, offset,
                                      str->size);
-                if (copied > 0) {
+                if (copied >= 0) {
                     str->data[str->size] = 0;
                 } else {
                     v9fs_string_free(str);
diff --git a/hw/9pfs/virtio-9p.c b/hw/9pfs/virtio-9p.c
index ef47d3a..8bc228d 100644
--- a/hw/9pfs/virtio-9p.c
+++ b/hw/9pfs/virtio-9p.c
@@ -3023,7 +3023,7 @@ static void v9fs_xattrwalk(void *opaque)
         goto out;
     }
     v9fs_path_copy(&xattr_fidp->path, &file_fidp->path);
-    if (name.data == NULL) {
+    if (!v9fs_string_size(&name)) {
         /*
          * listxattr request. Get the size first
          */

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File 0286-9pfs-allocate-space-for-guest-origi.patch of Package qemu.3557

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