[PATCH xserver] Xext/shm: Refuse to work for remote clients

[Alexander Volkov]

Avoid access to System V shared memory segment on the X server side
for clients forwarded via SSH. Also prevent them from hanging while
waiting for the reply from the ShmCreateSegment request.

v2: Allow ShmQueryVersion request even for remote clients

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=11080
Signed-off-by: Alexander Volkov <a.volkov at rusbitech.ru>
---
 Xext/shm.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/Xext/shm.c b/Xext/shm.c
index fc8441c43..896a966e3 100644
--- a/Xext/shm.c
+++ b/Xext/shm.c
@@ -1302,9 +1302,14 @@ static int
 ProcShmDispatch(ClientPtr client)
 {
     REQUEST(xReq);
-    switch (stuff->data) {
-    case X_ShmQueryVersion:
+
+    if (stuff->data == X_ShmQueryVersion)
         return ProcShmQueryVersion(client);
+
+    if (!client->local)
+        return BadRequest;
+
+    switch (stuff->data) {
     case X_ShmAttach:
         return ProcShmAttach(client);
     case X_ShmDetach:
@@ -1461,9 +1466,14 @@ static int _X_COLD
 SProcShmDispatch(ClientPtr client)
 {
     REQUEST(xReq);
-    switch (stuff->data) {
-    case X_ShmQueryVersion:
+
+    if (stuff->data == X_ShmQueryVersion)
         return SProcShmQueryVersion(client);
+
+    if (!client->local)
+        return BadRequest;
+
+    switch (stuff->data) {
     case X_ShmAttach:
         return SProcShmAttach(client);
     case X_ShmDetach:
-- 
2.17.0