From e659b80f365c68aafa7c2f25960ae782a786b6e1 Mon Sep 17 00:00:00 2001
From: Uli Schlachter <psychon@znc.in>
Date: Sun, 8 Jan 2017 15:23:18 +0100
Subject: [PATCH] Refuse attempts to resize clients to invalid size

X11 does not allow to resize a window to size 0x0. Also, there are some
possibilities of integer overflows in our case. We tried to handle this
already, but there was a loop-hole: If the too-small-value is only
produced after applying size hints, then this was not caught.

Fix this by applying size hints before checking if the resulting size is
valid. However, this means some check needs to be duplicated to handle
the possibility of integer underflows while applying size hints.

Helps-with: https://github.com/awesomeWM/awesome/issues/1340
Signed-off-by: Uli Schlachter <psychon@znc.in>
---
 objects/client.c      | 14 +++++++++++---
 tests/test-resize.lua | 31 +++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 3 deletions(-)

diff --git a/objects/client.c b/objects/client.c
index ac3c9cc2b..d347d0842 100644
--- a/objects/client.c
+++ b/objects/client.c
@@ -1678,6 +1678,17 @@ client_resize(client_t *c, area_t geometry, bool honor_hints)
     if(geometry.y + geometry.height < 0)
         geometry.y = 0;
 
+    if (honor_hints) {
+        /* We could get integer underflows in client_remove_titlebar_geometry()
+         * without these checks here.
+         */
+        if(geometry.width < c->titlebar[CLIENT_TITLEBAR_LEFT].size + c->titlebar[CLIENT_TITLEBAR_RIGHT].size)
+            return false;
+        if(geometry.height < c->titlebar[CLIENT_TITLEBAR_TOP].size + c->titlebar[CLIENT_TITLEBAR_BOTTOM].size)
+            return false;
+        geometry = client_apply_size_hints(c, geometry);
+    }
+
     if(geometry.width < c->titlebar[CLIENT_TITLEBAR_LEFT].size + c->titlebar[CLIENT_TITLEBAR_RIGHT].size)
         return false;
     if(geometry.height < c->titlebar[CLIENT_TITLEBAR_TOP].size + c->titlebar[CLIENT_TITLEBAR_BOTTOM].size)
@@ -1686,9 +1697,6 @@ client_resize(client_t *c, area_t geometry, bool honor_hints)
     if(geometry.width == 0 || geometry.height == 0)
         return false;
 
-    if (honor_hints)
-        geometry = client_apply_size_hints(c, geometry);
-
     if(!AREA_EQUAL(c->geometry, geometry))
     {
         client_resize_do(c, geometry);
diff --git a/tests/test-resize.lua b/tests/test-resize.lua
index 298323efb..67a75d9c8 100644
--- a/tests/test-resize.lua
+++ b/tests/test-resize.lua
@@ -439,6 +439,37 @@ table.insert(steps, function()
     return true
 end)
 
+table.insert(steps, function()
+    for _, c in pairs(client.get()) do
+        c:kill()
+    end
+    if #client.get() == 0 then
+        test_client(nil, nil, nil, nil, true)
+        return true
+    end
+end)
+
+table.insert(steps, function()
+    if #client.get() ~= 1 then
+        return
+    end
+
+    local c = client.get()[1]
+    local geo = c:geometry()
+    local hints = c.size_hints
+    assert(hints.height_inc == 200)
+    assert(hints.width_inc == 200)
+    assert(c:apply_size_hints(1, 1) == 0)
+
+    c:geometry { width = 1, height = 50 }
+
+    -- The above should be rejected, because it would make us resize the
+    -- window size 0x0.
+    assert(c:geometry().width == geo.width)
+    assert(c:geometry().height == geo.height)
+    return true
+end)
+
 require("_runner").run_steps(steps)
 
 -- vim: filetype=lua:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:textwidth=80