kio/0001-PreviewJob-Create-a-larger-SHM-when-necessary.patch

From bc02b2528c97eab0961b3ad608a4914d3ce4b46c Mon Sep 17 00:00:00 2001
From: Fabian Vogt <fabian@ritter-vogt.de>
Date: Tue, 4 May 2021 22:22:53 +0200
Subject: [PATCH] PreviewJob: Create a larger SHM when necessary

It's possible that during the lifetime of a PreviewJob thumbnails with
different sizes are created. The SHM was created to match the size of the first
(non-empty) thumbnail, so any larger ones after that would reuse the SHM with
insufficient size.

BUG: 430862
---
 src/widgets/previewjob.cpp | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/src/widgets/previewjob.cpp b/src/widgets/previewjob.cpp
index d30f71cf..4f71c1c7 100644
--- a/src/widgets/previewjob.cpp
+++ b/src/widgets/previewjob.cpp
@@ -136,6 +136,8 @@ public:
     int shmid;
     // And the data area
     uchar *shmaddr;
+    // Size of the shm segment
+    size_t shmsize;
     // Root of thumbnail cache
     QString thumbRoot;
     // List of encrypted mount points for checking if we should save thumbnail
@@ -733,17 +735,19 @@ void PreviewJobPrivate::createThumbnail(const QString &pixPath)
     }
 
 #if WITH_SHM
-    if (shmid == -1) {
+    size_t requiredSize = thumb_width * devicePixelRatio * thumb_height * devicePixelRatio * 4;
+    if (shmid == -1 || shmsize < requiredSize) {
         if (shmaddr) {
             // clean previous shared memory segment
             shmdt((char *)shmaddr);
-            shmctl(shmid, IPC_RMID, nullptr);
             shmaddr = nullptr;
+            shmctl(shmid, IPC_RMID, nullptr);
+            shmid = -1;
         }
-        auto size = thumb_width * thumb_height;
-        if (size > 0) {
-            shmid = shmget(IPC_PRIVATE, size * 4 * devicePixelRatio * devicePixelRatio, IPC_CREAT | 0600);
+        if (requiredSize > 0) {
+            shmid = shmget(IPC_PRIVATE, requiredSize, IPC_CREAT | 0600);
             if (shmid != -1) {
+                shmsize = requiredSize;
                 shmaddr = (uchar *)(shmat(shmid, nullptr, SHM_RDONLY));
                 if (shmaddr == (uchar *)-1) {
                     shmctl(shmid, IPC_RMID, nullptr);
-- 
2.25.1