QFileSystemEngine/Linux: fix when qt_lstatx() succeeds

When qt_lstatx() succeeds and the target is not a link, we'd erroneously
mark the file as non-existent during the pass to check qt_statx(). All
flags besides the file's modes were cleared.

This is unit-tested, but only happens on Linux kernels 4.12 or later. It
didn't happen to me because I already had this fix applied as part of a
later change relating to QSystemResult.

Task-number: QTBUG-64514
Change-Id: I938b024e38bf4aac9154fffd14f893506a1ef55b
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

1 files changed, 16 insertions, 15 deletions

diff --git a/src/corelib/io/qfilesystemengine_unix.cpp b/src/corelib/io/qfilesystemengine_unix.cpp
index d77cdc123c..4051dc43a1 100644
--- a/src/corelib/io/qfilesystemengine_unix.cpp
+++ b/src/corelib/io/qfilesystemengine_unix.cpp
@@ -918,7 +918,7 @@ bool QFileSystemEngine::fillMetaData(const QFileSystemEntry &entry, QFileSystemM
     data.entryFlags &= ~what;
 
     const QByteArray nativeFilePath = entry.nativeFilePath();
-    bool entryExists = true; // innocent until proven otherwise
+    int entryErrno = 0; // innocent until proven otherwise
 
     // first, we may try lstat(2). Possible outcomes:
     //  - success and is a symlink: filesystem entry exists, but we need stat(2)
@@ -968,7 +968,7 @@ bool QFileSystemEngine::fillMetaData(const QFileSystemEntry &entry, QFileSystemM
             }
         } else {
             // it doesn't exist
-            entryExists = false;
+            entryErrno = errno;
             data.knownFlagsMask |= QFileSystemMetaData::ExistsAttribute;
         }
 
@@ -976,8 +976,8 @@ bool QFileSystemEngine::fillMetaData(const QFileSystemEntry &entry, QFileSystemM
     }
 
     // second, we try a regular stat(2)
-    if (statResult != 0 && (what & QFileSystemMetaData::PosixStatFlags)) {
-        if (entryExists && statResult == -1) {
+    if (statResult == -1 && (what & QFileSystemMetaData::PosixStatFlags)) {
+        if (entryErrno == 0 && statResult == -1) {
             data.entryFlags &= ~QFileSystemMetaData::PosixStatFlags;
             statResult = qt_statx(nativeFilePath, &statxBuffer);
             if (statResult == -ENOSYS) {
@@ -991,7 +991,7 @@ bool QFileSystemEngine::fillMetaData(const QFileSystemEntry &entry, QFileSystemM
         }
 
         if (statResult != 0) {
-            entryExists = false;
+            entryErrno = errno;
             data.birthTime_ = 0;
             data.metadataChangeTime_ = 0;
             data.modificationTime_ = 0;
@@ -1010,13 +1010,13 @@ bool QFileSystemEngine::fillMetaData(const QFileSystemEntry &entry, QFileSystemM
     if (what & (QFileSystemMetaData::UserPermissions | QFileSystemMetaData::ExistsAttribute)) {
         // calculate user permissions
         auto checkAccess = [&](QFileSystemMetaData::MetaDataFlag flag, int mode) {
-            if (!entryExists || (what & flag) == 0)
+            if (entryErrno != 0 || (what & flag) == 0)
                 return;
             if (QT_ACCESS(nativeFilePath, mode) == 0) {
                 // access ok (and file exists)
                 data.entryFlags |= flag | QFileSystemMetaData::ExistsAttribute;
             } else if (errno != EACCES && errno != EROFS) {
-                entryExists = false;
+                entryErrno = errno;
             }
         };
 
@@ -1025,9 +1025,10 @@ bool QFileSystemEngine::fillMetaData(const QFileSystemEntry &entry, QFileSystemM
         checkAccess(QFileSystemMetaData::UserExecutePermission, X_OK);
 
         // if we still haven't found out if the file exists, try F_OK
-        if (entryExists && (data.entryFlags & QFileSystemMetaData::ExistsAttribute) == 0) {
-            entryExists = QT_ACCESS(nativeFilePath, F_OK) == 0;
-            if (entryExists)
+        if (entryErrno == 0 && (data.entryFlags & QFileSystemMetaData::ExistsAttribute) == 0) {
+            if (QT_ACCESS(nativeFilePath, F_OK) == -1)
+                entryErrno = errno;
+            else
                 data.entryFlags |= QFileSystemMetaData::ExistsAttribute;
         }
 
@@ -1037,13 +1038,13 @@ bool QFileSystemEngine::fillMetaData(const QFileSystemEntry &entry, QFileSystemM
 
 #if defined(Q_OS_DARWIN)
     if (what & QFileSystemMetaData::AliasType) {
-        if (entryExists && hasResourcePropertyFlag(data, entry, kCFURLIsAliasFileKey))
+        if (entryErrno == 0 && hasResourcePropertyFlag(data, entry, kCFURLIsAliasFileKey))
             data.entryFlags |= QFileSystemMetaData::AliasType;
         data.knownFlagsMask |= QFileSystemMetaData::AliasType;
     }
 
     if (what & QFileSystemMetaData::BundleType) {
-        if (entryExists && isPackage(data, entry))
+        if (entryErrno == 0 && isPackage(data, entry))
             data.entryFlags |= QFileSystemMetaData::BundleType;
 
         data.knownFlagsMask |= QFileSystemMetaData::BundleType;
@@ -1055,19 +1056,19 @@ bool QFileSystemEngine::fillMetaData(const QFileSystemEntry &entry, QFileSystemM
         QString fileName = entry.fileName();
         if ((fileName.size() > 0 && fileName.at(0) == QLatin1Char('.'))
 #if defined(Q_OS_DARWIN)
-                || (entryExists && hasResourcePropertyFlag(data, entry, kCFURLIsHiddenKey))
+                || (entryErrno == 0 && hasResourcePropertyFlag(data, entry, kCFURLIsHiddenKey))
 #endif
                 )
             data.entryFlags |= QFileSystemMetaData::HiddenAttribute;
         data.knownFlagsMask |= QFileSystemMetaData::HiddenAttribute;
     }
 
-    if (!entryExists) {
+    if (entryErrno != 0) {
         what &= ~QFileSystemMetaData::LinkType; // don't clear link: could be broken symlink
         data.clearFlags(what);
         return false;
     }
-    return data.hasFlags(what);
+    return true;
 }
 
 // static