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QFileSystemEngine::canonicalName (Unix): clean up control-flow

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When passing a nullptr to realpath, it will allocate memory. That memory
has to be freed (with free) later to avoid a leak, which we so far
didn't.
This patch ensures that we always clean up the memory by using a
unique_ptr. As a drive-by, clean up the control-flow:
- Always pass either the stack buffer or nullptr to realpath.
- Rely on realpath returning nullptr in the error case.
Lastly, fix a few coding-style issues.

Change-Id: Ia906df77324020c267b087ec52a9a6c47aaa2a59
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
This commit is contained in:
Fabian Kosmale 2022-02-14 10:29:24 +01:00
parent e1b76e68d0
commit 06e45cbd6a
1 changed files with 23 additions and 20 deletions
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43
src/corelib/io/qfilesystemengine_unix.cpp
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@ -58,6 +58,8 @@
#include <stdio.h>
#include <errno.h>
#include <memory> // for std::unique_ptr
#if __has_include(<paths.h>)
# include <paths.h>
#endif
@ -687,39 +689,40 @@ QFileSystemEntry QFileSystemEngine::canonicalName(const QFileSystemEntry &entry,
return QFileSystemEntry(slowCanonicalized(absoluteName(entry).filePath()));
#else
# if defined(Q_OS_DARWIN) || defined(Q_OS_ANDROID) || _POSIX_VERSION < 200801L
char stack_result[PATH_MAX+1];
// used to store the result of realpath in case where realpath cannot allocate itself
char stack_result[PATH_MAX + 1];
#else
// enables unconditionally passing stack_result below
std::nullptr_t stack_result = nullptr;
# endif
char *resolved_name = nullptr;
auto resolved_path_deleter = [&](char *ptr) {
// frees resolved_name if it was allocated by realpath
# if defined(Q_OS_DARWIN) || defined(Q_OS_ANDROID) || _POSIX_VERSION < 200801L
// ptr is either null, or points to stack_result
Q_ASSERT(!ptr || ptr == stack_result);
return;
#else
free(ptr);
# endif
};
std::unique_ptr<char, decltype (resolved_path_deleter)> resolved_name {nullptr, resolved_path_deleter};
# if defined(Q_OS_DARWIN) || defined(Q_OS_ANDROID)
// On some Android and macOS versions, realpath() will return a path even if
// it does not exist. To work around this, we check existence in advance.
if (!data.hasFlags(QFileSystemMetaData::ExistsAttribute))
fillMetaData(entry, data, QFileSystemMetaData::ExistsAttribute);
if (!data.exists()) {
if (!data.exists())
errno = ENOENT;
} else {
resolved_name = stack_result;
}
if (resolved_name && realpath(entry.nativeFilePath().constData(), resolved_name) == nullptr)
resolved_name = nullptr;
else
resolved_name.reset(realpath(entry.nativeFilePath().constData(), stack_result));
# else
# if _POSIX_VERSION >= 200801L // ask realpath to allocate memory
resolved_name = realpath(entry.nativeFilePath().constData(), nullptr);
# else
resolved_name = stack_result;
if (realpath(entry.nativeFilePath().constData(), resolved_name) == nullptr)
resolved_name = nullptr;
# endif
resolved_name.reset(realpath(entry.nativeFilePath().constData(), stack_result));
# endif
if (resolved_name) {
data.knownFlagsMask |= QFileSystemMetaData::ExistsAttribute;
data.entryFlags |= QFileSystemMetaData::ExistsAttribute;
QString canonicalPath = QDir::cleanPath(QFile::decodeName(resolved_name));
# if defined(Q_OS_DARWIN) || defined(Q_OS_ANDROID) || _POSIX_VERSION < 200801L
if (resolved_name != stack_result)
free(resolved_name);
# endif
QString canonicalPath = QDir::cleanPath(QFile::decodeName(resolved_name.get()));
return QFileSystemEntry(canonicalPath);
} else if (errno == ENOENT || errno == ENOTDIR) { // file doesn't exist
data.knownFlagsMask |= QFileSystemMetaData::ExistsAttribute;