Fix the case where the browser livelocks if we cannot open a file.

If one tries to upload a file that one doesn't have read access to,
the browser livelocks. It tries to read from the file, gets nothing
but spins forever because it knows that it hasn't finished reading.

To address this, firstly we add a check at stat() time to make sure
that we can read the file. However, this doesn't take care of the case
where the access() call was incorrect, or the permissions have changed
under us. In this case, we replace the missing file with NULs.

http://codereview.chromium.org/541022
BUG=30850
TEST=Try to upload a file that isn't readable (i.e. /etc/shadow). The resulting upload should be a 0 byte file.

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@39446 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 37 insertions, 0 deletions

diff --git a/base/platform_file.h b/base/platform_file.h
index 0dbf4e4..4ab1ace 100644
--- a/base/platform_file.h
+++ b/base/platform_file.h
@@ -12,6 +12,8 @@
 
 #include <string>
 
+#include "base/ref_counted.h"
+
 class FilePath;
 
 namespace base {
@@ -53,6 +55,41 @@ PlatformFile CreatePlatformFile(const std::wstring& name,
 // Closes a file handle
 bool ClosePlatformFile(PlatformFile file);
 
+// Get the length of an underlying file. Returns false on error. Otherwise
+// *size is set to the length of the file, in bytes.
+bool GetPlatformFileSize(PlatformFile file, uint64* size);
+
+// This is a reference counted PlatformFile. When the ref count drops to zero,
+// the file handle is closed. See the comments in base/ref_counted.h for
+// details on how to use it.
+class RefCountedPlatformFile :
+    public base::RefCountedThreadSafe<RefCountedPlatformFile> {
+ public:
+  RefCountedPlatformFile(PlatformFile f) : file_(f) { }
+
+  ~RefCountedPlatformFile() {
+    if (file_ != kInvalidPlatformFileValue) {
+      ClosePlatformFile(file_);
+      file_ = kInvalidPlatformFileValue;
+    }
+  }
+
+  PlatformFile get() const {
+    return file_;
+  }
+
+  PlatformFile release() {
+    PlatformFile f = file_;
+    file_ = kInvalidPlatformFileValue;
+    return f;
+  }
+
+ private:
+  PlatformFile file_;
+
+  DISALLOW_COPY_AND_ASSIGN(RefCountedPlatformFile);
+};
+
 }  // namespace base
 
 #endif  // BASE_PLATFORM_FILE_H_