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.

(Land attempt two: first in r39446, reverted in r39448)

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@39899 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 22 insertions, 0 deletions

diff --git a/base/platform_file.h b/base/platform_file.h
index 0dbf4e4..46ff0cc 100644
--- a/base/platform_file.h
+++ b/base/platform_file.h
@@ -6,6 +6,8 @@
 #define BASE_PLATFORM_FILE_H_
 
 #include "build/build_config.h"
+#include "base/basictypes.h"
+
 #if defined(OS_WIN)
 #include <windows.h>
 #endif
@@ -53,6 +55,10 @@ 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);
+
 }  // namespace base
 
 #endif  // BASE_PLATFORM_FILE_H_
diff --git a/base/platform_file_posix.cc b/base/platform_file_posix.cc
index 46039b9..bfd40e9 100644
--- a/base/platform_file_posix.cc
+++ b/base/platform_file_posix.cc
@@ -77,4 +77,12 @@ bool ClosePlatformFile(PlatformFile file) {
   return close(file);
 }
 
+bool GetPlatformFileSize(PlatformFile file, uint64* out_size) {
+  struct stat st;
+  if (fstat(file, &st))
+    return false;
+  *out_size = st.st_size;
+  return true;
+}
+
 }  // namespace base
diff --git a/base/platform_file_win.cc b/base/platform_file_win.cc
index 1143487..ccaee1e 100644
--- a/base/platform_file_win.cc
+++ b/base/platform_file_win.cc
@@ -75,4 +75,12 @@ bool ClosePlatformFile(PlatformFile file) {
   return (CloseHandle(file) == 0);
 }
 
+bool GetPlatformFileSize(PlatformFile file, uint64* out_size) {
+  LARGE_INTEGER size;
+  if (!GetFileSizeEx(file, &size))
+    return false;
+  *out_size = size.QuadPart;
+  return true;
+}
+
 }  // namespace disk_cache