Protect RandUint64 against EINTR.

Review URL: http://codereview.chromium.org/77022

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@14297 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 24 insertions, 3 deletions

diff --git a/base/file_util.h b/base/file_util.h
index 6728a0d..102dd4b 100644
--- a/base/file_util.h
+++ b/base/file_util.h
@@ -222,6 +222,13 @@ bool ReadFileToString(const FilePath& path, std::string* contents);
 // Deprecated version.
 bool ReadFileToString(const std::wstring& path, std::string* contents);
 
+#if defined(OS_POSIX)
+// Read exactly |bytes| bytes from file descriptor |fd|, storing the result
+// in |buffer|. This function is protected against EINTR and partial reads.
+// Returns true iff |bytes| bytes have been successfuly read from |fd|.
+bool ReadFromFD(int fd, char* buffer, size_t bytes);
+#endif  // defined(OS_POSIX)
+
 #if defined(OS_WIN)
 // Resolve Windows shortcut (.LNK file)
 // Argument path specifies a valid LNK file. On success, return true and put
diff --git a/base/file_util_posix.cc b/base/file_util_posix.cc
index 6a36c62..f571c5e 100644
--- a/base/file_util_posix.cc
+++ b/base/file_util_posix.cc
@@ -316,6 +316,18 @@ bool GetFileCreationLocalTime(const std::string& filename,
 }
 #endif
 
+bool ReadFromFD(int fd, char* buffer, size_t bytes) {
+  size_t total_read = 0;
+  while (total_read < bytes) {
+    ssize_t bytes_read = read(fd, buffer + total_read, bytes - total_read);
+    if (bytes_read > 0)
+      total_read += bytes_read;
+    else if (errno != EINTR || bytes_read == 0)
+      break;
+  }
+  return total_read == bytes;
+}
+
 // Creates and opens a temporary file in |directory|, returning the
 // file descriptor.  |path| is set to the temporary file path.
 // Note TODO(erikkay) comment in header for BlahFileName() calls; the
diff --git a/base/rand_util_posix.cc b/base/rand_util_posix.cc
index e0b4257..b4f3ac2 100644
--- a/base/rand_util_posix.cc
+++ b/base/rand_util_posix.cc
@@ -5,9 +5,9 @@
 #include "base/rand_util.h"
 
 #include <fcntl.h>
-#include <sys/stat.h>
 #include <unistd.h>
 
+#include "base/file_util.h"
 #include "base/logging.h"
 
 namespace base {
@@ -17,8 +17,10 @@ uint64 RandUint64() {
 
   int urandom_fd = open("/dev/urandom", O_RDONLY);
   CHECK(urandom_fd >= 0);
-  ssize_t bytes_read = read(urandom_fd, &number, sizeof(number));
-  CHECK(bytes_read == sizeof(number));
+  bool success = file_util::ReadFromFD(urandom_fd,
+                                       reinterpret_cast<char*>(&number),
+                                       sizeof(number));
+  CHECK(success);
   close(urandom_fd);
 
   return number;