Add locking around ZIP seeking

Since we switched to seeking to the LFH to verify its existence instead
of a huge mmap of the file, we have to guarantee that another seek
doesn't happen before we finish our read on the LFH.

Change-Id: If8135d9cb6f2f5cc4db734eafa4f6b5f6269c62a

2 files changed, 23 insertions, 12 deletions

diff --git a/include/utils/ZipFileRO.h b/include/utils/ZipFileRO.h
index 97d31f4db4f3..9668bdeef55b 100644
--- a/include/utils/ZipFileRO.h
+++ b/include/utils/ZipFileRO.h
@@ -24,8 +24,9 @@
 #ifndef __LIBS_ZIPFILERO_H
 #define __LIBS_ZIPFILERO_H
 
-#include "Errors.h"
-#include "FileMap.h"
+#include <utils/Errors.h>
+#include <utils/FileMap.h>
+#include <utils/threads.h>
 
 #include <stdio.h>
 #include <stdlib.h>
@@ -211,6 +212,9 @@ private:
     /* open Zip archive */
     int         mFd;
 
+    /* Lock for handling the file descriptor (seeks, etc) */
+    mutable Mutex mFdLock;
+
     /* zip file name */
     char*       mFileName;
 
diff --git a/libs/utils/ZipFileRO.cpp b/libs/utils/ZipFileRO.cpp
index 2d53136c1484..59809c2f94d6 100644
--- a/libs/utils/ZipFileRO.cpp
+++ b/libs/utils/ZipFileRO.cpp
@@ -22,6 +22,7 @@
 #include <utils/ZipFileRO.h>
 #include <utils/Log.h>
 #include <utils/misc.h>
+#include <utils/threads.h>
 
 #include <zlib.h>
 
@@ -195,7 +196,7 @@ bool ZipFileRO::mapCentralDirectory(void)
             free(scanBuf);
             return false;
         } else if (header != kLFHSignature) {
-            LOGV("Not a Zip archive (found 0x%08x)\n", val);
+            LOGV("Not a Zip archive (found 0x%08x)\n", header);
             free(scanBuf);
             return false;
         }
@@ -496,15 +497,21 @@ bool ZipFileRO::getEntryInfo(ZipEntryRO entry, int* pMethod, size_t* pUncompLen,
         }
 
         unsigned char lfhBuf[kLFHLen];
-        if (lseek(mFd, localHdrOffset, SEEK_SET) != localHdrOffset) {
-            LOGW("failed seeking to lfh at offset %ld\n", localHdrOffset);
-            return false;
-        }
-        ssize_t actual =
-            TEMP_FAILURE_RETRY(read(mFd, lfhBuf, sizeof(lfhBuf)));
-        if (actual != sizeof(lfhBuf)) {
-            LOGW("failed reading lfh from offset %ld\n", localHdrOffset);
-            return false;
+
+        {
+            AutoMutex _l(mFdLock);
+
+            if (lseek(mFd, localHdrOffset, SEEK_SET) != localHdrOffset) {
+                LOGW("failed seeking to lfh at offset %ld\n", localHdrOffset);
+                return false;
+            }
+
+            ssize_t actual =
+                TEMP_FAILURE_RETRY(read(mFd, lfhBuf, sizeof(lfhBuf)));
+            if (actual != sizeof(lfhBuf)) {
+                LOGW("failed reading lfh from offset %ld\n", localHdrOffset);
+                return false;
+            }
         }
 
         if (get4LE(lfhBuf) != kLFHSignature) {