Fix a bad interaction between "proxy-locking" and [http://www.sqlite.org/src/vdiff/aa6acfa8caa2ef59b4c16dfe42c4b5644da96905|aa6acfa8ca].

FossilOrigin-Name: 2a5c9e1dbf7f5f4b2081c964450a9305a4516f5b

1 files changed, 28 insertions, 18 deletions

diff --git a/src/os_unix.c b/src/os_unix.c
index 65259a756..b88cc7a8b 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -3902,7 +3902,7 @@ static int unixOpen(
   noLock = eType!=SQLITE_OPEN_MAIN_DB;
 
 #if SQLITE_PREFER_PROXY_LOCKING
-  if( zPath!=NULL && !noLock ){
+  if( zPath!=NULL && !noLock && pVfs->xOpen ){
     char *envforce = getenv("SQLITE_FORCE_PROXY_LOCKING");
     int useProxy = 0;
 
@@ -4617,33 +4617,43 @@ static int proxyGetLockPath(const char *dbPath, char *lPath, size_t maxLen){
 ** but also for freeing the memory associated with the file descriptor.
 */
 static int proxyCreateUnixFile(const char *path, unixFile **ppFile) {
-  int fd;
-  int dirfd = -1;
   unixFile *pNew;
+  int flags = SQLITE_OPEN_MAIN_DB|SQLITE_OPEN_CREATE|SQLITE_OPEN_READWRITE;
   int rc = SQLITE_OK;
   sqlite3_vfs dummyVfs;
 
-  fd = open(path, O_RDWR | O_CREAT, SQLITE_DEFAULT_FILE_PERMISSIONS);
-  if( fd<0 ){
-    return SQLITE_CANTOPEN;
-  }
-  
   pNew = (unixFile *)sqlite3_malloc(sizeof(unixFile));
-  if( pNew==NULL ){
-    rc = SQLITE_NOMEM;
-    goto end_create_proxy;
+  if( !pNew ){
+    return SQLITE_NOMEM;
   }
   memset(pNew, 0, sizeof(unixFile));
 
+  /* Call unixOpen() to open the proxy file. The flags passed to unixOpen()
+  ** suggest that the file being opened is a "main database". This is
+  ** necessary as other file types do not necessarily support locking. It
+  ** is better to use unixOpen() instead of opening the file directly with
+  ** open(), as unixOpen() sets up the various mechanisms required to
+  ** make sure a call to close() does not cause the system to discard
+  ** POSIX locks prematurely.
+  **
+  ** It is important that the xOpen member of the VFS object passed to 
+  ** unixOpen() is NULL. This tells unixOpen() may try to open a proxy-file 
+  ** for the proxy-file (creating a potential infinite loop).
+  */
   dummyVfs.pAppData = (void*)&autolockIoFinder;
-  rc = fillInUnixFile(&dummyVfs, fd, dirfd, (sqlite3_file*)pNew, path, 0, 0);
-  if( rc==SQLITE_OK ){
-    *ppFile = pNew;
-    return SQLITE_OK;
+  dummyVfs.xOpen = 0;
+  rc = unixOpen(&dummyVfs, path, (sqlite3_file *)pNew, flags, &flags);
+  if( rc==SQLITE_OK && (flags&SQLITE_OPEN_READONLY) ){
+    pNew->pMethod->xClose((sqlite3_file *)pNew);
+    rc = SQLITE_CANTOPEN;
   }
-end_create_proxy:    
-  close(fd); /* silently leak fd if error, we're already in error */
-  sqlite3_free(pNew);
+
+  if( rc!=SQLITE_OK ){
+    sqlite3_free(pNew);
+    pNew = 0;
+  }
+
+  *ppFile = pNew;
   return rc;
 }