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Change the unix VFS to always allocate shared-memory using a file in the

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same directory as the database.  Otherwise, a chroot might cause different
processes to use different shared memory files resulting in database
corruption.

FossilOrigin-Name: 2241788bc85fbc48e9cfecb95fe0a858338e37cb
This commit is contained in:
drh
2010-06-19 15:10:09 +00:00
parent be5c10477c
commit 7234c6d6f6
3 changed files with 42 additions and 46 deletions
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62
src/os_unix.c
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@@ -3274,19 +3274,21 @@ static void unixShmPurge(unixFile *pFd){
}
}
/* Forward reference */
static const char *unixTempFileDir(int);
/*
** Open a shared-memory area. This particular implementation uses
** mmapped files.
** Open a shared-memory area associated with open database file fd.
** This particular implementation uses mmapped files.
**
** zName is a filename used to identify the shared-memory area. The
** implementation does not (and perhaps should not) use this name
** directly, but rather use it as a template for finding an appropriate
** name for the shared-memory storage. In this implementation, the
** string "-index" is appended to zName and used as the name of the
** mmapped file.
** The file used to implement shared-memory is in the same directory
** as the open database file and has the same name as the open database
** file with the "-shm" suffix added. For example, if the database file
** is "/home/user1/config.db" then the file that is created and mmapped
** for shared memory will be called "/home/user1/config.db-shm". We
** experimented with using files in /dev/tmp or an some other tmpfs mount.
** But if a file in a different directory from the database file is used,
** then differing access permissions or a chroot() might cause two different
** processes on the same database to end up using different files for
** shared memory - meaning that their memory would not really be shared -
** resulting in database corruption.
**
** When opening a new shared-memory file, if no other instances of that
** file are currently open, in this process or in other processes, then
@@ -3300,8 +3302,8 @@ static int unixShmOpen(
int rc; /* Result code */
struct unixFile *pDbFd; /* Underlying database file */
unixInodeInfo *pInode; /* The inode of fd */
const char *zTempDir; /* Directory for temporary files */
int nTempDir; /* Size of the zTempDir string */
char *zShmFilename; /* Name of the file used for SHM */
int nShmFilename; /* Size of the SHM filename in bytes */
/* Allocate space for the new sqlite3_shm object.
*/
@@ -3318,23 +3320,15 @@ static int unixShmOpen(
pInode = pDbFd->pInode;
pShmNode = pInode->pShmNode;
if( pShmNode==0 ){
zTempDir = unixTempFileDir(1);
if( zTempDir==0 ){
unixLeaveMutex();
sqlite3_free(p);
return SQLITE_CANTOPEN_NOTEMPDIR;
}
nTempDir = strlen(zTempDir);
pShmNode = sqlite3_malloc( sizeof(*pShmNode) + nTempDir + 50 );
nShmFilename = 5 + (int)strlen(pDbFd->zPath);
pShmNode = sqlite3_malloc( sizeof(*pShmNode) + nShmFilename );
if( pShmNode==0 ){
rc = SQLITE_NOMEM;
goto shm_open_err;
}
memset(pShmNode, 0, sizeof(*pShmNode));
pShmNode->zFilename = (char*)&pShmNode[1];
sqlite3_snprintf(nTempDir+50, pShmNode->zFilename,
"%s/sqlite-wi-%x-%x", zTempDir,
(u32)pInode->fileId.dev, (u32)pInode->fileId.ino);
zShmFilename = pShmNode->zFilename = (char*)&pShmNode[1];
sqlite3_snprintf(nShmFilename, zShmFilename, "%s-shm", pDbFd->zPath);
pShmNode->h = -1;
pDbFd->pInode->pShmNode = pShmNode;
pShmNode->pInode = pDbFd->pInode;
@@ -3344,7 +3338,7 @@ static int unixShmOpen(
goto shm_open_err;
}
pShmNode->h = open(pShmNode->zFilename, O_RDWR|O_CREAT, 0664);
pShmNode->h = open(zShmFilename, O_RDWR|O_CREAT, 0664);
if( pShmNode->h<0 ){
rc = SQLITE_CANTOPEN_BKPT;
goto shm_open_err;
@@ -4157,7 +4151,7 @@ static int openDirectory(const char *zFilename, int *pFd){
** Return the name of a directory in which to put temporary files.
** If no suitable temporary file directory can be found, return NULL.
*/
static const char *unixTempFileDir(int allowShm){
static const char *unixTempFileDir(void){
static const char *azDirs[] = {
0,
0,
@@ -4172,19 +4166,11 @@ static const char *unixTempFileDir(int allowShm){
azDirs[0] = sqlite3_temp_directory;
if( !azDirs[1] ) azDirs[1] = getenv("TMPDIR");
if( allowShm ){
zDir = "/dev/shm";
i = 2; /* Skip the app-defined temp locations for shared-memory */
}else{
zDir = azDirs[0];
i = 1;
}
for(; i<sizeof(azDirs)/sizeof(azDirs[0]); zDir=azDirs[i++]){
for(i==0; i<sizeof(azDirs)/sizeof(azDirs[0]); zDir=azDirs[i++]){
if( zDir==0 ) continue;
if( stat(zDir, &buf) ) continue;
if( !S_ISDIR(buf.st_mode) ) continue;
if( !allowShm && access(zDir, 07) ) continue;
if( access(zDir, 07) ) continue;
break;
}
return zDir;
@@ -4209,7 +4195,7 @@ static int unixGetTempname(int nBuf, char *zBuf){
*/
SimulateIOError( return SQLITE_IOERR );
zDir = unixTempFileDir(0);
zDir = unixTempFileDir();
if( zDir==0 ) zDir = ".";
/* Check that the output buffer is large enough for the temporary file