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Improvements to the robust_open() logic in the unix VFS so that if an attempt

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is made to open a repository on file descriptors 0, 1, or 2, and blocking
that file descriptor by opening it on /dev/null fails, then the open will
fail.

FossilOrigin-Name: d9c018f8155ab48df8e0e02519bba50588fe49fc
This commit is contained in:
drh
2013-08-30 06:20:23 +00:00
parent 00ea0e1133
commit 5128d009c6
3 changed files with 19 additions and 34 deletions
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39
src/os_unix.c
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@@ -551,31 +551,6 @@ static const char *unixNextSystemCall(sqlite3_vfs *p, const char *zName){
return 0;
}
/*
** If fd is a file descriptor that would be dangerous to use for an
** ordinary file, the close it, reopen it as /dev/null to get it out
** of the way, then return true.
**
** If fd is safe, return 0.
**
** It is dangerous to have a database file open of file descriptors 1 or
** 2 because those normally mean standard output and standard error. Other
** components of the system might write directly to those file descriptors
** and overwrite parts of the database file. Something like this happened
** on 2013-08-29 to the canonical Fossil repository when some error caused
** the database file to be opened on file descriptor 2 and later an assert()
** fired and wrote error message text into file descriptor 2, corrupting
** the repository.
*/
static int isReservedFd(int fd, const char *z, int f, int m){
if( fd<0 || fd>2 ) return 0;
sqlite3_log(SQLITE_WARNING,
"attempt to open \"%s\" as file descriptor %d", z, fd);
osClose(fd);
(void)osOpen("/dev/null",f,m);
return 1;
}
/*
** Invoke open(). Do so multiple times, until it either succeeds or
** fails for some reason other than EINTR.
@@ -596,13 +571,23 @@ static int isReservedFd(int fd, const char *z, int f, int m){
static int robust_open(const char *z, int f, mode_t m){
int fd;
mode_t m2 = m ? m : SQLITE_DEFAULT_FILE_PERMISSIONS;
do{
while(1){
#if defined(O_CLOEXEC)
fd = osOpen(z,f|O_CLOEXEC,m2);
#else
fd = osOpen(z,f,m2);
#endif
}while( (fd<0 && errno==EINTR) || isReservedFd(fd,z,f,m2) );
if( fd<0 ){
if( errno==EINTR ) continue;
break;
}
if( fd>2 ) break;
osClose(fd);
sqlite3_log(SQLITE_WARNING,
"attempt to open \"%s\" as file descriptor %d", z, fd);
fd = -1;
if( osOpen("/dev/null", f, m)<0 ) break;
}
if( fd>=0 ){
if( m!=0 ){
struct stat statbuf;