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-rw-r--r--source3/locking/locking.c71
1 files changed, 56 insertions, 15 deletions
diff --git a/source3/locking/locking.c b/source3/locking/locking.c
index 6e321d0626..639bc7be0b 100644
--- a/source3/locking/locking.c
+++ b/source3/locking/locking.c
@@ -25,6 +25,10 @@
May 1997. Jeremy Allison (jallison@whistle.com). Modified share mode
locking to deal with multiple share modes per open file.
+
+ September 1997. Jeremy Allison (jallison@whistle.com). Added oplock
+ support.
+
*/
#include "includes.h"
@@ -726,13 +730,60 @@ BOOL lock_share_entry(int cnum, uint32 dev, uint32 inode, share_lock_token *ptok
{
int old_umask;
+ BOOL gotlock = False;
unbecome_user();
old_umask = umask(0);
+
+ /*
+ * There was a race condition in the original slow share mode code.
+ * A smbd could open a share mode file, and before getting
+ * the lock, another smbd could delete the last entry for
+ * the share mode file and delete the file entry from the
+ * directory. Thus this smbd would be left with a locked
+ * share mode fd attached to a file that no longer had a
+ * directory entry. Thus another smbd would think that
+ * there were no outstanding opens on the file. To fix
+ * this we now check we can do a stat() call on the filename
+ * before allowing the lock to proceed, and back out completely
+ * and try the open again if we cannot.
+ * Jeremy Allison (jallison@whistle.com).
+ */
+
+ do
+ {
+ struct stat dummy_stat;
+
#ifdef SECURE_SHARE_MODES
- fd = (share_lock_token)open(fname,O_RDWR|O_CREAT,0600);
+ fd = (share_lock_token)open(fname,O_RDWR|O_CREAT,0600);
#else /* SECURE_SHARE_MODES */
- fd = (share_lock_token)open(fname,O_RDWR|O_CREAT,0666);
+ fd = (share_lock_token)open(fname,O_RDWR|O_CREAT,0666);
#endif /* SECURE_SHARE_MODES */
+
+ /* At this point we have an open fd to the share mode file.
+ Lock the first byte exclusively to signify a lock. */
+ if(fcntl_lock(fd, F_SETLKW, 0, 1, F_WRLCK) == False)
+ {
+ DEBUG(0,("ERROR lock_share_entry: fcntl_lock on file %s failed with %s\n",
+ fname, strerror(errno)));
+ close(fd);
+ return False;
+ }
+
+ /*
+ * If we cannot stat the filename, the file was deleted between
+ * the open and the lock call. Back out and try again.
+ */
+
+ if(stat(fname, &dummy_stat)!=0)
+ {
+ DEBUG(2,("lock_share_entry: Re-issuing open on %s to fix race. Error was %s\n",
+ fname, strerror(errno)));
+ close(fd);
+ }
+ else
+ gotlock = True;
+ } while(!gotlock);
+
umask(old_umask);
if(!become_user(cnum,Connections[cnum].vuid))
{
@@ -750,18 +801,8 @@ BOOL lock_share_entry(int cnum, uint32 dev, uint32 inode, share_lock_token *ptok
}
}
- /* At this point we have an open fd to the share mode file.
- Lock the first byte exclusively to signify a lock. */
- if(fcntl_lock(fd, F_SETLKW, 0, 1, F_WRLCK) == False)
- {
- DEBUG(0,("ERROR lock_share_entry: fcntl_lock failed with %s\n",
- strerror(errno)));
- close(fd);
- return False;
- }
-
- *ptok = (share_lock_token)fd;
- return True;
+ *ptok = (share_lock_token)fd;
+ return True;
}
/*******************************************************************
@@ -781,7 +822,7 @@ BOOL unlock_share_entry(int cnum, uint32 dev, uint32 inode, share_lock_token tok
ret = False;
}
- close((int)token);
+ close(fd);
return ret;
}