Re: [BUG 2.4] NFS unlocking operation accesses invalid file struct

[Trond Myklebust]

>>>>> " " == Akinobu Mita <mita@xxxxxxxxxxxxxxxx> writes:


     > Does anyone have a idea of how to fix it ?

Yes. I posted a patch about a week or 2 ago. The original patch can be
found on

  http://www.fys.uio.no/~trondmy/src/Linux-2.4.x/2.4.23-rc1/linux-2.4.23-01-posix_race.dif

However, I now believe the real problem here is that
locks_remove_posix() should also be checking the pid (as is done in
all the other POSIX locking checks by calling locks_same_owner()).

It is wrong for locks_remove_posix() to be deleting locks that don't
belong to this pid... Note: this bug exists in 2.6.x. too, although
there it does not cause an Oops...

Cheers,
  Trond

--- linux-2.4.23-rc1/fs/locks.c.orig	2003-11-16 19:30:53.000000000 -0500
+++ linux-2.4.23-rc1/fs/locks.c	2003-11-25 19:34:02.000000000 -0500
@@ -1746,7 +1746,8 @@
 	lock_kernel();
 	before = &inode->i_flock;
 	while ((fl = *before) != NULL) {
-		if ((fl->fl_flags & FL_POSIX) && fl->fl_owner == owner) {
+		if ((fl->fl_flags & FL_POSIX) && fl->fl_owner == owner &&
+				fl->fl_pid == current->pid) {
 			locks_unlock_delete(before);
 			before = &inode->i_flock;
 			continue;
-
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