locks,lockd: fix race in nlmsvc_testlock
posix_test_lock() returns a pointer to a struct file_lock which is unprotected
and can be removed while in use by the caller. Move the conflicting lock from
the return to a parameter, and copy the conflicting lock.
In most cases the caller ends up putting the copy of the conflicting lock on
the stack. On i386, sizeof(struct file_lock) appears to be about 100 bytes.
We're assuming that's reasonable.
Signed-off-by: Andy Adamson <andros@citi.umich.edu>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 1cf07e4..ee140c5 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -392,15 +392,14 @@
static int do_getlk(struct file *filp, int cmd, struct file_lock *fl)
{
- struct file_lock *cfl;
+ struct file_lock cfl;
struct inode *inode = filp->f_mapping->host;
int status = 0;
lock_kernel();
/* Try local locking first */
- cfl = posix_test_lock(filp, fl);
- if (cfl != NULL) {
- locks_copy_lock(fl, cfl);
+ if (posix_test_lock(filp, fl, &cfl)) {
+ locks_copy_lock(fl, &cfl);
goto out;
}