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/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
index 1143cfb..f6ab762 100644
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -2639,7 +2639,7 @@
struct nfs4_stateid *lock_stp;
struct file *filp;
struct file_lock file_lock;
- struct file_lock *conflock;
+ struct file_lock conflock;
int status = 0;
unsigned int strhashval;
@@ -2775,11 +2775,11 @@
/* XXX There is a race here. Future patch needed to provide
* an atomic posix_lock_and_test_file
*/
- if (!(conflock = posix_test_lock(filp, &file_lock))) {
+ if (!posix_test_lock(filp, &file_lock, &conflock)) {
status = nfserr_serverfault;
goto out;
}
- nfs4_set_lock_denied(conflock, &lock->lk_denied);
+ nfs4_set_lock_denied(&conflock, &lock->lk_denied);
out:
if (status && lock->lk_is_new && lock_sop)
release_stateowner(lock_sop);
@@ -2800,7 +2800,7 @@
struct inode *inode;
struct file file;
struct file_lock file_lock;
- struct file_lock *conflicting_lock;
+ struct file_lock conflock;
int status;
if (nfs4_in_grace())
@@ -2864,10 +2864,9 @@
file.f_dentry = current_fh->fh_dentry;
status = nfs_ok;
- conflicting_lock = posix_test_lock(&file, &file_lock);
- if (conflicting_lock) {
+ if (posix_test_lock(&file, &file_lock, &conflock)) {
status = nfserr_denied;
- nfs4_set_lock_denied(conflicting_lock, &lockt->lt_denied);
+ nfs4_set_lock_denied(&conflock, &lockt->lt_denied);
}
out:
nfs4_unlock_state();
