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locks,lockd: fix race in nlmsvc_testlock

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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>
This commit is contained in:
Andy Adamson 2006-03-20 13:44:26 -05:00 committed by Trond Myklebust
parent 2e0af86f61
commit 8dc7c3115b
5 changed files with 28 additions and 27 deletions
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12
fs/lockd/svclock.c
View file

@ -376,8 +376,6 @@ u32
nlmsvc_testlock(struct nlm_file *file, struct nlm_lock *lock,
struct nlm_lock *conflock)
{
struct file_lock *fl;
dprintk("lockd: nlmsvc_testlock(%s/%ld, ty=%d, %Ld-%Ld)\n",
file->f_file->f_dentry->d_inode->i_sb->s_id,
file->f_file->f_dentry->d_inode->i_ino,
@ -385,14 +383,14 @@ nlmsvc_testlock(struct nlm_file *file, struct nlm_lock *lock,
(long long)lock->fl.fl_start,
(long long)lock->fl.fl_end);
if ((fl = posix_test_lock(file->f_file, &lock->fl)) != NULL) {
if (posix_test_lock(file->f_file, &lock->fl, &conflock->fl)) {
dprintk("lockd: conflicting lock(ty=%d, %Ld-%Ld)\n",
fl->fl_type, (long long)fl->fl_start,
(long long)fl->fl_end);
conflock->fl.fl_type,
(long long)conflock->fl.fl_start,
(long long)conflock->fl.fl_end);
conflock->caller = "somehost"; /* FIXME */
conflock->oh.len = 0; /* don't return OH info */
conflock->svid = fl->fl_pid;
conflock->fl = *fl;
conflock->svid = conflock->fl.fl_pid;
return nlm_lck_denied;
}

21
fs/locks.c
View file

@ -672,8 +672,9 @@ static int locks_block_on_timeout(struct file_lock *blocker, struct file_lock *w
return result;
}
struct file_lock *
posix_test_lock(struct file *filp, struct file_lock *fl)
int
posix_test_lock(struct file *filp, struct file_lock *fl,
struct file_lock *conflock)
{
struct file_lock *cfl;
@ -684,9 +685,13 @@ posix_test_lock(struct file *filp, struct file_lock *fl)
if (posix_locks_conflict(cfl, fl))
break;
}
if (cfl) {
locks_copy_lock(conflock, cfl);
unlock_kernel();
return 1;
}
unlock_kernel();
return (cfl);
return 0;
}
EXPORT_SYMBOL(posix_test_lock);
@ -1563,7 +1568,7 @@ asmlinkage long sys_flock(unsigned int fd, unsigned int cmd)
*/
int fcntl_getlk(struct file *filp, struct flock __user *l)
{
struct file_lock *fl, file_lock;
struct file_lock *fl, cfl, file_lock;
struct flock flock;
int error;
@ -1587,7 +1592,7 @@ int fcntl_getlk(struct file *filp, struct flock __user *l)
else
fl = (file_lock.fl_type == F_UNLCK ? NULL : &file_lock);
} else {
fl = posix_test_lock(filp, &file_lock);
fl = (posix_test_lock(filp, &file_lock, &cfl) ? &cfl : NULL);
}
flock.l_type = F_UNLCK;
@ -1717,7 +1722,7 @@ int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
*/
int fcntl_getlk64(struct file *filp, struct flock64 __user *l)
{
struct file_lock *fl, file_lock;
struct file_lock *fl, cfl, file_lock;
struct flock64 flock;
int error;
@ -1741,7 +1746,7 @@ int fcntl_getlk64(struct file *filp, struct flock64 __user *l)
else
fl = (file_lock.fl_type == F_UNLCK ? NULL : &file_lock);
} else {
fl = posix_test_lock(filp, &file_lock);
fl = (posix_test_lock(filp, &file_lock, &cfl) ? &cfl : NULL);
}
flock.l_type = F_UNLCK;

7
fs/nfs/file.c
View file

@ -392,15 +392,14 @@ nfs_file_write(struct kiocb *iocb, const char __user *buf, size_t count, loff_t
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;
}

13
fs/nfsd/nfs4state.c
View file

@ -2639,7 +2639,7 @@ nfsd4_lock(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nfsd4_lock
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 @@ nfsd4_lock(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nfsd4_lock
/* 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 @@ nfsd4_lockt(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nfsd4_lock
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 @@ nfsd4_lockt(struct svc_rqst *rqstp, struct svc_fh *current_fh, struct nfsd4_lock
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();

2
include/linux/fs.h
View file

@ -754,7 +754,7 @@ extern void locks_init_lock(struct file_lock *);
extern void locks_copy_lock(struct file_lock *, struct file_lock *);
extern void locks_remove_posix(struct file *, fl_owner_t);
extern void locks_remove_flock(struct file *);
extern struct file_lock *posix_test_lock(struct file *, struct file_lock *);
extern int posix_test_lock(struct file *, struct file_lock *, struct file_lock *);
extern int posix_lock_file(struct file *, struct file_lock *);
extern int posix_lock_file_wait(struct file *, struct file_lock *);
extern int posix_unblock_lock(struct file *, struct file_lock *);