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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 <[email protected]>
Signed-off-by: J. Bruce Fields <[email protected]>
Signed-off-by: Trond Myklebust <[email protected]>
This commit is contained in:
Andy Adamson 2006-03-20 13:44:26 -05:00 • committed by Trond Myklebust
commit 8dc7c3115b
5 changed files with 28 additions and 27 deletions
Download patch file Download diff file Expand all files Collapse all files

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;
}