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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
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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 @@ out:
*/
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;