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locks: fix locks_mandatory_locked to respect file-private locks

Browse source 
As Trond pointed out, you can currently deadlock yourself by setting a
file-private lock on a file that requires mandatory locking and then
trying to do I/O on it.

Avoid this problem by plumbing some knowledge of file-private locks into
the mandatory locking code. In order to do this, we must pass down
information about the struct file that's being used to
locks_verify_locked.

Reported-by: Trond Myklebust <[email protected]>
Signed-off-by: Jeff Layton <[email protected]>
Acked-by: J. Bruce Fields <[email protected]>
This commit is contained in:
Jeff Layton 2014-03-10 09:54:15 -04:00
commit d7a06983a0
5 changed files with 18 additions and 17 deletions
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7
fs/locks.c
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@ -1155,13 +1155,14 @@ EXPORT_SYMBOL(posix_lock_file_wait);
/**
* locks_mandatory_locked - Check for an active lock
* @inode: the file to check
* @file: the file to check
*
* Searches the inode's list of locks to find any POSIX locks which conflict.
* This function is called from locks_verify_locked() only.
*/
int locks_mandatory_locked(struct inode *inode)
int locks_mandatory_locked(struct file *file)
{
struct inode *inode = file_inode(file);
fl_owner_t owner = current->files;
struct file_lock *fl;
@ -1172,7 +1173,7 @@ int locks_mandatory_locked(struct inode *inode)
for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
if (!IS_POSIX(fl))
continue;
if (fl->fl_owner != owner)
if (fl->fl_owner != owner && fl->fl_owner != (fl_owner_t)file)
break;
}
spin_unlock(&inode->i_lock);