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Commit 5acfec25 authored by Jeff Layton's avatar Jeff Layton Committed by Steve French
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cifs: reduce false positives with inode aliasing serverino autodisable 



It turns out that not all directory inodes with dentries on the
i_dentry list are unusable here. We only consider them unusable if they
are still hashed or if they have a root dentry attached.

Full disclosure -- this check is inherently racy. There's nothing that
stops someone from slapping a new dentry onto this inode just after
this check, or hashing an existing one that's already attached. So,
this is really a "best effort" thing to work around misbehaving servers.

Signed-off-by: default avatarJeff Layton <jlayton@redhat.com>
Signed-off-by: default avatarSteve French <sfrench@us.ibm.com>
parent 67b7626a

fs/cifs/inode.c

+31 −12
Original line number Diff line number Diff line
@@ -732,15 +732,9 @@ cifs_find_inode(struct inode *inode, void *opaque) 
	if ((inode->i_mode & S_IFMT) != (fattr->cf_mode & S_IFMT))

		return 0;



	/*

	 * uh oh -- it's a directory. We can't use it since hardlinked dirs are

	 * verboten. Disable serverino and return it as if it were found, the

	 * caller can discard it, generate a uniqueid and retry the find

	 */

	if (S_ISDIR(inode->i_mode) && !list_empty(&inode->i_dentry)) {

	/* if it's not a directory or has no dentries, then flag it */

	if (S_ISDIR(inode->i_mode) && !list_empty(&inode->i_dentry))

		fattr->cf_flags |= CIFS_FATTR_INO_COLLISION;

		cifs_autodisable_serverino(CIFS_SB(inode->i_sb));

	}



	return 1;

}
@@ -754,6 +748,27 @@ cifs_init_inode(struct inode *inode, void *opaque) 
	return 0;

}



/*

 * walk dentry list for an inode and report whether it has aliases that

 * are hashed. We use this to determine if a directory inode can actually

 * be used.

 */

static bool

inode_has_hashed_dentries(struct inode *inode)

{

	struct dentry *dentry;



	spin_lock(&dcache_lock);

	list_for_each_entry(dentry, &inode->i_dentry, d_alias) {

		if (!d_unhashed(dentry) || IS_ROOT(dentry)) {

			spin_unlock(&dcache_lock);

			return true;

		}

	}

	spin_unlock(&dcache_lock);

	return false;

}



/* Given fattrs, get a corresponding inode */

struct inode *

cifs_iget(struct super_block *sb, struct cifs_fattr *fattr)
@@ -769,13 +784,17 @@ retry_iget5_locked: 


	inode = iget5_locked(sb, hash, cifs_find_inode, cifs_init_inode, fattr);

	if (inode) {

		/* was there a problematic inode number collision? */

		/* was there a potentially problematic inode collision? */

		if (fattr->cf_flags & CIFS_FATTR_INO_COLLISION) {

			fattr->cf_flags &= ~CIFS_FATTR_INO_COLLISION;



			if (inode_has_hashed_dentries(inode)) {

				cifs_autodisable_serverino(CIFS_SB(sb));

				iput(inode);

				fattr->cf_uniqueid = iunique(sb, ROOT_I);

			fattr->cf_flags &= ~CIFS_FATTR_INO_COLLISION;

				goto retry_iget5_locked;

			}

		}



		cifs_fattr_to_inode(inode, fattr);

		if (sb->s_flags & MS_NOATIME)