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ceph: fix unsafe dcache access in ceph_encode_dentry_release 

Accessing d_parent requires some sort of locking or it could vanish
out from under us. Since we take the d_lock anyway, use that to fetch
d_parent and take a reference to it, and then use that reference to
call ceph_encode_inode_release.

Link: http://tracker.ceph.com/issues/18148
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Reviewed-by: Yan, Zheng <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
This commit is contained in:
Jeff Layton 2016-12-15 08:37:58 -05:00 committed by Ilya Dryomov
parent fd36a71762
commit adf0d68701
1 changed files with 5 additions and 2 deletions
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7
fs/ceph/caps.c
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@ -3926,7 +3926,7 @@ int ceph_encode_inode_release(void **p, struct inode *inode,
int ceph_encode_dentry_release(void **p, struct dentry *dentry,
int mds, int drop, int unless)
{
struct inode *dir = d_inode(dentry->d_parent);
struct dentry *parent;
struct ceph_mds_request_release *rel = *p;
struct ceph_dentry_info *di = ceph_dentry(dentry);
int force = 0;
@ -3941,9 +3941,12 @@ int ceph_encode_dentry_release(void **p, struct dentry *dentry,
spin_lock(&dentry->d_lock);
if (di->lease_session && di->lease_session->s_mds == mds)
force = 1;
parent = dget(dentry->d_parent);
spin_unlock(&dentry->d_lock);
ret = ceph_encode_inode_release(p, dir, mds, drop, unless, force);
ret = ceph_encode_inode_release(p, d_inode(parent), mds, drop,
unless, force);
dput(parent);
spin_lock(&dentry->d_lock);
if (ret && di->lease_session && di->lease_session->s_mds == mds) {