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be careful with nd->inode in path_init() and follow_dotdot_rcu() 

in the former we simply check if dentry is still valid after picking
its ->d_inode; in the latter we fetch ->d_inode in the same places
where we fetch dentry and its ->d_seq, under the same checks.

Cc: stable@vger.kernel.org # 2.6.38+
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2014-09-13 21:59:43 -04:00
parent 7bd88377d4
commit 4023bfc9f3
1 changed files with 13 additions and 2 deletions
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15
fs/namei.c
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@ -1142,6 +1142,7 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
static int follow_dotdot_rcu(struct nameidata *nd)
{
struct inode *inode = nd->inode;
if (!nd->root.mnt)
set_root_rcu(nd);
@ -1155,6 +1156,7 @@ static int follow_dotdot_rcu(struct nameidata *nd)
struct dentry *parent = old->d_parent;
unsigned seq;
inode = parent->d_inode;
seq = read_seqcount_begin(&parent->d_seq);
if (read_seqcount_retry(&old->d_seq, nd->seq))
goto failed;
@ -1164,6 +1166,7 @@ static int follow_dotdot_rcu(struct nameidata *nd)
}
if (!follow_up_rcu(&nd->path))
break;
inode = nd->path.dentry->d_inode;
nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
}
while (d_mountpoint(nd->path.dentry)) {
@ -1173,11 +1176,12 @@ static int follow_dotdot_rcu(struct nameidata *nd)
break;
nd->path.mnt = &mounted->mnt;
nd->path.dentry = mounted->mnt.mnt_root;
inode = nd->path.dentry->d_inode;
nd->seq = read_seqcount_begin(&nd->path.dentry->d_seq);
if (read_seqretry(&mount_lock, nd->m_seq))
goto failed;
}
nd->inode = nd->path.dentry->d_inode;
nd->inode = inode;
return 0;
failed:
@ -1904,7 +1908,14 @@ static int path_init(int dfd, const char *name, unsigned int flags,
}
nd->inode = nd->path.dentry->d_inode;
return 0;
if (!(flags & LOOKUP_RCU))
return 0;
if (likely(!read_seqcount_retry(&nd->path.dentry->d_seq, nd->seq)))
return 0;
if (!(nd->flags & LOOKUP_ROOT))
nd->root.mnt = NULL;
rcu_read_unlock();
return -ECHILD;
}
static inline int lookup_last(struct nameidata *nd, struct path *path)