From bda0be7ad994812960e9f8f2d2757f72cb4a96cb Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Mon, 23 Mar 2015 13:37:39 +1100 Subject: security: make inode_follow_link RCU-walk aware inode_follow_link now takes an inode and rcu flag as well as the dentry. inode is used in preference to d_backing_inode(dentry), particularly in RCU-walk mode. selinux_inode_follow_link() gets dentry_has_perm() and inode_has_perm() open-coded into it so that it can call avc_has_perm_flags() in way that is safe if LOOKUP_RCU is set. Calling avc_has_perm_flags() with rcu_read_lock() held means that when avc_has_perm_noaudit calls avc_compute_av(), the attempt to rcu_read_unlock() before calling security_compute_av() will not actually drop the RCU read-lock. However as security_compute_av() is completely in a read_lock()ed region, it should be safe with the RCU read-lock held. Signed-off-by: NeilBrown Signed-off-by: Al Viro --- fs/namei.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'fs/namei.c') diff --git a/fs/namei.c b/fs/namei.c index 33b655de0ec0..0fa7af23cff6 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -881,8 +881,9 @@ const char *get_link(struct nameidata *nd) touch_atime(&last->link); - error = security_inode_follow_link(dentry); - if (error) + error = security_inode_follow_link(dentry, inode, + nd->flags & LOOKUP_RCU); + if (unlikely(error)) return ERR_PTR(error); nd->last_type = LAST_BIND; -- cgit v1.2.3-55-g7522