security: make inode_follow_link RCU-walk aware
authorNeilBrown <neilb@suse.de>
Mon, 23 Mar 2015 02:37:39 +0000 (13:37 +1100)
committerAl Viro <viro@zeniv.linux.org.uk>
Mon, 11 May 2015 12:13:11 +0000 (08:13 -0400)
commitbda0be7ad994812960e9f8f2d2757f72cb4a96cb
treef769e7c4511b64432438f82a8426248e75a8ad7b
parent7b20ea2579238f5e0da4bc93276c1b63c960c9ef
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 <neilb@suse.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
fs/namei.c
include/linux/security.h
security/capability.c
security/security.c
security/selinux/hooks.c