linux-kernel - [PATCH 04/13] security/selinux: check for LOOKUP_RCU in _follow

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Message-ID: <20150316044319.23648.82820.stgit@notabene.brown>
Date:	Mon, 16 Mar 2015 15:43:19 +1100
From:	NeilBrown <neilb@...e.de>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 04/13] security/selinux: check for LOOKUP_RCU in
 _follow_link.

Some of dentry_has_perm() is not rcu-safe, so if LOOKUP_RCU
is set in selinux_inode_follow_link(), give up with
-ECHILD.

It is possible that dentry_has_perm could sometimes complete
in RCU more, in which case the flag could be propagated further
down the stack...

Signed-off-by: NeilBrown <neilb@...e.de>
---
 security/selinux/hooks.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index e3074e01f058..5d4de8cbfaa6 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2866,6 +2866,8 @@ static int selinux_inode_follow_link(struct dentry *dentry, int flags)
 {
 	const struct cred *cred = current_cred();

+	if (flags & LOOKUP_RCU)
+		return -ECHILD;
 	return dentry_has_perm(cred, dentry, FILE__READ);
 }

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