From 31956502dd2c9432523d01373a9dc0e5931cfa1c Mon Sep 17 00:00:00 2001 From: Al Viro Date: Thu, 7 May 2015 20:37:40 -0400 Subject: [PATCH] namei: make may_follow_link() safe in RCU mode We *can't* call that audit garbage in RCU mode - it's doing a weird mix of allocations (GFP_NOFS, immediately followed by GFP_KERNEL) and I'm not touching that... thing again. So if this security sclero^Whardening feature gets triggered when we are in RCU mode, tough - we'll fail with -ECHILD and have everything restarted in non-RCU mode. Only to hit the same test and fail, this time with EACCES and with (oh, rapture) an audit spew produced. Signed-off-by: Al Viro --- fs/namei.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/namei.c b/fs/namei.c index 998c3c2c9488..20bf494307c9 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -794,6 +794,9 @@ static inline int may_follow_link(struct nameidata *nd) if (uid_eq(parent->i_uid, inode->i_uid)) return 0; + if (nd->flags & LOOKUP_RCU) + return -ECHILD; + audit_log_link_denied("follow_link", &nd->stack[0].link); return -EACCES; }