Commit 31956502 authored May 07, 2015 by Al Viro

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 <viro@zeniv.linux.org.uk>

parent 6548fae2

fs/namei.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -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;
		}

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