Commit 72392ed0 authored Dec 05, 2014 by Rasmus Villemoes Committed by Greg Kroah-Hartman Jan 09, 2015

kernfs: Fix kernfs_name_compare



Returning a difference from a comparison functions is usually wrong
(see acbbe6fb "kcmp: fix standard comparison bug" for the long
story). Here there is the additional twist that if the void pointers
ns and kn->ns happen to differ by a multiple of 2^32,
kernfs_name_compare returns 0, falsely reporting a match to the
caller.

Technically 'hash - kn->hash' is ok since the hashes are restricted to
31 bits, but it's better to avoid that subtlety.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent b7392d22

fs/kernfs/dir.c

+8 −4

Original line number	Diff line number	Diff line
		@@ -201,10 +201,14 @@ static unsigned int kernfs_name_hash(const char name, const void ns)
		static int kernfs_name_compare(unsigned int hash, const char *name,
		const void ns, const struct kernfs_node kn)
		{
		if (hash != kn->hash)
		return hash - kn->hash;
		if (ns != kn->ns)
		return ns - kn->ns;
		if (hash < kn->hash)
		return -1;
		if (hash > kn->hash)
		return 1;
		if (ns < kn->ns)
		return -1;
		if (ns > kn->ns)
		return 1;
		return strcmp(name, kn->name);
		}