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netlink: Fix spectre v1 gadget in netlink_create()

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[ Upstream commit bc5b6c0b62 ]

'protocol' is a user-controlled value, so sanitize it after the bounds
check to avoid using it for speculative out-of-bounds access to arrays
indexed by it.

This addresses the following accesses detected with the help of smatch:

* net/netlink/af_netlink.c:654 __netlink_create() warn: potential
  spectre issue 'nlk_cb_mutex_keys' [w]

* net/netlink/af_netlink.c:654 __netlink_create() warn: potential
  spectre issue 'nlk_cb_mutex_key_strings' [w]

* net/netlink/af_netlink.c:685 netlink_create() warn: potential spectre
  issue 'nl_table' [w] (local cap)

Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Jeremy Cline <jcline@redhat.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jeremy Cline
2018-07-31 21:13:16 +00:00
committed by Greg Kroah-Hartman
parent ab9a0f80bc
commit 67f0a2887b
1 changed files with 2 additions and 0 deletions
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2
net/netlink/af_netlink.c
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@ -62,6 +62,7 @@
#include <asm/cacheflush.h> #include <asm/cacheflush.h>
#include <linux/hash.h> #include <linux/hash.h>
#include <linux/genetlink.h> #include <linux/genetlink.h>
#include <linux/nospec.h>
#include <net/net_namespace.h> #include <net/net_namespace.h>
#include <net/sock.h> #include <net/sock.h>
@ -654,6 +655,7 @@ static int netlink_create(struct net *net, struct socket *sock, int protocol,
if (protocol < 0 || protocol >= MAX_LINKS) if (protocol < 0 || protocol >= MAX_LINKS)
return -EPROTONOSUPPORT; return -EPROTONOSUPPORT;
protocol = array_index_nospec(protocol, MAX_LINKS);
netlink_lock_table(); netlink_lock_table();
#ifdef CONFIG_MODULES #ifdef CONFIG_MODULES