net: ppp: don't call sk_chk_filter twice

[ Upstream commit 3916a3192793fd3c11f69d623ef0cdbdbf9ea10a ]

Commit 568f194e8bd16c353ad50f9ab95d98b20578a39d ("net: ppp: use
sk_unattached_filter api") causes sk_chk_filter() to be called twice when
setting a PPP pass or active filter. This applies to both the generic PPP
subsystem implemented by drivers/net/ppp/ppp_generic.c and the ISDN PPP
subsystem implemented by drivers/isdn/i4l/isdn_ppp.c. The first call is from
within get_filter(). The second one is through the call chain

  ppp_ioctl() or isdn_ppp_ioctl()
  --> sk_unattached_filter_create()
      --> __sk_prepare_filter()
          --> sk_chk_filter()

The first call from within get_filter() should be deleted as get_filter() is
called just before calling sk_unattached_filter_create() later on, which
eventually calls sk_chk_filter() anyway.

For 3.15.x, this proposed change is a bugfix rather than a pure optimization as
in that branch, sk_chk_filter() may replace filter codes by other codes which
are not recognized when executing sk_chk_filter() a second time. So with
3.15.x, if sk_chk_filter() is called twice, the second invocation may yield
EINVAL (this depends on the filter codes found in the filter to be set, but
because the replacement is done for frequently used codes, this is almost
always the case). The net effect is that setting pass and/or active PPP filters
does not work anymore, since sk_unattached_filter_create() always returns
EINVAL due to the second call to sk_chk_filter(), regardless whether the filter
was originally sane or not.

Signed-off-by: Christoph Schulz <develop@kristov.de>
Acked-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/isdn/i4l/isdn_ppp.c b/drivers/isdn/i4l/isdn_ppp.c
index c81f1223b064ba33aef853c7c8436596618431f2..158ed32ac21c4b2ef355bc0c21c51eae0bcad846 100644 (file)
--- a/drivers/isdn/i4l/isdn_ppp.c
+++ b/drivers/isdn/i4l/isdn_ppp.c
@@ -442,7 +442,7 @@ static int get_filter(void __user *arg, struct sock_filter **p)
 {
        struct sock_fprog uprog;
        struct sock_filter *code = NULL;
-       int len, err;
+       int len;
 
        if (copy_from_user(&uprog, arg, sizeof(uprog)))
                return -EFAULT;
@@ -458,12 +458,6 @@ static int get_filter(void __user *arg, struct sock_filter **p)
        if (IS_ERR(code))
                return PTR_ERR(code);
 
-       err = sk_chk_filter(code, uprog.len);
-       if (err) {
-               kfree(code);
-               return err;
-       }
-
        *p = code;
        return uprog.len;
 }

diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
index 1d8664272083f6fc85533883425284324878ea9e..3c41a83a1572440328a88e31d72d15855fd5b9cd 100644 (file)
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -539,7 +539,7 @@ static int get_filter(void __user *arg, struct sock_filter **p)
 {
        struct sock_fprog uprog;
        struct sock_filter *code = NULL;
-       int len, err;
+       int len;
 
        if (copy_from_user(&uprog, arg, sizeof(uprog)))
                return -EFAULT;
@@ -554,12 +554,6 @@ static int get_filter(void __user *arg, struct sock_filter **p)
        if (IS_ERR(code))
                return PTR_ERR(code);
 
-       err = sk_chk_filter(code, uprog.len);
-       if (err) {
-               kfree(code);
-               return err;
-       }
-
        *p = code;
        return uprog.len;
 }