[PATCH net-next v3] genetlink: do not parse attributes for families with zero maxattr

[PATCH net-next v3] genetlink: do not parse attributes for families with zero maxattr

[Michal Kubecek]

Commit c10e6cf85e7d ("net: genetlink: push attrbuf allocation and parsing
to a separate function") moved attribute buffer allocation and attribute
parsing from genl_family_rcv_msg_doit() into a separate function
genl_family_rcv_msg_attrs_parse() which, unlike the previous code, calls
__nlmsg_parse() even if family->maxattr is 0 (i.e. the family does its own
parsing). The parser error is ignored and does not propagate out of
genl_family_rcv_msg_attrs_parse() but an error message ("Unknown attribute
type") is set in extack and if further processing generates no error or
warning, it stays there and is interpreted as a warning by userspace.

Dumpit requests are not affected as genl_family_rcv_msg_dumpit() bypasses
the call of genl_family_rcv_msg_attrs_parse() if family->maxattr is zero.
Move this logic inside genl_family_rcv_msg_attrs_parse() so that we don't
have to handle it in each caller.

v3: put the check inside genl_family_rcv_msg_attrs_parse()
v2: adjust also argument of genl_family_rcv_msg_attrs_free()

Fixes: c10e6cf85e7d ("net: genetlink: push attrbuf allocation and parsing to a separate function")
Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
---
 net/netlink/genetlink.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index ecc2bd3e73e4..0522b2b1fd95 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -483,6 +483,9 @@ genl_family_rcv_msg_attrs_parse(const struct genl_family *family,
 	struct nlattr **attrbuf;
 	int err;
 
+	if (!family->maxattr)
+		return NULL;
+
 	if (parallel) {
 		attrbuf = kmalloc_array(family->maxattr + 1,
 					sizeof(struct nlattr *), GFP_KERNEL);
@@ -582,9 +585,6 @@ static int genl_family_rcv_msg_dumpit(const struct genl_family *family,
 	if (nlh->nlmsg_len < nlmsg_msg_size(hdrlen))
 		return -EINVAL;
 
-	if (!family->maxattr)
-		goto no_attrs;
-
 	attrs = genl_family_rcv_msg_attrs_parse(family, nlh, extack,
 						ops, hdrlen,
 						GENL_DONT_VALIDATE_DUMP_STRICT,
@@ -649,7 +649,6 @@ static int genl_family_rcv_msg_doit(const struct genl_family *family,
 	attrbuf = genl_family_rcv_msg_attrs_parse(family, nlh, extack,
 						  ops, hdrlen,
 						  GENL_DONT_VALIDATE_STRICT,
-						  family->maxattr &&
 						  family->parallel_ops);
 	if (IS_ERR(attrbuf))
 		return PTR_ERR(attrbuf);
@@ -676,8 +675,7 @@ static int genl_family_rcv_msg_doit(const struct genl_family *family,
 		family->post_doit(ops, skb, &info);
 
 out:
-	genl_family_rcv_msg_attrs_free(family, attrbuf,
-				       family->maxattr && family->parallel_ops);
+	genl_family_rcv_msg_attrs_free(family, attrbuf, family->parallel_ops);
 
 	return err;
 }
-- 
2.23.0

Re: [PATCH net-next v3] genetlink: do not parse attributes for families with zero maxattr

[Jiri Pirko]

Fri, Oct 11, 2019 at 09:40:09AM CEST, mkubecek@suse.cz wrote:
>Commit c10e6cf85e7d ("net: genetlink: push attrbuf allocation and parsing
>to a separate function") moved attribute buffer allocation and attribute
>parsing from genl_family_rcv_msg_doit() into a separate function
>genl_family_rcv_msg_attrs_parse() which, unlike the previous code, calls
>__nlmsg_parse() even if family->maxattr is 0 (i.e. the family does its own
>parsing). The parser error is ignored and does not propagate out of
>genl_family_rcv_msg_attrs_parse() but an error message ("Unknown attribute
>type") is set in extack and if further processing generates no error or
>warning, it stays there and is interpreted as a warning by userspace.
>
>Dumpit requests are not affected as genl_family_rcv_msg_dumpit() bypasses
>the call of genl_family_rcv_msg_attrs_parse() if family->maxattr is zero.
>Move this logic inside genl_family_rcv_msg_attrs_parse() so that we don't
>have to handle it in each caller.
>
>v3: put the check inside genl_family_rcv_msg_attrs_parse()
>v2: adjust also argument of genl_family_rcv_msg_attrs_free()
>
>Fixes: c10e6cf85e7d ("net: genetlink: push attrbuf allocation and parsing to a separate function")
>Signed-off-by: Michal Kubecek <mkubecek@suse.cz>

Acked-by: Jiri Pirko <jiri@mellanox.com>

Thanks!

Re: [PATCH net-next v3] genetlink: do not parse attributes for families with zero maxattr

[Jakub Kicinski]

On Fri, 11 Oct 2019 09:40:09 +0200, Michal Kubecek wrote:
> Commit c10e6cf85e7d ("net: genetlink: push attrbuf allocation and parsing
> to a separate function") moved attribute buffer allocation and attribute
> parsing from genl_family_rcv_msg_doit() into a separate function
> genl_family_rcv_msg_attrs_parse() which, unlike the previous code, calls
> __nlmsg_parse() even if family->maxattr is 0 (i.e. the family does its own
> parsing). The parser error is ignored and does not propagate out of
> genl_family_rcv_msg_attrs_parse() but an error message ("Unknown attribute
> type") is set in extack and if further processing generates no error or
> warning, it stays there and is interpreted as a warning by userspace.
> 
> Dumpit requests are not affected as genl_family_rcv_msg_dumpit() bypasses
> the call of genl_family_rcv_msg_attrs_parse() if family->maxattr is zero.
> Move this logic inside genl_family_rcv_msg_attrs_parse() so that we don't
> have to handle it in each caller.
> 
> v3: put the check inside genl_family_rcv_msg_attrs_parse()
> v2: adjust also argument of genl_family_rcv_msg_attrs_free()
> 
> Fixes: c10e6cf85e7d ("net: genetlink: push attrbuf allocation and parsing to a separate function")
> Signed-off-by: Michal Kubecek <mkubecek@suse.cz>

Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>

Re: [PATCH net-next v3] genetlink: do not parse attributes for families with zero maxattr

[David Miller]

From: Michal Kubecek <mkubecek@suse.cz>
Date: Fri, 11 Oct 2019 09:40:09 +0200

> Commit c10e6cf85e7d ("net: genetlink: push attrbuf allocation and parsing
> to a separate function") moved attribute buffer allocation and attribute
> parsing from genl_family_rcv_msg_doit() into a separate function
> genl_family_rcv_msg_attrs_parse() which, unlike the previous code, calls
> __nlmsg_parse() even if family->maxattr is 0 (i.e. the family does its own
> parsing). The parser error is ignored and does not propagate out of
> genl_family_rcv_msg_attrs_parse() but an error message ("Unknown attribute
> type") is set in extack and if further processing generates no error or
> warning, it stays there and is interpreted as a warning by userspace.
> 
> Dumpit requests are not affected as genl_family_rcv_msg_dumpit() bypasses
> the call of genl_family_rcv_msg_attrs_parse() if family->maxattr is zero.
> Move this logic inside genl_family_rcv_msg_attrs_parse() so that we don't
> have to handle it in each caller.
> 
> v3: put the check inside genl_family_rcv_msg_attrs_parse()
> v2: adjust also argument of genl_family_rcv_msg_attrs_free()
> 
> Fixes: c10e6cf85e7d ("net: genetlink: push attrbuf allocation and parsing to a separate function")
> Signed-off-by: Michal Kubecek <mkubecek@suse.cz>

Applied, thanks.