[net] tipc: check attribute length for bearer name

[net] tipc: check attribute length for bearer name

[Hoang Le]

syzbot reported uninit-value:
=====================================================
BUG: KMSAN: uninit-value in string_nocheck lib/vsprintf.c:644 [inline]
BUG: KMSAN: uninit-value in string+0x4f9/0x6f0 lib/vsprintf.c:725
 string_nocheck lib/vsprintf.c:644 [inline]
 string+0x4f9/0x6f0 lib/vsprintf.c:725
 vsnprintf+0x2222/0x3650 lib/vsprintf.c:2806
 vprintk_store+0x537/0x2150 kernel/printk/printk.c:2158
 vprintk_emit+0x28b/0xab0 kernel/printk/printk.c:2256
 vprintk_default+0x86/0xa0 kernel/printk/printk.c:2283
 vprintk+0x15f/0x180 kernel/printk/printk_safe.c:50
 _printk+0x18d/0x1cf kernel/printk/printk.c:2293
 tipc_enable_bearer net/tipc/bearer.c:371 [inline]
 __tipc_nl_bearer_enable+0x2022/0x22a0 net/tipc/bearer.c:1033
 tipc_nl_bearer_enable+0x6c/0xb0 net/tipc/bearer.c:1042
 genl_family_rcv_msg_doit net/netlink/genetlink.c:731 [inline]

- Do sanity check the attribute length for TIPC_NLA_BEARER_NAME.
- Do not use 'illegal name' in printing message.

Reported-by: syzbot+e820fdc8ce362f2dea51@syzkaller.appspotmail.com
Acked-by: Jon Maloy <jmaloy@redhat.com>
Signed-off-by: Hoang Le <hoang.h.le@dektech.com.au>
---
 net/tipc/bearer.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/tipc/bearer.c b/net/tipc/bearer.c
index 6d39ca05f249..0fd7554c7cde 100644
--- a/net/tipc/bearer.c
+++ b/net/tipc/bearer.c
@@ -258,10 +258,10 @@ static int tipc_enable_bearer(struct net *net, const char *name,
 	char *errstr = "";
 	u32 i;
 
-	if (!bearer_name_validate(name, &b_names)) {
-		errstr = "illegal name";
+	if (strlen(name) > TIPC_MAX_BEARER_NAME ||
+	    !bearer_name_validate(name, &b_names)) {
 		NL_SET_ERR_MSG(extack, "Illegal name");
-		goto rejected;
+		return res;
 	}
 
 	if (prio > TIPC_MAX_LINK_PRI && prio != TIPC_MEDIA_LINK_PRI) {
-- 
2.30.2

Re: [net] tipc: check attribute length for bearer name

[Jakub Kicinski]

On Wed,  1 Jun 2022 08:48:53 +0700 Hoang Le wrote:
> diff --git a/net/tipc/bearer.c b/net/tipc/bearer.c
> index 6d39ca05f249..0fd7554c7cde 100644
> --- a/net/tipc/bearer.c
> +++ b/net/tipc/bearer.c
> @@ -258,10 +258,10 @@ static int tipc_enable_bearer(struct net *net, const char *name,
>  	char *errstr = "";
>  	u32 i;
>  
> -	if (!bearer_name_validate(name, &b_names)) {
> -		errstr = "illegal name";
> +	if (strlen(name) > TIPC_MAX_BEARER_NAME ||
> +	    !bearer_name_validate(name, &b_names)) {

The strlen() check looks unnecessary, the first thing
bearer_name_validate() does is:

	/* copy bearer name & ensure length is OK */
	if (strscpy(name_copy, name, TIPC_MAX_BEARER_NAME) < 0)
		return 0;

So it will handle non-terminated or over-sized names correctly already.

>  		NL_SET_ERR_MSG(extack, "Illegal name");
> -		goto rejected;
> +		return res;

Seems like we only need the change of goto to return for the fix.