Re: [tipc-discussion] [PATCH] tipc: Fix uninit-value access in tipc_nl_node_reset_link_stats()

[Jon M. <jm...@re...>]

On 2023-09-24 02:03, Shigeru Yoshida wrote:
> syzbot reported the following uninit-value access issue:
>
> =====================================================
> BUG: KMSAN: uninit-value in strlen lib/string.c:418 [inline]
> BUG: KMSAN: uninit-value in strstr+0xb8/0x2f0 lib/string.c:756
>   strlen lib/string.c:418 [inline]
>   strstr+0xb8/0x2f0 lib/string.c:756
>   tipc_nl_node_reset_link_stats+0x3ea/0xb50 net/tipc/node.c:2595
>   genl_family_rcv_msg_doit net/netlink/genetlink.c:971 [inline]
>   genl_family_rcv_msg net/netlink/genetlink.c:1051 [inline]
>   genl_rcv_msg+0x11ec/0x1290 net/netlink/genetlink.c:1066
>   netlink_rcv_skb+0x371/0x650 net/netlink/af_netlink.c:2545
>   genl_rcv+0x40/0x60 net/netlink/genetlink.c:1075
>   netlink_unicast_kernel net/netlink/af_netlink.c:1342 [inline]
>   netlink_unicast+0xf47/0x1250 net/netlink/af_netlink.c:1368
>   netlink_sendmsg+0x1238/0x13d0 net/netlink/af_netlink.c:1910
>   sock_sendmsg_nosec net/socket.c:730 [inline]
>   sock_sendmsg net/socket.c:753 [inline]
>   ____sys_sendmsg+0x9c2/0xd60 net/socket.c:2541
>   ___sys_sendmsg+0x28d/0x3c0 net/socket.c:2595
>   __sys_sendmsg net/socket.c:2624 [inline]
>   __do_sys_sendmsg net/socket.c:2633 [inline]
>   __se_sys_sendmsg net/socket.c:2631 [inline]
>   __x64_sys_sendmsg+0x307/0x490 net/socket.c:2631
>   do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>   do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
>   entry_SYSCALL_64_after_hwframe+0x63/0xcd
>
> Uninit was created at:
>   slab_post_alloc_hook+0x12f/0xb70 mm/slab.h:767
>   slab_alloc_node mm/slub.c:3478 [inline]
>   kmem_cache_alloc_node+0x577/0xa80 mm/slub.c:3523
>   kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:559
>   __alloc_skb+0x318/0x740 net/core/skbuff.c:650
>   alloc_skb include/linux/skbuff.h:1286 [inline]
>   netlink_alloc_large_skb net/netlink/af_netlink.c:1214 [inline]
>   netlink_sendmsg+0xb34/0x13d0 net/netlink/af_netlink.c:1885
>   sock_sendmsg_nosec net/socket.c:730 [inline]
>   sock_sendmsg net/socket.c:753 [inline]
>   ____sys_sendmsg+0x9c2/0xd60 net/socket.c:2541
>   ___sys_sendmsg+0x28d/0x3c0 net/socket.c:2595
>   __sys_sendmsg net/socket.c:2624 [inline]
>   __do_sys_sendmsg net/socket.c:2633 [inline]
>   __se_sys_sendmsg net/socket.c:2631 [inline]
>   __x64_sys_sendmsg+0x307/0x490 net/socket.c:2631
>   do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>   do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
>   entry_SYSCALL_64_after_hwframe+0x63/0xcd
>
> Link names must be null-terminated strings. If a link name which is not
> null-terminated is passed through netlink, strstr() and similar functions
> can cause buffer overrun. This causes the above issue.
>
> This patch fixes this issue by returning -EINVAL if a non-null-terminated
> link name is passed.
>
> Fixes: ae36342b50a9 ("tipc: add link stat reset to new netlink api")
> Reported-and-tested-by: syz...@sy...
> Closes: https://syzkaller.appspot.com/bug?extid=5138ca807af9d2b42574
> Signed-off-by: Shigeru Yoshida <syo...@re...>
> ---
>   net/tipc/node.c | 4 ++++
>   1 file changed, 4 insertions(+)
>
> diff --git a/net/tipc/node.c b/net/tipc/node.c
> index 3105abe97bb9..f167bdafc034 100644
> --- a/net/tipc/node.c
> +++ b/net/tipc/node.c
> @@ -2586,6 +2586,10 @@ int tipc_nl_node_reset_link_stats(struct sk_buff *skb, struct genl_info *info)
>   
>   	link_name = nla_data(attrs[TIPC_NLA_LINK_NAME]);
>   
> +	if (link_name[strnlen(link_name,
> +			      nla_len(attrs[TIPC_NLA_LINK_NAME]))] != '\0')
> +		return -EINVAL;
> +
>   	err = -EINVAL;
>   	if (!strcmp(link_name, tipc_bclink_name)) {
>   		err = tipc_bclink_reset_stats(net, tipc_bc_sndlink(net));
Acked-by: Jon Maloy <jm...@re...>