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

[Paolo Abeni]

On Sun, 2023-09-24 at 15:03 +0900, 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: syzbot+5138ca807af9d2b42574@xxxxxxxxxxxxxxxxxxxxxxxxx
> Closes: https://syzkaller.appspot.com/bug?extid=5138ca807af9d2b42574
> Signed-off-by: Shigeru Yoshida <syoshida@xxxxxxxxxx>
> ---
>  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;

I have the same comment as for the other tipc patch, please use
nla_strscpy instead, thanks!

Paolo