Re: KMSAN: uninit-value in tipc_nl_compat_bearer_enable (2)

[Xin Long]

On Thu, Mar 28, 2019 at 1:55 AM syzbot
<syzbot+8b707430713eb46e1e45@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    9536b452 kmsan: uaccess.h: fix variable name conflicts
> git tree:       kmsan
> console output: https://syzkaller.appspot.com/x/log.txt?x=15f5d583200000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=a5675814e8eae69e
> dashboard link: https://syzkaller.appspot.com/bug?extid=8b707430713eb46e1e45
> compiler:       clang version 8.0.0 (trunk 350509)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16438e1b200000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16898cd7200000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+8b707430713eb46e1e45@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> ==================================================================
> BUG: KMSAN: uninit-value in memchr+0xce/0x110 lib/string.c:961
> CPU: 0 PID: 10526 Comm: syz-executor961 Not tainted 5.0.0+ #13
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> Google 01/01/2011
> Call Trace:
>   __dump_stack lib/dump_stack.c:77 [inline]
>   dump_stack+0x173/0x1d0 lib/dump_stack.c:113
>   kmsan_report+0x12e/0x2a0 mm/kmsan/kmsan.c:600
>   __msan_warning+0x82/0xf0 mm/kmsan/kmsan_instr.c:313
>   memchr+0xce/0x110 lib/string.c:961
>   string_is_valid net/tipc/netlink_compat.c:176 [inline]
>   tipc_nl_compat_bearer_enable+0x2c4/0x910 net/tipc/netlink_compat.c:401
It's using the wrong length to check if b->name is valid when
b->name size < TIPC_MAX_BEARER_NAME. The right count
should start from tipc_bearer_config->name.

diff --git a/net/tipc/netlink_compat.c b/net/tipc/netlink_compat.c
index 4ad3586..895f368 100644
--- a/net/tipc/netlink_compat.c
+++ b/net/tipc/netlink_compat.c
@@ -397,7 +397,9 @@ static int tipc_nl_compat_bearer_enable(struct
tipc_nl_compat_cmd_doit *cmd,
        if (!bearer)
                return -EMSGSIZE;

-       len = min_t(int, TLV_GET_DATA_LEN(msg->req), TIPC_MAX_BEARER_NAME);
+       len = TLV_GET_DATA_LEN(msg->req);
+       len -= offsetof(struct tipc_bearer_config, name);
+       len = min_t(int, len, TIPC_MAX_BEARER_NAME);
        if (!string_is_valid(b->name, len))
                return -EINVAL;

The simliar thing should be done in:
tipc_nl_compat_media_set()
tipc_nl_compat_bearer_set()
tipc_nl_compat_link_set()

>   __tipc_nl_compat_doit net/tipc/netlink_compat.c:321 [inline]
>   tipc_nl_compat_doit+0x3aa/0xaf0 net/tipc/netlink_compat.c:354
>   tipc_nl_compat_handle net/tipc/netlink_compat.c:1162 [inline]
>   tipc_nl_compat_recv+0x1ae7/0x2750 net/tipc/netlink_compat.c:1265
>   genl_family_rcv_msg net/netlink/genetlink.c:601 [inline]
>   genl_rcv_msg+0x185f/0x1a60 net/netlink/genetlink.c:626
>   netlink_rcv_skb+0x431/0x620 net/netlink/af_netlink.c:2477
>   genl_rcv+0x63/0x80 net/netlink/genetlink.c:637
>   netlink_unicast_kernel net/netlink/af_netlink.c:1310 [inline]
>   netlink_unicast+0xf3e/0x1020 net/netlink/af_netlink.c:1336
>   netlink_sendmsg+0x127f/0x1300 net/netlink/af_netlink.c:1917
>   sock_sendmsg_nosec net/socket.c:622 [inline]
>   sock_sendmsg net/socket.c:632 [inline]
>   ___sys_sendmsg+0xdb9/0x11b0 net/socket.c:2115
>   __sys_sendmsg net/socket.c:2153 [inline]
>   __do_sys_sendmsg net/socket.c:2162 [inline]
>   __se_sys_sendmsg+0x305/0x460 net/socket.c:2160
>   __x64_sys_sendmsg+0x4a/0x70 net/socket.c:2160
>   do_syscall_64+0xbc/0xf0 arch/x86/entry/common.c:291
>   entry_SYSCALL_64_after_hwframe+0x63/0xe7
> RIP: 0033:0x440209
> Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7
> 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff
> ff 0f 83 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
> RSP: 002b:00007ffc77bfd0a8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
> RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440209
> RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000003
> RBP: 00000000006ca018 R08: 0000000000000000 R09: 00000000004002c8
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401a90
> R13: 0000000000401b20 R14: 0000000000000000 R15: 0000000000000000
>
> Uninit was created at:
>   kmsan_save_stack_with_flags mm/kmsan/kmsan.c:205 [inline]
>   kmsan_internal_poison_shadow+0x92/0x150 mm/kmsan/kmsan.c:159
>   kmsan_kmalloc+0xa6/0x130 mm/kmsan/kmsan_hooks.c:176
>   kmsan_slab_alloc+0xe/0x10 mm/kmsan/kmsan_hooks.c:185
>   slab_post_alloc_hook mm/slab.h:445 [inline]
>   slab_alloc_node mm/slub.c:2773 [inline]
>   __kmalloc_node_track_caller+0xe9e/0xff0 mm/slub.c:4398
>   __kmalloc_reserve net/core/skbuff.c:140 [inline]
>   __alloc_skb+0x309/0xa20 net/core/skbuff.c:208
>   alloc_skb include/linux/skbuff.h:1012 [inline]
>   netlink_alloc_large_skb net/netlink/af_netlink.c:1182 [inline]
>   netlink_sendmsg+0xb82/0x1300 net/netlink/af_netlink.c:1892
>   sock_sendmsg_nosec net/socket.c:622 [inline]
>   sock_sendmsg net/socket.c:632 [inline]
>   ___sys_sendmsg+0xdb9/0x11b0 net/socket.c:2115
>   __sys_sendmsg net/socket.c:2153 [inline]
>   __do_sys_sendmsg net/socket.c:2162 [inline]
>   __se_sys_sendmsg+0x305/0x460 net/socket.c:2160
>   __x64_sys_sendmsg+0x4a/0x70 net/socket.c:2160
>   do_syscall_64+0xbc/0xf0 arch/x86/entry/common.c:291
>   entry_SYSCALL_64_after_hwframe+0x63/0xe7
> ==================================================================
>
>
> ---
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>
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