KMSAN: uninit-value in tipc_nl_compat_bearer_enable (2)

[syzbot]

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+8b7074...@syzkaller.appspotmail.com

==================================================================
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
__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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[Xin Long]

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()