Subject: KMSAN: uninit-value in __nla_validate_parse (2)

From: syzbot <[email-masked]>
Date: Mon, 11 Jan 2021 07:30:15 -0800

Hello,

syzbot found the following issue on:

HEAD commit:    73d62e81 kmsan: random: prevent boot-time reports in _mix_..
git tree:       https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=153a38f7500000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2cdf4151c9653e32
dashboard link: https://syzkaller.appspot.com/bug?extid=2624e3778b18fc497c92
compiler:       clang version 11.0.0 (https://github.com/llvm/llvm-project.git ca2dcbd030eadbf0aa9b660efe864ff08af6e18b)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17ef8c3f500000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12bee8f7500000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

netlink: 4 bytes leftover after parsing attributes in process `syz-executor224'.
=====================================================
BUG: KMSAN: uninit-value in nla_ok include/net/netlink.h:1159 [inline]
BUG: KMSAN: uninit-value in __nla_validate_parse+0x5fd/0x4e00 lib/nlattr.c:576
CPU: 0 PID: 8270 Comm: syz-executor224 Not tainted 5.10.0-rc4-syzkaller #0
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+0x21c/0x280 lib/dump_stack.c:118
 kmsan_report+0xf7/0x1e0 mm/kmsan/kmsan_report.c:118
 __msan_warning+0x5f/0xa0 mm/kmsan/kmsan_instr.c:197
 nla_ok include/net/netlink.h:1159 [inline]
 __nla_validate_parse+0x5fd/0x4e00 lib/nlattr.c:576
 __nla_parse+0x141/0x150 lib/nlattr.c:685
 nla_parse_nested include/net/netlink.h:1212 [inline]
 fl_set_erspan_opt+0x39a/0xe60 net/sched/cls_flower.c:1206
 fl_set_enc_opt net/sched/cls_flower.c:1365 [inline]
 fl_set_key+0x810d/0xbb60 net/sched/cls_flower.c:1642
 fl_set_parms net/sched/cls_flower.c:1880 [inline]
 fl_change+0x1226/0x7ae0 net/sched/cls_flower.c:1979
 tc_new_tfilter+0x37c1/0x58e0 net/sched/cls_api.c:2129
 rtnetlink_rcv_msg+0xe94/0x18b0 net/core/rtnetlink.c:5553
 netlink_rcv_skb+0x70a/0x820 net/netlink/af_netlink.c:2494
 rtnetlink_rcv+0x50/0x60 net/core/rtnetlink.c:5580
 netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
 netlink_unicast+0x11da/0x14b0 net/netlink/af_netlink.c:1330
 netlink_sendmsg+0x173c/0x1840 net/netlink/af_netlink.c:1919
 sock_sendmsg_nosec net/socket.c:651 [inline]
 sock_sendmsg net/socket.c:671 [inline]
 ____sys_sendmsg+0xc7a/0x1240 net/socket.c:2353
 ___sys_sendmsg net/socket.c:2407 [inline]
 __sys_sendmmsg+0xa56/0x1060 net/socket.c:2497
 __do_sys_sendmmsg net/socket.c:2526 [inline]
 __se_sys_sendmmsg+0xbd/0xe0 net/socket.c:2523
 __x64_sys_sendmmsg+0x56/0x70 net/socket.c:2523
 do_syscall_64+0x9f/0x140 arch/x86/entry/common.c:48
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x441739
Code: e8 5c ad 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 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 bb 09 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffca52cefc8 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000441739
RDX: 010efe10675dec16 RSI: 0000000020000200 RDI: 0000000000000003
RBP: 00007ffca52cefd0 R08: 0000000120080522 R09: 0000000120080522
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004a2a70
R13: 0000000000402610 R14: 0000000000000000 R15: 0000000000000000

Uninit was created at:
 kmsan_save_stack_with_flags mm/kmsan/kmsan.c:121 [inline]
 kmsan_internal_poison_shadow+0x5c/0xf0 mm/kmsan/kmsan.c:104
 kmsan_slab_alloc+0x8d/0xe0 mm/kmsan/kmsan_hooks.c:76
 slab_alloc_node mm/slub.c:2906 [inline]
 __kmalloc_node_track_caller+0xc61/0x15f0 mm/slub.c:4512
 __kmalloc_reserve net/core/skbuff.c:142 [inline]
 __alloc_skb+0x309/0xae0 net/core/skbuff.c:210
 alloc_skb include/linux/skbuff.h:1094 [inline]
 netlink_alloc_large_skb net/netlink/af_netlink.c:1176 [inline]
 netlink_sendmsg+0xdb8/0x1840 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:651 [inline]
 sock_sendmsg net/socket.c:671 [inline]
 ____sys_sendmsg+0xc7a/0x1240 net/socket.c:2353
 ___sys_sendmsg net/socket.c:2407 [inline]
 __sys_sendmmsg+0xa56/0x1060 net/socket.c:2497
 __do_sys_sendmmsg net/socket.c:2526 [inline]
 __se_sys_sendmmsg+0xbd/0xe0 net/socket.c:2523
 __x64_sys_sendmmsg+0x56/0x70 net/socket.c:2523
 do_syscall_64+0x9f/0x140 arch/x86/entry/common.c:48
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
=====================================================

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