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BUG: KASAN: slab-out-of-bounds in setup_udp_tunnel_sock+0x3a4/0x400 net/ipv4/udp_tunnel.c:78
Write of size 1 at addr ffff8880a4e9e590 by task syz-executor847/8915

CPU: 0 PID: 8915 Comm: syz-executor847 Not tainted 5.5.0-rc7-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+0x1fb/0x318 lib/dump_stack.c:118
 print_address_description+0x74/0x5c0 mm/kasan/report.c:374
 __kasan_report+0x149/0x1c0 mm/kasan/report.c:506
 kasan_report+0x26/0x50 mm/kasan/common.c:639
 __asan_report_store1_noabort+0x17/0x20 mm/kasan/generic_report.c:137
 setup_udp_tunnel_sock+0x3a4/0x400 net/ipv4/udp_tunnel.c:78
 gtp_encap_enable_socket+0x27b/0x340 drivers/net/gtp.c:827
 gtp_encap_enable drivers/net/gtp.c:845 [inline]
 gtp_newlink+0x81/0x1160 drivers/net/gtp.c:666
 __rtnl_newlink net/core/rtnetlink.c:3305 [inline]
 rtnl_newlink+0x143e/0x1c00 net/core/rtnetlink.c:3363
 rtnetlink_rcv_msg+0x889/0xd40 net/core/rtnetlink.c:5424
 netlink_rcv_skb+0x19e/0x3e0 net/netlink/af_netlink.c:2477
 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:5442
 netlink_unicast_kernel net/netlink/af_netlink.c:1302 [inline]
 netlink_unicast+0x767/0x920 net/netlink/af_netlink.c:1328
 netlink_sendmsg+0xa2c/0xd50 net/netlink/af_netlink.c:1917
 sock_sendmsg_nosec net/socket.c:639 [inline]
 sock_sendmsg net/socket.c:659 [inline]
 ____sys_sendmsg+0x4f7/0x7f0 net/socket.c:2330
 ___sys_sendmsg net/socket.c:2384 [inline]
 __sys_sendmsg+0x1ed/0x290 net/socket.c:2417
 __do_sys_sendmsg net/socket.c:2426 [inline]
 __se_sys_sendmsg net/socket.c:2424 [inline]
 __x64_sys_sendmsg+0x7f/0x90 net/socket.c:2424
 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4402b9
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:00007fff69c57b68 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004402b9
RDX: 0000000000000000 RSI: 0000000020000100 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 00000000004002c8 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401b40
R13: 0000000000401bd0 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 8915:
 save_stack mm/kasan/common.c:72 [inline]
 set_track mm/kasan/common.c:80 [inline]
 __kasan_kmalloc+0x118/0x1c0 mm/kasan/common.c:513
 kasan_slab_alloc+0xf/0x20 mm/kasan/common.c:521
 slab_post_alloc_hook mm/slab.h:584 [inline]
 slab_alloc mm/slab.c:3320 [inline]
 kmem_cache_alloc+0x1f5/0x2e0 mm/slab.c:3484
 sk_prot_alloc+0x60/0x290 net/core/sock.c:1597
 sk_alloc+0x38/0x9a0 net/core/sock.c:1657
 inet_create+0x5da/0xdb0 net/ipv4/af_inet.c:321
 __sock_create+0x5cb/0x910 net/socket.c:1420
 sock_create net/socket.c:1471 [inline]
 __sys_socket+0xe7/0x2e0 net/socket.c:1513
 __do_sys_socket net/socket.c:1522 [inline]
 __se_sys_socket net/socket.c:1520 [inline]
 __x64_sys_socket+0x7a/0x90 net/socket.c:1520
 do_syscall_64+0xf7/0x1c0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff8880a4e9e040
 which belongs to the cache RAW of size 1360
The buggy address is located 0 bytes to the right of
 1360-byte region [ffff8880a4e9e040, ffff8880a4e9e590)
The buggy address belongs to the page:
page:ffffea000293a780 refcount:1 mapcount:0 mapping:ffff8880a7bc8380 index:0x0 compound_mapcount: 0
raw: 00fffe0000010200 ffff8880a5328448 ffff8880a5328448 ffff8880a7bc8380
raw: 0000000000000000 ffff8880a4e9e040 0000000100000005 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a4e9e480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8880a4e9e500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8880a4e9e580: 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                         ^
 ffff8880a4e9e600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880a4e9e680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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