BUG: KASAN: use-after-free in ethnl_bitmap32_not_zero net/ethtool/bitset.c:112 [inline]
BUG: KASAN: use-after-free in ethnl_compact_sanity_checks net/ethtool/bitset.c:529 [inline]
BUG: KASAN: use-after-free in ethnl_update_bitset32.part.0+0x8db/0x1820 net/ethtool/bitset.c:572
Read of size 4 at addr ffff8880470df83c by task syz-executor.1/9365

CPU: 1 PID: 9365 Comm: syz-executor.1 Not tainted 5.6.0-rc2-syzkaller #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x197/0x210 lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
 __kasan_report.cold+0x1b/0x32 mm/kasan/report.c:506
 kasan_report+0x12/0x20 mm/kasan/common.c:641
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/generic_report.c:134
 ethnl_bitmap32_not_zero net/ethtool/bitset.c:112 [inline]
 ethnl_compact_sanity_checks net/ethtool/bitset.c:529 [inline]
 ethnl_update_bitset32.part.0+0x8db/0x1820 net/ethtool/bitset.c:572
 ethnl_update_bitset32 net/ethtool/bitset.c:562 [inline]
 ethnl_update_bitset+0x4d/0x67 net/ethtool/bitset.c:734
 ethnl_update_linkmodes net/ethtool/linkmodes.c:303 [inline]
 ethnl_set_linkmodes+0x461/0xc30 net/ethtool/linkmodes.c:357
 genl_family_rcv_msg_doit net/netlink/genetlink.c:672 [inline]
 genl_family_rcv_msg net/netlink/genetlink.c:717 [inline]
 genl_rcv_msg+0x67d/0xea0 net/netlink/genetlink.c:734
 netlink_rcv_skb+0x177/0x450 net/netlink/af_netlink.c:2478
 genl_rcv+0x29/0x40 net/netlink/genetlink.c:745
 netlink_unicast_kernel net/netlink/af_netlink.c:1303 [inline]
 netlink_unicast+0x59e/0x7e0 net/netlink/af_netlink.c:1329
 netlink_sendmsg+0x91c/0xea0 net/netlink/af_netlink.c:1918
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg+0xd7/0x130 net/socket.c:672
 ____sys_sendmsg+0x753/0x880 net/socket.c:2343
 ___sys_sendmsg+0x100/0x170 net/socket.c:2397
 __sys_sendmsg+0x105/0x1d0 net/socket.c:2430
 __compat_sys_sendmsg net/compat.c:642 [inline]
 __do_compat_sys_sendmsg net/compat.c:649 [inline]
 __se_compat_sys_sendmsg net/compat.c:646 [inline]
 __ia32_compat_sys_sendmsg+0x7a/0xb0 net/compat.c:646
 do_syscall_32_irqs_on arch/x86/entry/common.c:337 [inline]
 do_fast_syscall_32+0x27b/0xe16 arch/x86/entry/common.c:408
 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
RIP: 0023:0xf7f15e39
Code: 1d 00 00 00 89 d3 5b 5e 5d c3 8b 04 24 c3 8b 1c 24 c3 8b 3c 24 c3 90 90 90 90 90 90 90 90 90 90 90 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 002b:00000000f5d100bc EFLAGS: 00000296 ORIG_RAX: 0000000000000172
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000020000240
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

The buggy address belongs to the page:
page:ffffea00011c37c0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0x4fffe0000000000()
raw: 04fffe0000000000 ffffea00011c37c8 ffffea00011c37c8 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880470df700: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8880470df780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8880470df800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                        ^
 ffff8880470df880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8880470df900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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