KASAN: null-ptr-deref Write in dst

KASAN: null-ptr-deref Write in dst_release (3)
Status: internal: reported on 2021/12/16 07:16
Reported-by: syzbot+@syzkaller.appspotmail.com
Fix commit: e28587cc491e sit: do not call ipip6_dev_free() from sit_init_net()
Patched on: [ci-qemu-upstream ci-qemu-upstream-386 ci-qemu2-arm32 ci-qemu2-arm64 ci-qemu2-arm64-compat ci-qemu2-arm64-mte ci-upstream-bpf-kasan-gce ci-upstream-bpf-next-kasan-gce ci-upstream-gce-leak ci-upstream-kasan-gce ci-upstream-kasan-gce-386 ci-upstream-kasan-gce-root ci-upstream-kasan-gce-selinux-root ci-upstream-kasan-gce-smack-root ci-upstream-linux-next-kasan-gce-root ci-upstream-net-kasan-gce ci-upstream-net-this-kasan-gce ci2-upstream-kcsan-gce ci2-upstream-usb], missing on: [ci-qemu2-riscv64 ci-upstream-kmsan-gce ci-upstream-kmsan-gce-386]
First crash: 39d, last: 39d

similar bugs (3):
Kernel	Title	Repro	Cause bisect	Count	Last	Reported	Patched	Status
upstream	KASAN: null-ptr-deref Write in dst_release (2)	syz	error	148	44d	294d	0/22	closed as invalid on 2021/12/14 20:12
upstream	KASAN: null-ptr-deref Write in dst_release			27	951d	1113d	0/22	auto-closed as invalid on 2019/10/25 08:50
upstream	KASAN: user-memory-access Write in dst_release			18	955d	1113d	0/22	auto-closed as invalid on 2019/10/25 08:49

Sample crash report:

==================================================================
BUG: KASAN: null-ptr-deref in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
BUG: KASAN: null-ptr-deref in atomic_dec_return include/linux/atomic/atomic-instrumented.h:251 [inline]
BUG: KASAN: null-ptr-deref in dst_release net/core/dst.c:172 [inline]
BUG: KASAN: null-ptr-deref in dst_release+0x26/0xe0 net/core/dst.c:167
Write of size 4 at addr 0000000000000240 by task syz-executor.3/25939

CPU: 1 PID: 25939 Comm: syz-executor.3 Not tainted 5.16.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
 __kasan_report mm/kasan/report.c:437 [inline]
 kasan_report.cold+0x66/0xdf mm/kasan/report.c:450
 check_region_inline mm/kasan/generic.c:183 [inline]
 kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189
 instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
 atomic_dec_return include/linux/atomic/atomic-instrumented.h:251 [inline]
 dst_release net/core/dst.c:172 [inline]
 dst_release+0x26/0xe0 net/core/dst.c:167
 dst_cache_destroy net/core/dst_cache.c:160 [inline]
 dst_cache_destroy+0xcb/0x190 net/core/dst_cache.c:152
 ipip6_dev_free net/ipv6/sit.c:1414 [inline]
 sit_init_net+0x7d8/0xaa0 net/ipv6/sit.c:1936
 ops_init+0xaf/0x470 net/core/net_namespace.c:140
 setup_net+0x40f/0xa30 net/core/net_namespace.c:326
 copy_net_ns+0x318/0x760 net/core/net_namespace.c:470
 create_new_namespaces+0x3f6/0xb20 kernel/nsproxy.c:110
 unshare_nsproxy_namespaces+0xc1/0x1f0 kernel/nsproxy.c:226
 ksys_unshare+0x445/0x920 kernel/fork.c:3075
 __do_sys_unshare kernel/fork.c:3146 [inline]
 __se_sys_unshare kernel/fork.c:3144 [inline]
 __x64_sys_unshare+0x2d/0x40 kernel/fork.c:3144
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f0931baae99
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f0930520168 EFLAGS: 00000246 ORIG_RAX: 0000000000000110
RAX: ffffffffffffffda RBX: 00007f0931cbdf60 RCX: 00007f0931baae99
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000060000000
RBP: 00007f0931c04ff1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f09321f1b1f R14: 00007f0930520300 R15: 0000000000022000
 </TASK>
==================================================================

Crashes (2):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	VM info	Title
ci-upstream-kasan-gce	2021/12/16 07:15	upstream	2b14864acbaa	572bcb40	.config	log	report			info	KASAN: null-ptr-deref Write in dst_release
ci-upstream-net-this-kasan-gce	2021/12/16 14:25	net	ef8a0f6eab1c	8dd6a5e3	.config	log	report			info	KASAN: user-memory-access Write in dst_release