KASAN: slab-out-of-bounds Read in _decode_session6 (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3f8a27f9e27b Linux 4.19.211
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=114623bf080000
kernel config: https://syzkaller.appspot.com/x/.config?x=9b9277b418617afe
dashboard link: https://syzkaller.appspot.com/bug?extid=0a18990fbcb6358fdd1e
compiler: gcc version 10.2.1 20210110 (Debian 10.2.1-6)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=149b515f080000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15b92980880000

Downloadable assets:
disk image: https://storage.googleapis.com/98c0bdb4abb3/disk-3f8a27f9.raw.xz
vmlinux: https://storage.googleapis.com/ea228ff02669/vmlinux-3f8a27f9.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0a1899...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-out-of-bounds in _decode_session6+0xf56/0x1370 net/ipv6/xfrm6_policy.c:137
Read of size 1 at addr ffff8880b27cda96 by task swapper/0/0

CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.19.211-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/26/2022
Call Trace:
<IRQ>
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1fc/0x2ef lib/dump_stack.c:118
print_address_description.cold+0x54/0x219 mm/kasan/report.c:256
kasan_report_error.cold+0x8a/0x1b9 mm/kasan/report.c:354
kasan_report mm/kasan/report.c:412 [inline]
__asan_report_load1_noabort+0x88/0x90 mm/kasan/report.c:430
_decode_session6+0xf56/0x1370 net/ipv6/xfrm6_policy.c:137
__xfrm_decode_session+0x5a/0x130 net/xfrm/xfrm_policy.c:2299
xfrm_decode_session include/net/xfrm.h:1238 [inline]
vti_tunnel_xmit+0x279/0x1850 net/ipv4/ip_vti.c:326
__netdev_start_xmit include/linux/netdevice.h:4349 [inline]
netdev_start_xmit include/linux/netdevice.h:4363 [inline]
xmit_one net/core/dev.c:3256 [inline]
dev_hard_start_xmit+0x1a8/0x920 net/core/dev.c:3272
sch_direct_xmit+0x2d6/0xf70 net/sched/sch_generic.c:332
qdisc_restart net/sched/sch_generic.c:395 [inline]
__qdisc_run+0x4d0/0x1640 net/sched/sch_generic.c:403
__dev_xmit_skb net/core/dev.c:3500 [inline]
__dev_queue_xmit+0x1518/0x2e00 net/core/dev.c:3807
neigh_output include/net/neighbour.h:501 [inline]
ip6_finish_output2+0x113d/0x2290 net/ipv6/ip6_output.c:120
ip6_finish_output+0x89b/0x10f0 net/ipv6/ip6_output.c:192
NF_HOOK_COND include/linux/netfilter.h:278 [inline]
ip6_output+0x205/0x770 net/ipv6/ip6_output.c:209
dst_output include/net/dst.h:455 [inline]
NF_HOOK include/linux/netfilter.h:289 [inline]
ndisc_send_skb+0xa24/0x1720 net/ipv6/ndisc.c:491
ndisc_send_rs+0x131/0x690 net/ipv6/ndisc.c:685
addrconf_rs_timer+0x384/0x6a0 net/ipv6/addrconf.c:3835
call_timer_fn+0x177/0x700 kernel/time/timer.c:1338
expire_timers+0x243/0x4e0 kernel/time/timer.c:1375
__run_timers kernel/time/timer.c:1696 [inline]
run_timer_softirq+0x21c/0x670 kernel/time/timer.c:1709
__do_softirq+0x265/0x980 kernel/softirq.c:292
invoke_softirq kernel/softirq.c:372 [inline]
irq_exit+0x215/0x260 kernel/softirq.c:412
exiting_irq arch/x86/include/asm/apic.h:536 [inline]
smp_apic_timer_interrupt+0x136/0x550 arch/x86/kernel/apic/apic.c:1098
apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:894
</IRQ>
RIP: 0010:native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:61
Code: 48 89 df e8 f4 20 7f f9 e9 2e ff ff ff 48 89 df e8 e7 20 7f f9 eb 82 90 90 90 90 90 e9 07 00 00 00 0f 00 2d 14 43 4e 00 fb f4 <c3> 90 e9 07 00 00 00 0f 00 2d 04 43 4e 00 f4 c3 90 90 41 56 41 55
RSP: 0018:ffffffff89e07d40 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff13
RAX: 1ffffffff13e3054 RBX: dffffc0000000000 RCX: 0000000000000000
RDX: dffffc0000000000 RSI: 0000000000000001 RDI: ffffffff89e78904
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff89f18290
R13: 1ffffffff13c0fb2 R14: 0000000000000000 R15: 0000000000000000
arch_safe_halt arch/x86/include/asm/paravirt.h:94 [inline]
default_idle+0x49/0x310 arch/x86/kernel/process.c:557
cpuidle_idle_call kernel/sched/idle.c:153 [inline]
do_idle+0x2ec/0x4b0 kernel/sched/idle.c:263
cpu_startup_entry+0xc5/0xe0 kernel/sched/idle.c:369
start_kernel+0x8d6/0x911 init/main.c:736
secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243

Allocated by task 4696:
kmem_cache_alloc+0x122/0x370 mm/slab.c:3559
getname_flags+0xce/0x590 fs/namei.c:140
getname fs/namei.c:211 [inline]
__do_sys_unlink fs/namei.c:4112 [inline]
__se_sys_unlink fs/namei.c:4110 [inline]
__x64_sys_unlink+0x31/0x50 fs/namei.c:4110
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 4696:
__cache_free mm/slab.c:3503 [inline]
kmem_cache_free+0x7f/0x260 mm/slab.c:3765
putname+0xe1/0x120 fs/namei.c:261
do_unlinkat+0x12b/0x660 fs/namei.c:4086
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8880b27cc2c0
which belongs to the cache names_cache of size 4096
The buggy address is located 2006 bytes to the right of
4096-byte region [ffff8880b27cc2c0, ffff8880b27cd2c0)
The buggy address belongs to the page:
page:ffffea0002c9f300 count:1 mapcount:0 mapping:ffff88823b843380 index:0x0 compound_mapcount: 0
flags: 0xfff00000008100(slab|head)
raw: 00fff00000008100 ffffea0002caca08 ffffea0002450008 ffff88823b843380
raw: 0000000000000000 ffff8880b27cc2c0 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8880b27cd980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8880b27cda00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880b27cda80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
^
ffff8880b27cdb00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8880b27cdb80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
----------------
Code disassembly (best guess):
0: 48 89 df mov %rbx,%rdi
3: e8 f4 20 7f f9 callq 0xf97f20fc
8: e9 2e ff ff ff jmpq 0xffffff3b
d: 48 89 df mov %rbx,%rdi
10: e8 e7 20 7f f9 callq 0xf97f20fc
15: eb 82 jmp 0xffffff99
17: 90 nop
18: 90 nop
19: 90 nop
1a: 90 nop
1b: 90 nop
1c: e9 07 00 00 00 jmpq 0x28
21: 0f 00 2d 14 43 4e 00 verw 0x4e4314(%rip) # 0x4e433c
28: fb sti
29: f4 hlt
* 2a: c3 retq <-- trapping instruction
2b: 90 nop
2c: e9 07 00 00 00 jmpq 0x38
31: 0f 00 2d 04 43 4e 00 verw 0x4e4304(%rip) # 0x4e433c
38: f4 hlt
39: c3 retq
3a: 90 nop
3b: 90 nop
3c: 41 56 push %r14
3e: 41 55 push %r13


---
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