Date:   Wed, 5 Apr 2023 19:41:38 +0900
From:   "Dae R. Jeong" <threeearcat@...il.com>
To:     edumazet@...gle.com, davem@...emloft.net, yoshfuji@...ux-ipv6.org,
        dsahern@...nel.org, kuba@...nel.org, pabeni@...hat.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        bpf@...r.kernel.org
Subject: KASAN: use-after-free Read in tcp_write_timer_handler

Hi,

We observed an issue "KASAN: use-after-free Read in tcp_write_timer_handler" during fuzzing.

Unfortunately, we have not found a reproducer for the crash yet. We
will inform you if we have any update on this crash.  Detailed crash
information is attached below.

Best regards,
Dae R. Jeong

-----
- Kernel version:
6.0-rc7

- Crash report:
==================================================================
BUG: KASAN: use-after-free in tcp_probe_timer net/ipv4/tcp_timer.c:378 [inline]
BUG: KASAN: use-after-free in tcp_write_timer_handler+0x921/0xa60 net/ipv4/tcp_timer.c:624
Read of size 1 at addr ffff888046bc86a5 by task syz-fuzzer/6625

CPU: 0 PID: 6625 Comm: syz-fuzzer Not tainted 6.0.0-rc7-00167-g92162e4a9862 #2
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1cf/0x2b7 lib/dump_stack.c:106
 print_address_description+0x21/0x470 mm/kasan/report.c:317
 print_report+0x108/0x1f0 mm/kasan/report.c:433
 kasan_report+0xe5/0x110 mm/kasan/report.c:495
 tcp_probe_timer net/ipv4/tcp_timer.c:378 [inline]
 tcp_write_timer_handler+0x921/0xa60 net/ipv4/tcp_timer.c:624
 tcp_write_timer+0x1a5/0x2c0 net/ipv4/tcp_timer.c:637
 call_timer_fn+0xf6/0x220 kernel/time/timer.c:1474
 expire_timers kernel/time/timer.c:1519 [inline]
 __run_timers+0x76f/0x980 kernel/time/timer.c:1790
 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1803
 __do_softirq+0x372/0x783 kernel/softirq.c:571
 __irq_exit_rcu+0xcf/0x160 kernel/softirq.c:650
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:662
 sysvec_apic_timer_interrupt+0x43/0xb0 arch/x86/kernel/apic/apic.c:1106
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:649
RIP: 0033:0x421fb1
Code: 90 48 8b 4f 18 90 49 b8 00 00 00 00 00 80 00 00 49 01 c8 49 c1 e8 1a 66 90 49 81 f8 00 00 40 00 0f 83 e2 00 00 00 4a 8b 14 c2 <84> 02 49 89 c8 48 c1 e9 10 81 e1 ff 03 00 00 44 0f b6 8c 0a 00 04
RSP: 002b:00007f3d50bebd38 EFLAGS: 00000287
RAX: 000000c001a0d140 RBX: 000000c001bba000 RCX: 000000c001a0c000
RDX: 00007f3d51bef000 RSI: 000000c000025240 RDI: 00007f3d791daa28
RBP: 00007f3d50bebd78 R08: 0000000000203000 R09: 00007f3d4c2f6001
R10: 000000000000008a R11: 0000000000004048 R12: 0000000000000004
R13: 000000c001a0d140 R14: 000000c000007520 R15: 0000000000000180
 </TASK>

Allocated by task 6664:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:437 [inline]
 __kasan_slab_alloc+0xa3/0xd0 mm/kasan/common.c:470
 kasan_slab_alloc include/linux/kasan.h:224 [inline]
 slab_post_alloc_hook mm/slab.h:727 [inline]
 slab_alloc_node mm/slub.c:3248 [inline]
 slab_alloc mm/slub.c:3256 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3263 [inline]
 kmem_cache_alloc+0x2e6/0x450 mm/slub.c:3273
 kmem_cache_zalloc include/linux/slab.h:723 [inline]
 net_alloc net/core/net_namespace.c:404 [inline]
 copy_net_ns+0x193/0x6d0 net/core/net_namespace.c:459
 create_new_namespaces+0x4db/0xa40 kernel/nsproxy.c:110
 unshare_nsproxy_namespaces+0x11e/0x180 kernel/nsproxy.c:226
 ksys_unshare+0x5a9/0xbc0 kernel/fork.c:3183
 __do_sys_unshare kernel/fork.c:3254 [inline]
 __se_sys_unshare kernel/fork.c:3252 [inline]
 __x64_sys_unshare+0x34/0x40 kernel/fork.c:3252
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4e/0xa0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Freed by task 6874:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x3d/0x60 mm/kasan/common.c:45
 kasan_set_free_info+0x1f/0x40 mm/kasan/generic.c:370
 ____kasan_slab_free+0x134/0x1c0 mm/kasan/common.c:367
 kasan_slab_free include/linux/kasan.h:200 [inline]
 slab_free_hook mm/slub.c:1759 [inline]
 slab_free_freelist_hook+0x278/0x370 mm/slub.c:1785
 slab_free mm/slub.c:3539 [inline]
 kmem_cache_free+0x11a/0x310 mm/slub.c:3556
 net_free net/core/net_namespace.c:433 [inline]
 cleanup_net+0xd68/0xe20 net/core/net_namespace.c:616
 process_one_work+0x83f/0x11a0 kernel/workqueue.c:2289
 worker_thread+0xa6c/0x1290 kernel/workqueue.c:2436
 kthread+0x28a/0x320 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306

Last potentially related work creation:
 kasan_save_stack+0x2b/0x50 mm/kasan/common.c:38
 __kasan_record_aux_stack+0xac/0xc0 mm/kasan/generic.c:348
 insert_work+0x54/0x400 kernel/workqueue.c:1358
 __queue_work+0xa95/0xe00 kernel/workqueue.c:1517
 call_timer_fn+0xf6/0x220 kernel/time/timer.c:1474
 expire_timers kernel/time/timer.c:1514 [inline]
 __run_timers+0x7a2/0x980 kernel/time/timer.c:1790
 __do_softirq+0x372/0x783 kernel/softirq.c:571

Second to last potentially related work creation:
 kasan_save_stack+0x2b/0x50 mm/kasan/common.c:38
 __kasan_record_aux_stack+0xac/0xc0 mm/kasan/generic.c:348
 insert_work+0x54/0x400 kernel/workqueue.c:1358
 __queue_work+0xa95/0xe00 kernel/workqueue.c:1517
 call_timer_fn+0xf6/0x220 kernel/time/timer.c:1474
 expire_timers kernel/time/timer.c:1514 [inline]
 __run_timers+0x7a2/0x980 kernel/time/timer.c:1790
 __do_softirq+0x372/0x783 kernel/softirq.c:571

The buggy address belongs to the object at ffff888046bc8000
 which belongs to the cache net_namespace of size 6784
The buggy address is located 1701 bytes inside of
 6784-byte region [ffff888046bc8000, ffff888046bc9a80)

The buggy address belongs to the physical page:
page:ffffea00011af200 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x46bc8
head:ffffea00011af200 order:3 compound_mapcount:0 compound_pincount:0
flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000010200 0000000000000000 dead000000000122 ffff888013618f00
raw: 0000000000000000 0000000080040004 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 6664, tgid 6664 (syz-executor.0), ts 88505587135, free_ts 0
 prep_new_page mm/page_alloc.c:2532 [inline]
 get_page_from_freelist+0x800/0xc10 mm/page_alloc.c:4283
 __alloc_pages+0x2f0/0x650 mm/page_alloc.c:5549
 alloc_slab_page mm/slub.c:1829 [inline]
 allocate_slab+0x1eb/0xc00 mm/slub.c:1974
 new_slab mm/slub.c:2034 [inline]
 ___slab_alloc+0x581/0xff0 mm/slub.c:3036
 __slab_alloc mm/slub.c:3123 [inline]
 slab_alloc_node mm/slub.c:3214 [inline]
 slab_alloc mm/slub.c:3256 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3263 [inline]
 kmem_cache_alloc+0x386/0x450 mm/slub.c:3273
 kmem_cache_zalloc include/linux/slab.h:723 [inline]
 net_alloc net/core/net_namespace.c:404 [inline]
 copy_net_ns+0x193/0x6d0 net/core/net_namespace.c:459
 create_new_namespaces+0x4db/0xa40 kernel/nsproxy.c:110
 unshare_nsproxy_namespaces+0x11e/0x180 kernel/nsproxy.c:226
 ksys_unshare+0x5a9/0xbc0 kernel/fork.c:3183
 __do_sys_unshare kernel/fork.c:3254 [inline]
 __se_sys_unshare kernel/fork.c:3252 [inline]
 __x64_sys_unshare+0x34/0x40 kernel/fork.c:3252
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4e/0xa0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
page_owner free stack trace missing

Memory state around the buggy address:
 ffff888046bc8580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888046bc8600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888046bc8680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                               ^
 ffff888046bc8700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888046bc8780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

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