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Date:   Tue, 01 Sep 2020 23:57:22 -0700
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Subject: KASAN: use-after-free Write in xp_put_pool
From:   syzbot <syzbot+5334f62e4d22804e646a@syzkaller.appspotmail.com>
To:     akpm@linux-foundation.org, andriin@fb.com, ast@kernel.org,
        bjorn.topel@intel.com, bpf@vger.kernel.org, daniel@iogearbox.net,
        davem@davemloft.net, hawk@kernel.org, john.fastabend@gmail.com,
        jonathan.lemon@gmail.com, kafai@fb.com, kpsingh@chromium.org,
        kuba@kernel.org, linux-kernel@vger.kernel.org,
        magnus.karlsson@intel.com, mingo@kernel.org,
        netdev@vger.kernel.org, paulmck@kernel.org, peterz@infradead.org,
        songliubraving@fb.com, syzkaller-bugs@googlegroups.com,
        tglx@linutronix.de, yhs@fb.com
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Sender: linux-kernel-owner@vger.kernel.org
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Hello,

syzbot found the following issue on:

HEAD commit:    dc1a9bf2 octeontx2-pf: Add UDP segmentation offload support
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=16ff67de900000
kernel config:  https://syzkaller.appspot.com/x/.config?x=b6856d16f78d8fa9
dashboard link: https://syzkaller.appspot.com/bug?extid=5334f62e4d22804e646a
compiler:       gcc (GCC) 10.1.0-syz 20200507
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12e9f279900000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=125f3e1e900000

The issue was bisected to:

commit a1132430c2c55af62d13e9fca752d46f14d548b3
Author: Magnus Karlsson <magnus.karlsson@intel.com>
Date:   Fri Aug 28 08:26:26 2020 +0000

    xsk: Add shared umem support between devices

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=10a373de900000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=12a373de900000
console output: https://syzkaller.appspot.com/x/log.txt?x=14a373de900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5334f62e4d22804e646a@syzkaller.appspotmail.com
Fixes: a1132430c2c5 ("xsk: Add shared umem support between devices")

==================================================================
BUG: KASAN: use-after-free in instrument_atomic_write include/linux/instrumented.h:71 [inline]
BUG: KASAN: use-after-free in atomic_fetch_sub_release include/asm-generic/atomic-instrumented.h:220 [inline]
BUG: KASAN: use-after-free in refcount_sub_and_test include/linux/refcount.h:266 [inline]
BUG: KASAN: use-after-free in refcount_dec_and_test include/linux/refcount.h:294 [inline]
BUG: KASAN: use-after-free in xp_put_pool+0x2c/0x1e0 net/xdp/xsk_buff_pool.c:262
Write of size 4 at addr ffff8880a6a4d860 by task ksoftirqd/0/9

CPU: 0 PID: 9 Comm: ksoftirqd/0 Not tainted 5.9.0-rc1-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+0x18f/0x20d lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
 check_memory_region_inline mm/kasan/generic.c:186 [inline]
 check_memory_region+0x13d/0x180 mm/kasan/generic.c:192
 instrument_atomic_write include/linux/instrumented.h:71 [inline]
 atomic_fetch_sub_release include/asm-generic/atomic-instrumented.h:220 [inline]
 refcount_sub_and_test include/linux/refcount.h:266 [inline]
 refcount_dec_and_test include/linux/refcount.h:294 [inline]
 xp_put_pool+0x2c/0x1e0 net/xdp/xsk_buff_pool.c:262
 xsk_destruct+0x7d/0xa0 net/xdp/xsk.c:1138
 __sk_destruct+0x4b/0x860 net/core/sock.c:1764
 rcu_do_batch kernel/rcu/tree.c:2428 [inline]
 rcu_core+0x5c7/0x1190 kernel/rcu/tree.c:2656
 __do_softirq+0x2de/0xa24 kernel/softirq.c:298
 run_ksoftirqd kernel/softirq.c:652 [inline]
 run_ksoftirqd+0x89/0x100 kernel/softirq.c:644
 smpboot_thread_fn+0x655/0x9e0 kernel/smpboot.c:165
 kthread+0x3b5/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

Allocated by task 6854:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
 kasan_set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:461
 kmalloc_node include/linux/slab.h:577 [inline]
 kvmalloc_node+0x61/0xf0 mm/util.c:574
 kvmalloc include/linux/mm.h:750 [inline]
 kvzalloc include/linux/mm.h:758 [inline]
 xp_create_and_assign_umem+0x58/0x8d0 net/xdp/xsk_buff_pool.c:54
 xsk_bind+0x9a0/0xed0 net/xdp/xsk.c:709
 __sys_bind+0x1e9/0x250 net/socket.c:1656
 __do_sys_bind net/socket.c:1667 [inline]
 __se_sys_bind net/socket.c:1665 [inline]
 __x64_sys_bind+0x6f/0xb0 net/socket.c:1665
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 6854:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
 kasan_set_track+0x1c/0x30 mm/kasan/common.c:56
 kasan_set_free_info+0x1b/0x30 mm/kasan/generic.c:355
 __kasan_slab_free+0xd8/0x120 mm/kasan/common.c:422
 __cache_free mm/slab.c:3418 [inline]
 kfree+0x103/0x2c0 mm/slab.c:3756
 kvfree+0x42/0x50 mm/util.c:603
 xp_destroy net/xdp/xsk_buff_pool.c:44 [inline]
 xp_destroy+0x45/0x60 net/xdp/xsk_buff_pool.c:38
 xsk_bind+0xbdd/0xed0 net/xdp/xsk.c:719
 __sys_bind+0x1e9/0x250 net/socket.c:1656
 __do_sys_bind net/socket.c:1667 [inline]
 __se_sys_bind net/socket.c:1665 [inline]
 __x64_sys_bind+0x6f/0xb0 net/socket.c:1665
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff8880a6a4d800
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 96 bytes inside of
 1024-byte region [ffff8880a6a4d800, ffff8880a6a4dc00)
The buggy address belongs to the page:
page:00000000dd5fc18f refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0xa6a4d
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea00029cce48 ffffea00025f2148 ffff8880aa040700
raw: 0000000000000000 ffff8880a6a4d000 0000000100000002 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a6a4d700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880a6a4d780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880a6a4d800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                       ^
 ffff8880a6a4d880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880a6a4d900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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For information about bisection process see: https://goo.gl/tpsmEJ#bisection
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