KASAN: use-after-free Write in xp_put_pool

From: syzbot
Date: Wed Sep 02 2020 - 02:57:38 EST

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@xxxxxxxxx>
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@xxxxxxxxxxxxxxxxxxxxxxxxx
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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