[syzbot] [bpf?] [net?] WARNING: refcount bug in xp_put_pool

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d7b3af5a77e8 Add linux-next specific files for 20230728
git tree: linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=101a8319a80000
kernel config: https://syzkaller.appspot.com/x/.config?x=62dd327c382e3fe
dashboard link: https://syzkaller.appspot.com/bug?extid=8ada0057e69293a05fd4
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=146dbe31a80000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11656a7ea80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/5efa5e68267f/disk-d7b3af5a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b1f5d3e10263/vmlinux-d7b3af5a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/57cab469d186/bzImage-d7b3af5a.xz

The issue was bisected to:

commit 9f78bf330a66cd400b3e00f370f597e9fa939207
Author: Xuan Zhuo <xuan...@linux.alibaba.com>
Date: Thu Feb 16 08:30:47 2023 +0000

xsk: support use vaddr as ring

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=13541155a80000
final oops: https://syzkaller.appspot.com/x/report.txt?x=10d41155a80000
console output: https://syzkaller.appspot.com/x/log.txt?x=17541155a80000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8ada00...@syzkaller.appspotmail.com
Fixes: 9f78bf330a66 ("xsk: support use vaddr as ring")

------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 0 PID: 5078 at lib/refcount.c:28 refcount_warn_saturate+0x140/0x1f0 lib/refcount.c:28
Modules linked in:
CPU: 0 PID: 5078 Comm: kworker/0:3 Not tainted 6.5.0-rc3-next-20230728-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2023
Workqueue: events drain_vmap_area_work
RIP: 0010:refcount_warn_saturate+0x140/0x1f0 lib/refcount.c:28
Code: 0a 31 ff 89 de e8 f0 3e 65 fd 84 db 0f 85 6e ff ff ff e8 b3 43 65 fd 48 c7 c7 c0 33 c8 8a c6 05 64 ce 74 0a 01 e8 60 99 2b fd <0f> 0b e9 4f ff ff ff e8 94 43 65 fd 0f b6 1d 4a ce 74 0a 31 ff 89
RSP: 0018:ffffc90000007d88 EFLAGS: 00010286
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000100
RDX: ffff88807190d940 RSI: ffffffff814d5b56 RDI: 0000000000000001
RBP: ffff888071110460 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: ffff888071110460
R13: ffff8880710d24e8 R14: 0000000000000000 R15: 0000000000000000
FS: 0000000000000000(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000555557361650 CR3: 00000000476b6000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<IRQ>
__refcount_sub_and_test include/linux/refcount.h:283 [inline]
__refcount_dec_and_test include/linux/refcount.h:315 [inline]
refcount_dec_and_test include/linux/refcount.h:333 [inline]
xp_put_pool+0x8a/0x1e0 net/xdp/xsk_buff_pool.c:286
xsk_destruct+0x95/0x140 net/xdp/xsk.c:1601
__sk_destruct+0x4d/0x770 net/core/sock.c:2163
rcu_do_batch kernel/rcu/tree.c:2139 [inline]
rcu_core+0x7fb/0x1bb0 kernel/rcu/tree.c:2403
__do_softirq+0x218/0x965 kernel/softirq.c:553
invoke_softirq kernel/softirq.c:427 [inline]
__irq_exit_rcu kernel/softirq.c:632 [inline]
irq_exit_rcu+0xb7/0x120 kernel/softirq.c:644
common_interrupt+0xae/0xd0 arch/x86/kernel/irq.c:247
</IRQ>
<TASK>
asm_common_interrupt+0x26/0x40 arch/x86/include/asm/idtentry.h:636
RIP: 0010:stack_trace_consume_entry+0xaf/0x160 kernel/stacktrace.c:93
Code: c0 03 38 d0 7c 08 84 d2 0f 85 90 00 00 00 8b 43 0c 85 c0 75 53 48 b8 00 00 00 00 00 fc ff df 48 89 da 48 c1 ea 03 80 3c 02 00 <0f> 85 92 00 00 00 8d 45 01 89 43 10 48 8b 03 48 8d 2c e8 48 b8 00
RSP: 0018:ffffc90003d7f6d8 EFLAGS: 00000246
RAX: dffffc0000000000 RBX: ffffc90003d7f7b8 RCX: 0000000000000000
RDX: 1ffff920007afef7 RSI: ffffffff81cffbd8 RDI: ffffc90003d7f7c4
RBP: 0000000000000000 R08: ffffc90003d7f72c R09: ffffffff8f40e62e
R10: ffffc90003d7f6f8 R11: 000000000000e4d6 R12: ffffffff8174c470
R13: ffffc90003d7f7b8 R14: 0000000000000000 R15: ffff88807190d940
arch_stack_walk+0x7f/0xf0 arch/x86/kernel/stacktrace.c:27
stack_trace_save+0x96/0xd0 kernel/stacktrace.c:122
save_stack+0x160/0x1f0 mm/page_owner.c:128
__reset_page_owner+0x5a/0x190 mm/page_owner.c:149
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1160 [inline]
free_unref_page_prepare+0x508/0xb90 mm/page_alloc.c:2383
free_unref_page+0x33/0x3b0 mm/page_alloc.c:2478
kasan_depopulate_vmalloc_pte+0x63/0x80 mm/kasan/shadow.c:427
apply_to_pte_range mm/memory.c:2735 [inline]
apply_to_pmd_range mm/memory.c:2779 [inline]
apply_to_pud_range mm/memory.c:2815 [inline]
apply_to_p4d_range mm/memory.c:2851 [inline]
__apply_to_page_range+0x5ed/0xdb0 mm/memory.c:2885
kasan_release_vmalloc+0xa8/0xc0 mm/kasan/shadow.c:544
__purge_vmap_area_lazy+0x8b9/0x2160 mm/vmalloc.c:1770
drain_vmap_area_work+0x54/0xd0 mm/vmalloc.c:1804
process_one_work+0xaa2/0x16f0 kernel/workqueue.c:2603
worker_thread+0x687/0x1110 kernel/workqueue.c:2754
kthread+0x33a/0x430 kernel/kthread.c:389
ret_from_fork+0x2c/0x70 arch/x86/kernel/process.c:145
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304
</TASK>
----------------
Code disassembly (best guess), 2 bytes skipped:
0: 38 d0 cmp %dl,%al
2: 7c 08 jl 0xc
4: 84 d2 test %dl,%dl
6: 0f 85 90 00 00 00 jne 0x9c
c: 8b 43 0c mov 0xc(%rbx),%eax
f: 85 c0 test %eax,%eax
11: 75 53 jne 0x66
13: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax
1a: fc ff df
1d: 48 89 da mov %rbx,%rdx
20: 48 c1 ea 03 shr $0x3,%rdx
24: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1)
* 28: 0f 85 92 00 00 00 jne 0xc0 <-- trapping instruction
2e: 8d 45 01 lea 0x1(%rbp),%eax
31: 89 43 10 mov %eax,0x10(%rbx)
34: 48 8b 03 mov (%rbx),%rax
37: 48 8d 2c e8 lea (%rax,%rbp,8),%rbp
3b: 48 rex.W
3c: b8 .byte 0xb8


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

If the bug is already fixed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
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#syz undup

[Hillf Danton]

On Mon, 31 Jul 2023 00:57:58 -0700

> HEAD commit: d7b3af5a77e8 Add linux-next specific files for 20230728
> git tree: linux-next

> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11656a7ea80000

Check pool valid before putting it.

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git d7b3af5a77e8

--- x/net/xdp/xsk.c
+++ y/net/xdp/xsk.c
@@ -1188,6 +1188,7 @@ static int xsk_bind(struct socket *sock,
err = xp_alloc_tx_descs(xs->pool, xs);
if (err) {
xp_put_pool(xs->pool);
+ xs->pool = NULL;
sockfd_put(sock);
goto out_unlock;
}
@@ -1597,6 +1598,8 @@ static void xsk_destruct(struct sock *sk

if (!sock_flag(sk, SOCK_DEAD))
return;
+ if (!xs->pool)
+ return;

if (!xp_put_pool(xs->pool))
xdp_put_umem(xs->umem, !xs->pool);
--

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+8ada00...@syzkaller.appspotmail.com

Tested on:

commit: d7b3af5a Add linux-next specific files for 20230728
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
console output: https://syzkaller.appspot.com/x/log.txt?x=13353089a80000

kernel config: https://syzkaller.appspot.com/x/.config?x=62dd327c382e3fe
dashboard link: https://syzkaller.appspot.com/bug?extid=8ada0057e69293a05fd4
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=10318fcea80000

Note: testing is done by a robot and is best-effort only.

[syzbot]

> #syz test:

want 2 args (repo, branch), got 1

>
>

[syzbot]

> #syz test: https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git 999f6631866e9ea81add935b9c6ebaab0579d259

Your commands are accepted, but please keep syzkall...@googlegroups.com mailing list in CC next time. It serves as a history of what happened with each bug report. Thank you.

>
>

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+8ada00...@syzkaller.appspotmail.com

Tested on:

commit: 999f6631 Merge tag 'net-6.5-rc5' of git://git.kernel.o..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf.git
console output: https://syzkaller.appspot.com/x/log.txt?x=102be81da80000
kernel config: https://syzkaller.appspot.com/x/.config?x=e50aa0b20b962656

dashboard link: https://syzkaller.appspot.com/bug?extid=8ada0057e69293a05fd4
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=11d6c171a80000