Messages in this thread Patch in this message | | | From | Dongliang Mu <> | Date | Wed, 8 Feb 2023 17:01:48 +0800 | Subject | Re: [PATCH] nfc: llcp: Fix race in handling llcp_devices |
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On Tue, Nov 29, 2022 at 5:46 PM 'Wang ShaoBo' via syzkaller-bugs <syzkaller-bugs@googlegroups.com> wrote: > > There are multiple path operate llcp_devices list without protection: > > CPU0 CPU1 > > nfc_unregister_device() nfc_register_device() > nfc_llcp_unregister_device() nfc_llcp_register_device() //no lock > ... list_add(local->list, llcp_devices) > local_release() > list_del(local->list) > > CPU2 > ... > nfc_llcp_find_local() > list_for_each_entry(,&llcp_devices,) > > So reach race condition if two of the three occur simultaneously like > following crash report, although there is no reproduction script in > syzbot currently, our artificially constructed use cases can also > reproduce it: > > list_del corruption. prev->next should be ffff888060ce7000, but was ffff88802a0ad000. (prev=ffffffff8e536240) > ------------[ cut here ]------------ > kernel BUG at lib/list_debug.c:59! > invalid opcode: 0000 [#1] PREEMPT SMP KASAN > CPU: 0 PID: 16622 Comm: syz-executor.5 Not tainted 6.1.0-rc6-next-20221125-syzkaller #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022 > RIP: 0010:__list_del_entry_valid.cold+0x12/0x72 lib/list_debug.c:59 > Code: f0 ff 0f 0b 48 89 f1 48 c7 c7 60 96 a6 8a 4c 89 e6 e8 4b 29 f0 ff 0f 0b 4c 89 e1 48 89 ee 48 c7 c7 c0 98 a6 8a e8 37 29 f0 ff <0f> 0b 48 89 ee 48 c7 c7 a0 97 a6 8a e8 26 29 f0 ff 0f 0b 4c 89 e2 > RSP: 0018:ffffc900151afd58 EFLAGS: 00010282 > RAX: 000000000000006d RBX: 0000000000000001 RCX: 0000000000000000 > RDX: ffff88801e7eba80 RSI: ffffffff8166001c RDI: fffff52002a35f9d > RBP: ffff888060ce7000 R08: 000000000000006d R09: 0000000000000000 > R10: 0000000080000000 R11: 0000000000000000 R12: ffffffff8e536240 > R13: ffff88801f3f3000 R14: ffff888060ce1000 R15: ffff888079d855f0 > FS: 0000555556f57400(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 00007f095d5ad988 CR3: 000000002155a000 CR4: 00000000003506f0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > <TASK> > __list_del_entry include/linux/list.h:134 [inline] > list_del include/linux/list.h:148 [inline] > local_release net/nfc/llcp_core.c:171 [inline] > kref_put include/linux/kref.h:65 [inline] > nfc_llcp_local_put net/nfc/llcp_core.c:181 [inline] > nfc_llcp_local_put net/nfc/llcp_core.c:176 [inline] > nfc_llcp_unregister_device+0xb8/0x260 net/nfc/llcp_core.c:1619 > nfc_unregister_device+0x196/0x330 net/nfc/core.c:1179 > virtual_ncidev_close+0x52/0xb0 drivers/nfc/virtual_ncidev.c:163 > __fput+0x27c/0xa90 fs/file_table.c:320 > task_work_run+0x16f/0x270 kernel/task_work.c:179 > resume_user_mode_work include/linux/resume_user_mode.h:49 [inline] > exit_to_user_mode_loop kernel/entry/common.c:171 [inline] > exit_to_user_mode_prepare+0x23c/0x250 kernel/entry/common.c:203 > __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline] > syscall_exit_to_user_mode+0x1d/0x50 kernel/entry/common.c:296 > do_syscall_64+0x46/0xb0 arch/x86/entry/common.c:86 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > This patch add specific mutex lock llcp_devices_list_lock to ensure > handling llcp_devices list safety. > > Fixes: 30cc4587659e ("NFC: Move LLCP code to the NFC top level diirectory") > Reported-by: syzbot+81232c4a81a886e2b580@syzkaller.appspotmail.com
There is another syzbot bug report [1] contributed by the same bug. It has the syz reproducer. A patch testing has been deployed on the syzbot dashboard.
Besides, I have a doubt about this patch. This patch adds a mutex lock to make list operations(add, delete, find etc.) exclusive. If the following thread interleaving occurs, will this patch work?
CPU0 CPU2 nfc_llcp_unregister_device nfc_llcp_unregister_device ...... nfc_llcp_find_local local_release ...... list_del ...... local_cleanup local_llcp_local_put
If nfc_llcp_find_local executes before list deletion, it will still lead to double free and UAF. Please correct me if I make any mistakes. Thanks in advance.
[1] https://syzkaller.appspot.com/bug?id=41d9ed9b6dcd7b7c5611ed5eb64835b1a554e998
> Signed-off-by: Wang ShaoBo <bobo.shaobowang@huawei.com> > --- > net/nfc/llcp_core.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/net/nfc/llcp_core.c b/net/nfc/llcp_core.c > index 3364caabef8b..7deaecd9d3cd 100644 > --- a/net/nfc/llcp_core.c > +++ b/net/nfc/llcp_core.c > @@ -17,6 +17,7 @@ > static u8 llcp_magic[3] = {0x46, 0x66, 0x6d}; > > static LIST_HEAD(llcp_devices); > +static DEFINE_MUTEX(llcp_devices_list_lock); > > static void nfc_llcp_rx_skb(struct nfc_llcp_local *local, struct sk_buff *skb); > > @@ -168,7 +169,9 @@ static void local_release(struct kref *ref) > > local = container_of(ref, struct nfc_llcp_local, ref); > > + mutex_lock(&llcp_devices_list_lock); > list_del(&local->list); > + mutex_unlock(&llcp_devices_list_lock); > local_cleanup(local); > kfree(local); > } > @@ -282,9 +285,13 @@ struct nfc_llcp_local *nfc_llcp_find_local(struct nfc_dev *dev) > { > struct nfc_llcp_local *local; > > + mutex_lock(&llcp_devices_list_lock); > list_for_each_entry(local, &llcp_devices, list) > - if (local->dev == dev) > + if (local->dev == dev) { > + mutex_unlock(&llcp_devices_list_lock); > return local; > + } > + mutex_unlock(&llcp_devices_list_lock); > > pr_debug("No device found\n"); > > @@ -1600,7 +1607,9 @@ int nfc_llcp_register_device(struct nfc_dev *ndev) > timer_setup(&local->sdreq_timer, nfc_llcp_sdreq_timer, 0); > INIT_WORK(&local->sdreq_timeout_work, nfc_llcp_sdreq_timeout_work); > > + mutex_lock(&llcp_devices_list_lock); > list_add(&local->list, &llcp_devices); > + mutex_unlock(&llcp_devices_list_lock); > > return 0; > } > -- > 2.25.1 > > -- > You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group. > To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@googlegroups.com. > To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/20221129094436.3975668-1-bobo.shaobowang%40huawei.com.
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