Messages in this thread | | | From | Dmitry Vyukov <> | Date | Tue, 15 Nov 2022 10:35:40 +0100 | Subject | Re: [syzbot] possible deadlock in nci_set_local_general_bytes |
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On Tue, 15 Nov 2022 at 10:18, Hillf Danton <hdanton@sina.com> wrote: > > On 14 Nov 2022 09:43:48 -0800 > > syzbot found the following issue on: > > > > HEAD commit: 1621b6eaebf7 Merge branch 'for-next/fixes' into for-kernelci > > git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci > > console output: https://syzkaller.appspot.com/x/log.txt?x=119413e1880000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=606e57fd25c5c6cc > > dashboard link: https://syzkaller.appspot.com/bug?extid=8768e9ec924b08e63f82 > > userspace arch: arm64 > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1097e935880000 > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=177b5b15880000 > > In the open path, register nci device without mci_mutex held in bid to break > the lock chain.
This should be fixed by the following commit when/if it's merged. The commit removes nci_mutex.
nfc: Allow to create multiple virtual nci devices https://lore.kernel.org/all/20221104170422.979558-1-dvyukov@google.com/
> #syz test https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git 1621b6eaebf7 > > --- x/drivers/nfc/virtual_ncidev.c > +++ y/drivers/nfc/virtual_ncidev.c > @@ -15,6 +15,7 @@ > > enum virtual_ncidev_mode { > virtual_ncidev_enabled, > + virtual_ncidev_enabling, > virtual_ncidev_disabled, > virtual_ncidev_disabling, > }; > @@ -128,6 +129,7 @@ static ssize_t virtual_ncidev_write(stru > > static int virtual_ncidev_open(struct inode *inode, struct file *file) > { > + struct nci_dev *new; > int ret = 0; > > mutex_lock(&nci_mutex); > @@ -135,24 +137,27 @@ static int virtual_ncidev_open(struct in > mutex_unlock(&nci_mutex); > return -EBUSY; > } > + state = virtual_ncidev_enabling; > + mutex_unlock(&nci_mutex); > > - ndev = nci_allocate_device(&virtual_nci_ops, VIRTUAL_NFC_PROTOCOLS, > - 0, 0); > - if (!ndev) { > - mutex_unlock(&nci_mutex); > - return -ENOMEM; > + ret = -ENOMEM; > + new = nci_allocate_device(&virtual_nci_ops, VIRTUAL_NFC_PROTOCOLS, 0, 0); > + if (new) { > + ret = nci_register_device(new); > + if (ret) > + nci_free_device(new); > } > > - ret = nci_register_device(ndev); > - if (ret < 0) { > - nci_free_device(ndev); > - mutex_unlock(&nci_mutex); > - return ret; > + mutex_lock(&nci_mutex); > + if (ret) > + state = virtual_ncidev_disabled; > + else { > + ndev = new; > + state = virtual_ncidev_enabled; > } > - state = virtual_ncidev_enabled; > mutex_unlock(&nci_mutex); > > - return 0; > + return ret; > } > > static int virtual_ncidev_close(struct inode *inode, struct file *file) > @@ -167,9 +172,9 @@ static int virtual_ncidev_close(struct i > nci_free_device(ndev); > > mutex_lock(&nci_mutex); > + state = virtual_ncidev_disabled; > } > > - state = virtual_ncidev_disabled; > mutex_unlock(&nci_mutex); > > return 0; > -- > > -- > 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/20221115091825.2381-1-hdanton%40sina.com.
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