Re: [PATCH] nbd: reclassify u->iolock of AF_UNIX sockets

[Christian Borntraeger <borntraeger@linux.ibm.com>]

Am 14.07.26 um 18:19 schrieb Christian Borntraeger:
> Am 13.07.26 um 20:14 schrieb Christian Borntraeger:
> 
> I just realized I had my kernel.org address in from.
> question is, is this the right fix and shall I do a proper patch wit correct from and signoff.
> 
> [..]
> 
>> diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
>> index 8f10762e90ef..a811e431b47a 100644
>> --- a/drivers/block/nbd.c
>> +++ b/drivers/block/nbd.c
>> @@ -32,6 +32,7 @@
>>   #include <linux/err.h>
>>   #include <linux/kernel.h>
>>   #include <linux/slab.h>
>> +#include <net/af_unix.h>
>>   #include <net/sock.h>
>>   #include <linux/net.h>
>>   #include <linux/kthread.h>
>> @@ -1241,6 +1242,7 @@ static struct socket *nbd_get_socket(struct nbd_device *nbd, unsigned long fd,
>>   #ifdef CONFIG_DEBUG_LOCK_ALLOC
>>   static struct lock_class_key nbd_key[3];
>>   static struct lock_class_key nbd_slock_key[3];
>> +static struct lock_class_key nbd_unix_iolock_key;
>>   static void nbd_reclassify_socket(struct socket *sock)
>>   {
>> @@ -1267,6 +1269,17 @@ static void nbd_reclassify_socket(struct socket *sock)
>>                             &nbd_slock_key[2],
>>                             "sk_lock-AF_UNIX-NBD",
>>                             &nbd_key[2]);
>> +        /*
>> +         * The AF_UNIX stream recvmsg/sendmsg paths serialize on
>> +         * u->iolock, not sk_lock, so it must be reclassified as
>> +         * well.  A held mutex cannot be reclassified; skip it in
>> +         * that case, as sock_allow_reclassification() does for
>> +         * sk_lock.
>> +         */
>> +        if (!mutex_is_locked(&unix_sk(sk)->iolock))
>> +            lockdep_set_class_and_name(&unix_sk(sk)->iolock,
>> +                           &nbd_unix_iolock_key,
>> +                           "&u->iolock-NBD");
>>           break;
>>       }
>>   }


Ping. I can respin with all the fixes (NBD_CMD_RECONFIGURE and correct from address) but
I at least want to get some feedback from the ndb maintainers if this is the right approach.

I definitely want to get rid of the lockdep false positive in our CI.