Re: [PATCH] block: bio-integrity: fix potential null-ptr-deref in bio_integrity_free

[Ming Lei]

On Fri, Jun 07, 2024 at 09:32:29AM +0800, yebin wrote:
> 
> 
> On 2024/6/7 8:13, Ming Lei wrote:
> > On Thu, Jun 06, 2024 at 02:26:55PM +0800, Ye Bin wrote:
> > > From: Ye Bin <yebin10@xxxxxxxxxx>
> > > 
> > > There's a issue as follows when do format NVME with IO:
> > > BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
> > > PGD 101727f067 P4D 1011fae067 PUD fbed78067 PMD 0
> > > Oops: 0000 [#1] SMP NOPTI
> > > RIP: 0010:kfree+0x4f/0x160
> > > RSP: 0018:ff705a800912b910 EFLAGS: 00010247
> > > RAX: 0000000000000000 RBX: 0d06d30000000000 RCX: ff4fb320260ad990
> > > RDX: ff4fb30ee7acba40 RSI: 0000000000000000 RDI: 00b04cff80000000
> > > RBP: ff4fb30ee7acba40 R08: 0000000000000200 R09: ff705a800912bb60
> > > R10: 0000000000000000 R11: ff4fb3103b67c750 R12: ffffffff9a62d566
> > > R13: ff4fb30aa0530000 R14: 0000000000000000 R15: 000000000000000a
> > > FS:  00007f4399b6b700(0000) GS:ff4fb31040140000(0000) knlGS:0000000000000000
> > > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > CR2: 0000000000000008 CR3: 0000001014cd4002 CR4: 0000000000761ee0
> > > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > > DR3: 0000000000000000 DR6: 00000000fffe07f0 DR7: 0000000000000400
> > > PKRU: 55555554
> > > Call Trace:
> > >   bio_integrity_free+0xa6/0xb0
> > >   __bio_integrity_endio+0x8c/0xa0
> > >   bio_endio+0x2b/0x130
> > >   blk_update_request+0x78/0x2b0
> > >   blk_mq_end_request+0x1a/0x140
> > >   blk_mq_try_issue_directly+0x5d/0xc0
> > >   blk_mq_make_request+0x46b/0x540
> > >   generic_make_request+0x121/0x300
> > >   submit_bio+0x6c/0x140
> > >   __blkdev_direct_IO_simple+0x1ca/0x3a0
> > >   blkdev_direct_IO+0x3d9/0x460
> > >   generic_file_read_iter+0xb4/0xc60
> > >   new_sync_read+0x121/0x170
> > >   vfs_read+0x89/0x130
> > >   ksys_read+0x52/0xc0
> > >   do_syscall_64+0x5d/0x1d0
> > >   entry_SYSCALL_64_after_hwframe+0x65/0xca
> > > 
> > > Assuming a 512 byte directIO is issued, the initial logical block size of
> > > the state block device is 512 bytes, and then modified to 4096 bytes.
> > > Above issue may happen as follows:
> > >           Direct read                    format NVME
> > > __blkdev_direct_IO_simple(iocb, iter, nr_pages);
> > >    if ((pos | iov_iter_alignment(iter)) & (bdev_logical_block_size(bdev) - 1))
> > > 	-->The logical block size is 512, and the IO issued is 512 bytes,
> > > 	   which can be checked
> > >      return -EINVAL;
> > >    submit_bio(&bio);
> > >                                        nvme_dev_ioctl
> > >                                          case NVME_IOCTL_RESCAN:
> > >                                            nvme_queue_scan(ctrl);
> > >                                               ...
> > >                                              nvme_update_disk_info(disk, ns, id);
> > >                                                blk_queue_logical_block_size(disk->queue, bs);
> > >                                                  --> 512->4096
> > >       blk_queue_enter(q, flags)
> > >       blk_mq_make_request(q, bio)
> > >         bio_integrity_prep(bio)
> > > 	 len = bio_integrity_bytes(bi, bio_sectors(bio));
> > > 	   -->At this point, because the logical block size has increased to
> > > 	      4096 bytes, the calculated 'len' here is 0
> > >           buf = kmalloc(len, GFP_NOIO | q->bounce_gfp);
> > > 	   -->Passed in len=0 and returned buf=16
> > >           end = (((unsigned long) buf) + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
> > >           start = ((unsigned long) buf) >> PAGE_SHIFT;
> > >           nr_pages = end - start;  -->nr_pages == 1
> > >           bip->bip_flags |= BIP_BLOCK_INTEGRITY;
> > >           for (i = 0 ; i < nr_pages ; i++) {
> > >             if (len <= 0)
> > >                -->Not initializing the bip_vec of bio_integrity, will result
> > > 		 in null pointer access during subsequent releases. Even if
> > > 		 initialized, it will still cause subsequent releases access
> > > 		 null pointer because the buffer address is incorrect.
> > >               break;
> > > 
> > > Firstly, it is unreasonable to format NVME in the presence of IO. It is also
> > > possible to see IO smaller than the logical block size in the block layer for
> > > this type of concurrency. It is expected that this type of IO device will
> > > return an error, so exception handling should also be done for this type of
> > > IO to prevent null pointer access from causing system crashes.
> > Actually unaligned IO handling is one mess for nvme hardware. Yes, IO may fail,
> > but it is observed that meta buffer is overwrite by DMA in read IO.
> > 
> > Ye and Yi, can you test the following patch in your 'nvme format' & IO workload?
> > 
> > 
> > diff --git a/block/blk-core.c b/block/blk-core.c
> > index 82c3ae22d76d..a41ab4a3a398 100644
> > --- a/block/blk-core.c
> > +++ b/block/blk-core.c
> > @@ -336,6 +336,19 @@ int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags)
> >   	return 0;
> >   }
> > +static bool bio_unaligned(struct bio *bio)
> > +{
> > +	unsigned int bs = bdev_logical_block_size(bio->bi_bdev);
> > +
> > +	if (bio->bi_iter.bi_size & (bs - 1))
> > +	        return true;
> > +
> > +	if ((bio->bi_iter.bi_sector << SECTOR_SHIFT) & (bs - 1))
> > +	        return true;
> > +
> > +	return false;
> > +}
> I think this judgment is a bit incorrect. It should not be sufficient to
> only determine whether
> the length and starting sector are logically block aligned.

Can you explain why the two are not enough? Other limits should be handled
by bio split.


Thanks,
Ming