Re: [PATCH-next] nbd: fix incomplete validation of ioctl arg

[zhongjinghua]

ping...

Hello

Anyone looking this？

在 2023/3/14 15:10, zhongjinghua 写道:
> ping...
>
> Hello
>
> Anyone looking this？
>
> 在 2023/2/6 22:58, Zhong Jinghua 写道:
> > We tested and found an alarm caused by nbd_ioctl arg without 
> > verification.
> > The UBSAN warning calltrace like below:
> >
> > UBSAN: Undefined behaviour in fs/buffer.c:1709:35
> > signed integer overflow:
> > -9223372036854775808 - 1 cannot be represented in type 'long long int'
> > CPU: 3 PID: 2523 Comm: syz-executor.0 Not tainted 4.19.90 #1
> > Hardware name: linux,dummy-virt (DT)
> > Call trace:
> >   dump_backtrace+0x0/0x3f0 arch/arm64/kernel/time.c:78
> >   show_stack+0x28/0x38 arch/arm64/kernel/traps.c:158
> >   __dump_stack lib/dump_stack.c:77 [inline]
> >   dump_stack+0x170/0x1dc lib/dump_stack.c:118
> >   ubsan_epilogue+0x18/0xb4 lib/ubsan.c:161
> >   handle_overflow+0x188/0x1dc lib/ubsan.c:192
> >   __ubsan_handle_sub_overflow+0x34/0x44 lib/ubsan.c:206
> >   __block_write_full_page+0x94c/0xa20 fs/buffer.c:1709
> >   block_write_full_page+0x1f0/0x280 fs/buffer.c:2934
> >   blkdev_writepage+0x34/0x40 fs/block_dev.c:607
> >   __writepage+0x68/0xe8 mm/page-writeback.c:2305
> >   write_cache_pages+0x44c/0xc70 mm/page-writeback.c:2240
> >   generic_writepages+0xdc/0x148 mm/page-writeback.c:2329
> >   blkdev_writepages+0x2c/0x38 fs/block_dev.c:2114
> >   do_writepages+0xd4/0x250 mm/page-writeback.c:2344
> >
> > The reason for triggering this warning is __block_write_full_page()
> > -> i_size_read(inode) - 1 overflow.
> > inode->i_size is assigned in __nbd_ioctl() -> nbd_set_size() -> 
> > bytesize.
> > We think it is necessary to limit the size of arg to prevent errors.
> >
> > Moreover, __nbd_ioctl() -> nbd_add_socket(), arg will be cast to int.
> > Assuming the value of arg is 0x80000000000000001) (on a 64-bit machine),
> > it will become 1 after the coercion, which will return unexpected 
> > results.
> >
> > Fix it by adding checks to prevent passing in too large numbers.
> >
> > Signed-off-by: Zhong Jinghua <zhongjinghua@xxxxxxxxxx>
> > ---
> >   drivers/block/nbd.c | 6 ++++++
> >   1 file changed, 6 insertions(+)
> >
> > diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
> > index 592cfa8b765a..e1c954094b6c 100644
> > --- a/drivers/block/nbd.c
> > +++ b/drivers/block/nbd.c
> > @@ -325,6 +325,9 @@ static int nbd_set_size(struct nbd_device *nbd, 
> > loff_t bytesize,
> >       if (blk_validate_block_size(blksize))
> >           return -EINVAL;
> >   +    if (bytesize < 0)
> > +        return -EINVAL;
> > +
> >       nbd->config->bytesize = bytesize;
> >       nbd->config->blksize_bits = __ffs(blksize);
> >   @@ -1111,6 +1114,9 @@ static int nbd_add_socket(struct nbd_device 
> > *nbd, unsigned long arg,
> >       struct nbd_sock *nsock;
> >       int err;
> >   +    /* Arg will be cast to int, check it to avoid overflow */
> > +    if (arg > INT_MAX)
> > +        return -EINVAL;
> >       sock = nbd_get_socket(nbd, arg, &err);
> >       if (!sock)
> >           return err;