Re: [PATCH] block: reexpand iov_iter after read/write

[Pavel Begunkov <asml.silence@gmail.com>]

On 06/04/2021 02:28, yangerkun wrote:
> Ping...

It wasn't forgotten, but wouln't have worked because of
other reasons. With these two already queued, that's a
different story.

https://git.kernel.dk/cgit/linux-block/commit/?h=io_uring-5.12&id=07204f21577a1d882f0259590c3553fe6a476381
https://git.kernel.dk/cgit/linux-block/commit/?h=io_uring-5.12&id=230d50d448acb6639991440913299e50cacf1daf

Can you re-confirm, that the bug is still there (should be)
and your patch fixes it?

> 
> 在 2021/4/1 15:18, yangerkun 写道:
>> We get a bug:
>>
>> BUG: KASAN: slab-out-of-bounds in iov_iter_revert+0x11c/0x404
>> lib/iov_iter.c:1139
>> Read of size 8 at addr ffff0000d3fb11f8 by task
>>
>> CPU: 0 PID: 12582 Comm: syz-executor.2 Not tainted
>> 5.10.0-00843-g352c8610ccd2 #2
>> Hardware name: linux,dummy-virt (DT)
>> Call trace:
>>   dump_backtrace+0x0/0x2d0 arch/arm64/kernel/stacktrace.c:132
>>   show_stack+0x28/0x34 arch/arm64/kernel/stacktrace.c:196
>>   __dump_stack lib/dump_stack.c:77 [inline]
>>   dump_stack+0x110/0x164 lib/dump_stack.c:118
>>   print_address_description+0x78/0x5c8 mm/kasan/report.c:385
>>   __kasan_report mm/kasan/report.c:545 [inline]
>>   kasan_report+0x148/0x1e4 mm/kasan/report.c:562
>>   check_memory_region_inline mm/kasan/generic.c:183 [inline]
>>   __asan_load8+0xb4/0xbc mm/kasan/generic.c:252
>>   iov_iter_revert+0x11c/0x404 lib/iov_iter.c:1139
>>   io_read fs/io_uring.c:3421 [inline]
>>   io_issue_sqe+0x2344/0x2d64 fs/io_uring.c:5943
>>   __io_queue_sqe+0x19c/0x520 fs/io_uring.c:6260
>>   io_queue_sqe+0x2a4/0x590 fs/io_uring.c:6326
>>   io_submit_sqe fs/io_uring.c:6395 [inline]
>>   io_submit_sqes+0x4c0/0xa04 fs/io_uring.c:6624
>>   __do_sys_io_uring_enter fs/io_uring.c:9013 [inline]
>>   __se_sys_io_uring_enter fs/io_uring.c:8960 [inline]
>>   __arm64_sys_io_uring_enter+0x190/0x708 fs/io_uring.c:8960
>>   __invoke_syscall arch/arm64/kernel/syscall.c:36 [inline]
>>   invoke_syscall arch/arm64/kernel/syscall.c:48 [inline]
>>   el0_svc_common arch/arm64/kernel/syscall.c:158 [inline]
>>   do_el0_svc+0x120/0x290 arch/arm64/kernel/syscall.c:227
>>   el0_svc+0x1c/0x28 arch/arm64/kernel/entry-common.c:367
>>   el0_sync_handler+0x98/0x170 arch/arm64/kernel/entry-common.c:383
>>   el0_sync+0x140/0x180 arch/arm64/kernel/entry.S:670
>>
>> Allocated by task 12570:
>>   stack_trace_save+0x80/0xb8 kernel/stacktrace.c:121
>>   kasan_save_stack mm/kasan/common.c:48 [inline]
>>   kasan_set_track mm/kasan/common.c:56 [inline]
>>   __kasan_kmalloc+0xdc/0x120 mm/kasan/common.c:461
>>   kasan_kmalloc+0xc/0x14 mm/kasan/common.c:475
>>   __kmalloc+0x23c/0x334 mm/slub.c:3970
>>   kmalloc include/linux/slab.h:557 [inline]
>>   __io_alloc_async_data+0x68/0x9c fs/io_uring.c:3210
>>   io_setup_async_rw fs/io_uring.c:3229 [inline]
>>   io_read fs/io_uring.c:3436 [inline]
>>   io_issue_sqe+0x2954/0x2d64 fs/io_uring.c:5943
>>   __io_queue_sqe+0x19c/0x520 fs/io_uring.c:6260
>>   io_queue_sqe+0x2a4/0x590 fs/io_uring.c:6326
>>   io_submit_sqe fs/io_uring.c:6395 [inline]
>>   io_submit_sqes+0x4c0/0xa04 fs/io_uring.c:6624
>>   __do_sys_io_uring_enter fs/io_uring.c:9013 [inline]
>>   __se_sys_io_uring_enter fs/io_uring.c:8960 [inline]
>>   __arm64_sys_io_uring_enter+0x190/0x708 fs/io_uring.c:8960
>>   __invoke_syscall arch/arm64/kernel/syscall.c:36 [inline]
>>   invoke_syscall arch/arm64/kernel/syscall.c:48 [inline]
>>   el0_svc_common arch/arm64/kernel/syscall.c:158 [inline]
>>   do_el0_svc+0x120/0x290 arch/arm64/kernel/syscall.c:227
>>   el0_svc+0x1c/0x28 arch/arm64/kernel/entry-common.c:367
>>   el0_sync_handler+0x98/0x170 arch/arm64/kernel/entry-common.c:383
>>   el0_sync+0x140/0x180 arch/arm64/kernel/entry.S:670
>>
>> Freed by task 12570:
>>   stack_trace_save+0x80/0xb8 kernel/stacktrace.c:121
>>   kasan_save_stack mm/kasan/common.c:48 [inline]
>>   kasan_set_track+0x38/0x6c mm/kasan/common.c:56
>>   kasan_set_free_info+0x20/0x40 mm/kasan/generic.c:355
>>   __kasan_slab_free+0x124/0x150 mm/kasan/common.c:422
>>   kasan_slab_free+0x10/0x1c mm/kasan/common.c:431
>>   slab_free_hook mm/slub.c:1544 [inline]
>>   slab_free_freelist_hook mm/slub.c:1577 [inline]
>>   slab_free mm/slub.c:3142 [inline]
>>   kfree+0x104/0x38c mm/slub.c:4124
>>   io_dismantle_req fs/io_uring.c:1855 [inline]
>>   __io_free_req+0x70/0x254 fs/io_uring.c:1867
>>   io_put_req_find_next fs/io_uring.c:2173 [inline]
>>   __io_queue_sqe+0x1fc/0x520 fs/io_uring.c:6279
>>   __io_req_task_submit+0x154/0x21c fs/io_uring.c:2051
>>   io_req_task_submit+0x2c/0x44 fs/io_uring.c:2063
>>   task_work_run+0xdc/0x128 kernel/task_work.c:151
>>   get_signal+0x6f8/0x980 kernel/signal.c:2562
>>   do_signal+0x108/0x3a4 arch/arm64/kernel/signal.c:658
>>   do_notify_resume+0xbc/0x25c arch/arm64/kernel/signal.c:722
>>   work_pending+0xc/0x180
>>
>> blkdev_read_iter can truncate iov_iter's count since the count + pos may
>> exceed the size of the blkdev. This will confuse io_read that we have
>> consume the iovec. And once we do the iov_iter_revert in io_read, we
>> will trigger the slab-out-of-bounds. Fix it by reexpand the count with
>> size has been truncated.
>>
>> blkdev_write_iter can trigger the problem too.
>>
>> Signed-off-by: yangerkun <yangerkun@huawei.com>
>> ---
>>   fs/block_dev.c | 20 +++++++++++++++++---
>>   1 file changed, 17 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/block_dev.c b/fs/block_dev.c
>> index 92ed7d5df677..788e1014576f 100644
>> --- a/fs/block_dev.c
>> +++ b/fs/block_dev.c
>> @@ -1680,6 +1680,7 @@ ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
>>       struct inode *bd_inode = bdev_file_inode(file);
>>       loff_t size = i_size_read(bd_inode);
>>       struct blk_plug plug;
>> +    size_t shorted = 0;
>>       ssize_t ret;
>>         if (bdev_read_only(I_BDEV(bd_inode)))
>> @@ -1697,12 +1698,17 @@ ssize_t blkdev_write_iter(struct kiocb *iocb, struct iov_iter *from)
>>       if ((iocb->ki_flags & (IOCB_NOWAIT | IOCB_DIRECT)) == IOCB_NOWAIT)
>>           return -EOPNOTSUPP;
>>   -    iov_iter_truncate(from, size - iocb->ki_pos);
>> +    size -= iocb->ki_pos;
>> +    if (iov_iter_count(from) > size) {
>> +        shorted = iov_iter_count(from) - size;
>> +        iov_iter_truncate(from, size);
>> +    }
>>         blk_start_plug(&plug);
>>       ret = __generic_file_write_iter(iocb, from);
>>       if (ret > 0)
>>           ret = generic_write_sync(iocb, ret);
>> +    iov_iter_reexpand(from, iov_iter_count(from) + shorted);
>>       blk_finish_plug(&plug);
>>       return ret;
>>   }
>> @@ -1714,13 +1720,21 @@ ssize_t blkdev_read_iter(struct kiocb *iocb, struct iov_iter *to)
>>       struct inode *bd_inode = bdev_file_inode(file);
>>       loff_t size = i_size_read(bd_inode);
>>       loff_t pos = iocb->ki_pos;
>> +    size_t shorted = 0;
>> +    ssize_t ret;
>>         if (pos >= size)
>>           return 0;
>>         size -= pos;
>> -    iov_iter_truncate(to, size);
>> -    return generic_file_read_iter(iocb, to);
>> +    if (iov_iter_count(to) > size) {
>> +        shorted = iov_iter_count(to) - size;
>> +        iov_iter_truncate(to, size);
>> +    }
>> +
>> +    ret = generic_file_read_iter(iocb, to);
>> +    iov_iter_reexpand(to, iov_iter_count(to) + shorted);
>> +    return ret;
>>   }
>>   EXPORT_SYMBOL_GPL(blkdev_read_iter);
>>  

-- 
Pavel Begunkov