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From: Jens Axboe <axboe@kernel.dk>
To: Eric Biggers <ebiggers@kernel.org>
Cc: Ming Lei <ming.lei@redhat.com>,
	linux-aio@kvack.org, linux-block@vger.kernel.org,
	linux-api@vger.kernel.org, hch@lst.de, jmoyer@redhat.com,
	avi@scylladb.com, jannh@google.com, viro@zeniv.linux.org.uk
Subject: Re: [PATCH 11/19] block: implement bio helper to add iter bvec pages to bio
Date: Mon, 25 Feb 2019 21:34:36 -0700
Message-ID: <aa1184bb-b482-0637-21e4-1ddb0e7aea90@kernel.dk> (raw)
In-Reply-To: <20190226034613.GA676@sol.localdomain>

On 2/25/19 8:46 PM, Eric Biggers wrote:
> Hi Jens,
> 
> On Thu, Feb 21, 2019 at 10:45:27AM -0700, Jens Axboe wrote:
>> On 2/20/19 3:58 PM, Ming Lei wrote:
>>> On Mon, Feb 11, 2019 at 12:00:41PM -0700, Jens Axboe wrote:
>>>> For an ITER_BVEC, we can just iterate the iov and add the pages
>>>> to the bio directly. This requires that the caller doesn't releases
>>>> the pages on IO completion, we add a BIO_NO_PAGE_REF flag for that.
>>>>
>>>> The current two callers of bio_iov_iter_get_pages() are updated to
>>>> check if they need to release pages on completion. This makes them
>>>> work with bvecs that contain kernel mapped pages already.
>>>>
>>>> Reviewed-by: Hannes Reinecke <hare@suse.com>
>>>> Reviewed-by: Christoph Hellwig <hch@lst.de>
>>>> Signed-off-by: Jens Axboe <axboe@kernel.dk>
>>>> ---
>>>>  block/bio.c               | 59 ++++++++++++++++++++++++++++++++-------
>>>>  fs/block_dev.c            |  5 ++--
>>>>  fs/iomap.c                |  5 ++--
>>>>  include/linux/blk_types.h |  1 +
>>>>  4 files changed, 56 insertions(+), 14 deletions(-)
>>>>
>>>> diff --git a/block/bio.c b/block/bio.c
>>>> index 4db1008309ed..330df572cfb8 100644
>>>> --- a/block/bio.c
>>>> +++ b/block/bio.c
>>>> @@ -828,6 +828,23 @@ int bio_add_page(struct bio *bio, struct page *page,
>>>>  }
>>>>  EXPORT_SYMBOL(bio_add_page);
>>>>  
>>>> +static int __bio_iov_bvec_add_pages(struct bio *bio, struct iov_iter *iter)
>>>> +{
>>>> +	const struct bio_vec *bv = iter->bvec;
>>>> +	unsigned int len;
>>>> +	size_t size;
>>>> +
>>>> +	len = min_t(size_t, bv->bv_len, iter->count);
>>>> +	size = bio_add_page(bio, bv->bv_page, len,
>>>> +				bv->bv_offset + iter->iov_offset);
>>>
>>> iter->iov_offset needs to be subtracted from 'len', looks
>>> the following delta change[1] is required, otherwise memory corruption
>>> can be observed when running xfstests over loop/dio.
>>
>> Thanks, I folded this in.
>>
>> -- 
>> Jens Axboe
>>
> 
> syzkaller started hitting a crash on linux-next starting with this commit, and
> it still occurs even with your latest version that has Ming's fix folded in.
> Specifically, commit a566653ab5ab80a from your io_uring branch with commit date
> Sun Feb 24 08:20:53 2019 -0700.
> 
> Reproducer:
> 
> #define _GNU_SOURCE
> #include <fcntl.h>
> #include <linux/loop.h>
> #include <sys/ioctl.h>
> #include <sys/sendfile.h>
> #include <sys/syscall.h>
> #include <unistd.h>
> 
> int main(void)
> {
>         int memfd, loopfd;
> 
>         memfd = syscall(__NR_memfd_create, "foo", 0);
> 
>         pwrite(memfd, "\xa8", 1, 4096);
> 
>         loopfd = open("/dev/loop0", O_RDWR|O_DIRECT);
> 
>         ioctl(loopfd, LOOP_SET_FD, memfd);
> 
>         sendfile(loopfd, loopfd, NULL, 1000000);
> }
> 
> 
> Crash:
> 
> page:ffffea0001a6aab8 count:0 mapcount:0 mapping:0000000000000000 index:0x0
> flags: 0x100000000000000()
> raw: 0100000000000000 ffffea0001ad2c50 ffff88807fca49d0 0000000000000000
> raw: 0000000000000000 0000000000000000 00000000ffffffff
> page dumped because: VM_BUG_ON_PAGE(page_ref_count(page) == 0)

I see what this is, I'll cut a fix for this tomorrow.

-- 
Jens Axboe


  reply index

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-11 19:00 [PATCHSET v15] io_uring IO interface Jens Axboe
2019-02-11 19:00 ` [PATCH 01/19] fs: add an iopoll method to struct file_operations Jens Axboe
2019-02-11 19:00 ` [PATCH] io_uring: add io_uring_event cache hit information Jens Axboe
2019-02-11 19:00 ` [PATCH 02/19] block: wire up block device iopoll method Jens Axboe
2019-02-11 19:00 ` [PATCH 03/19] block: add bio_set_polled() helper Jens Axboe
2019-02-11 19:00 ` [PATCH 04/19] iomap: wire up the iopoll method Jens Axboe
2019-02-11 19:00 ` [PATCH 05/19] Add io_uring IO interface Jens Axboe
2019-02-11 19:00 ` [PATCH 06/19] io_uring: add fsync support Jens Axboe
2019-02-11 19:00 ` [PATCH 07/19] io_uring: support for IO polling Jens Axboe
2019-02-11 19:00 ` [PATCH 08/19] fs: add fget_many() and fput_many() Jens Axboe
2019-02-11 19:00 ` [PATCH 09/19] io_uring: use fget/fput_many() for file references Jens Axboe
2019-02-11 19:00 ` [PATCH 10/19] io_uring: batch io_kiocb allocation Jens Axboe
2019-02-11 19:00 ` [PATCH 11/19] block: implement bio helper to add iter bvec pages to bio Jens Axboe
2019-02-20 22:58   ` Ming Lei
2019-02-21 17:45     ` Jens Axboe
2019-02-26  3:46       ` Eric Biggers
2019-02-26  4:34         ` Jens Axboe [this message]
2019-02-26 15:54           ` Jens Axboe
2019-02-27  1:21             ` Ming Lei
2019-02-27  1:47               ` Jens Axboe
2019-02-27  1:53                 ` Ming Lei
2019-02-27  1:57                   ` Jens Axboe
2019-02-27  2:21                     ` Ming Lei
2019-02-27  2:28                       ` Jens Axboe
2019-02-27  2:37                         ` Ming Lei
2019-02-27  2:43                           ` Jens Axboe
2019-02-27  3:09                             ` Ming Lei
2019-02-27  3:37                               ` Jens Axboe
2019-02-27  3:43                                 ` Jens Axboe
2019-02-27  3:44                                 ` Ming Lei
2019-02-27  4:05                                   ` Jens Axboe
2019-02-27  4:06                                     ` Jens Axboe
2019-02-27 19:42                                       ` Christoph Hellwig
2019-02-28  8:37                                         ` Ming Lei
2019-02-27 23:35                         ` Ming Lei
2019-03-08  7:55                         ` Christoph Hellwig
2019-03-08  9:12                           ` Ming Lei
2019-03-08  8:18                     ` Christoph Hellwig
2019-02-11 19:00 ` [PATCH 12/19] io_uring: add support for pre-mapped user IO buffers Jens Axboe
2019-02-19 19:08   ` Jann Horn
2019-02-22 22:29     ` Jens Axboe
2019-02-11 19:00 ` [PATCH 13/19] net: split out functions related to registering inflight socket files Jens Axboe
2019-02-11 19:00 ` [PATCH 14/19] io_uring: add file set registration Jens Axboe
2019-02-19 16:12   ` Jann Horn
2019-02-22 22:29     ` Jens Axboe
2019-02-11 19:00 ` [PATCH 15/19] io_uring: add submission polling Jens Axboe
2019-02-11 19:00 ` [PATCH 16/19] io_uring: add io_kiocb ref count Jens Axboe
2019-02-11 19:00 ` [PATCH 17/19] io_uring: add support for IORING_OP_POLL Jens Axboe
2019-02-11 19:00 ` [PATCH 18/19] io_uring: allow workqueue item to handle multiple buffered requests Jens Axboe
2019-02-11 19:00 ` [PATCH 19/19] io_uring: add io_uring_event cache hit information Jens Axboe
2019-02-21 12:10 ` [PATCHSET v15] io_uring IO interface Marek Majkowski
2019-02-21 17:48   ` Jens Axboe
2019-02-22 15:01     ` Marek Majkowski
2019-02-22 22:32       ` Jens Axboe
  -- strict thread matches above, loose matches on Subject: below --
2019-02-09 21:13 [PATCHSET v14] " Jens Axboe
2019-02-09 21:13 ` [PATCH 11/19] block: implement bio helper to add iter bvec pages to bio Jens Axboe
2019-02-08 17:34 [PATCHSET v13] io_uring IO interface Jens Axboe
2019-02-08 17:34 ` [PATCH 11/19] block: implement bio helper to add iter bvec pages to bio Jens Axboe
2019-02-09  9:45   ` Hannes Reinecke

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