Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1238552

Re: [fuse-devel] [PATCH] fuse: break infinite loop in fuse_fill_write_pages()

Show all headers | View raw

On 10/02/2015 04:21 AM, Konstantin Khlebnikov wrote:
> Bump. Add more peopple in CC.
>
> On Mon, Sep 21, 2015 at 1:02 PM, Roman Gushchin <klamm@yandex-team.ru> wrote:
>> I got a report about unkillable task eating CPU. Thge further
>> investigation shows, that the problem is in the fuse_fill_write_pages()
>> function. If iov's first segment has zero length, we get an infinite
>> loop, because we never reach iov_iter_advance() call.

iov_iter_copy_from_user_atomic() eventually calls iterate_iovec(). The 
latter silently consumes zero-length iov. So I don't think "iov's first 
segment has zero length" can cause infinite loop.

Thanks,
Maxim

>>
>> Fix this by calling iov_iter_advance() before repeating an attempt to
>> copy data from userspace.
>>
>> A similar problem is described in 124d3b7041f ("fix writev regression:
>> pan hanging unkillable and un-straceable").
>>
>> Signed-off-by: Roman Gushchin <klamm@yandex-team.ru>
>> Cc: Miklos Szeredi <miklos@szeredi.hu>
>> ---
>>   fs/fuse/file.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
>> index f523f2f..195476a 100644
>> --- a/fs/fuse/file.c
>> +++ b/fs/fuse/file.c
>> @@ -1049,6 +1049,7 @@ static ssize_t fuse_fill_write_pages(struct fuse_req *req,
>>                  tmp = iov_iter_copy_from_user_atomic(page, ii, offset, bytes);
>>                  flush_dcache_page(page);
>>
>> +               iov_iter_advance(ii, tmp);
>>                  if (!tmp) {
>>                          unlock_page(page);
>>                          page_cache_release(page);
>> @@ -1061,7 +1062,6 @@ static ssize_t fuse_fill_write_pages(struct fuse_req *req,
>>                  req->page_descs[req->num_pages].length = tmp;
>>                  req->num_pages++;
>>
>> -               iov_iter_advance(ii, tmp);
>>                  count += tmp;
>>                  pos += tmp;
>>                  offset += tmp;
>> --
>> 2.4.3
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>> Please read the FAQ at  http://www.tux.org/lkml/
> ------------------------------------------------------------------------------
> _______________________________________________
> fuse-devel mailing list
> fuse-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/fuse-devel

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Re: [PATCH] fuse: break infinite loop in fuse_fill_write_pages() Konstantin Khlebnikov <koct9i@gmail.com> - 2015-10-02 13:30 +0200
  Re: [fuse-devel] [PATCH] fuse: break infinite loop in  fuse_fill_write_pages() Maxim Patlasov <mpatlasov@parallels.com> - 2015-10-02 21:30 +0200
    Re: [fuse-devel] [PATCH] fuse: break infinite loop in  fuse_fill_write_pages() Andrew Morton <akpm@linux-foundation.org> - 2015-10-03 00:10 +0200
      Re: [fuse-devel] [PATCH] fuse: break infinite loop in fuse_fill_write_pages() Konstantin Khlebnikov <koct9i@gmail.com> - 2015-10-03 04:00 +0200
        Re: [fuse-devel] [PATCH] fuse: break infinite loop in  fuse_fill_write_pages() Maxim Patlasov <mpatlasov@parallels.com> - 2015-10-05 20:40 +0200

csiph-web