Re: [Qemu-devel] [PATCH v5] file-posix: specify expected filetypes

[John Snow]

On 03/21/2018 04:25 PM, Kevin Wolf wrote:
> Am 21.03.2018 um 21:01 hat John Snow geschrieben:
>> Adjust each caller of raw_open_common to specify if they are expecting
>> host and character devices or not. Tighten expectations of file types upon
>> open in the common code and refuse types that are not expected.
>>
>> This has two effects:
>>
>> (1) Character and block devices are now considered deprecated for the
>>     'file' driver, which expects only S_IFREG, and
>> (2) no file-posix driver (file, host_cdrom, or host_device) can open
>>     directories now.
>>
>> I don't think there's a legitimate reason to open directories as if
>> they were files. This prevents QEMU from opening and attempting to probe
>> a directory inode, which can break in exciting ways. One of those ways
>> is lseek on ext4/xfs, which will return 0x7fffffffffffffff as the file
>> size instead of EISDIR. This can coax QEMU into responding with a
>> confusing "file too big" instead of "Hey, that's not a file".
>>
>> See: https://bugs.launchpad.net/qemu/+bug/1739304/
>> Signed-off-by: John Snow <address@hidden>
>> ---
>>
>> v5: rebase for 2.12.0-rc0
>>
>>  block/file-posix.c | 37 +++++++++++++++++++++++++++++--------
>>  qemu-doc.texi      |  6 ++++++
>>  2 files changed, 35 insertions(+), 8 deletions(-)
>>
>> diff --git a/block/file-posix.c b/block/file-posix.c
>> index d7fb772c14..31d9afe026 100644
>> --- a/block/file-posix.c
>> +++ b/block/file-posix.c
>> @@ -420,7 +420,8 @@ static QemuOptsList raw_runtime_opts = {
>>  };
>>  
>>  static int raw_open_common(BlockDriverState *bs, QDict *options,
>> -                           int bdrv_flags, int open_flags, Error **errp)
>> +                           int bdrv_flags, int open_flags,
>> +                           bool device, Error **errp)
>>  {
>>      BDRVRawState *s = bs->opaque;
>>      QemuOpts *opts;
>> @@ -558,10 +559,30 @@ static int raw_open_common(BlockDriverState *bs, QDict 
>> *options,
>>          error_setg_errno(errp, errno, "Could not stat file");
>>          goto fail;
>>      }
>> -    if (S_ISREG(st.st_mode)) {
>> -        s->discard_zeroes = true;
>> -        s->has_fallocate = true;
>> +
>> +    if (!device) {
>> +        if (S_ISBLK(st.st_mode)) {
>> +            warn_report("Opening a block device as file using 'file' "
>> +                        "driver is deprecated");
>> +        } else if (S_ISCHR(st.st_mode)) {
>> +            warn_report("Opening a character device as file using the 
>> 'file' "
>> +                        "driver is deprecated");
>> +        } else if (!S_ISREG(st.st_mode)) {
>> +            error_setg(errp, "A regular file was expected by the 'file' 
>> driver, "
>> +                       "but something else was given");
>> +            goto fail;
> 
> ret needs to be set here, otherwise we return success. In my test, I
> still got the wrong message: "Could not refresh total sector count:
> Invalid argument"
> 
>> +        } else {
>> +            s->discard_zeroes = true;
>> +            s->has_fallocate = true;
>> +        }
>> +    } else {
>> +        if (!(S_ISCHR(st.st_mode) || S_ISBLK(st.st_mode))) {
>> +            error_setg(errp, "host_device/host_cdrom driver expects either "
>> +                       "a character or block device");
>> +            goto fail;
> 
> Same here.
> 
>> +        }
>>      }
> 
> Do we want a qemu-iotests case for this?
> 
> Kevin
> 

I'll take the hint :)

--js