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Re: [Qemu-block] [PATCH v5] file-posix: specify expected filetypes
From: |
John Snow |
Subject: |
Re: [Qemu-block] [PATCH v5] file-posix: specify expected filetypes |
Date: |
Wed, 21 Mar 2018 16:26:06 -0400 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 |
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