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Re: [Qemu-block] [PATCH] file-posix: refuse to open directories
From: |
Kevin Wolf |
Subject: |
Re: [Qemu-block] [PATCH] file-posix: refuse to open directories |
Date: |
Fri, 22 Dec 2017 14:00:18 +0100 |
User-agent: |
Mutt/1.9.1 (2017-09-22) |
Am 21.12.2017 um 23:44 hat John Snow geschrieben:
> 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>
> ---
> block/file-posix.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/block/file-posix.c b/block/file-posix.c
> index 36ee89e940..bd29bdada6 100644
> --- a/block/file-posix.c
> +++ b/block/file-posix.c
> @@ -589,6 +589,11 @@ static int raw_open_common(BlockDriverState *bs, QDict
> *options,
> s->needs_alignment = true;
> }
> #endif
> + if (S_ISDIR(st.st_mode)) {
> + ret = -EISDIR;
> + error_setg_errno(errp, errno, "Cannot open directory as file");
> + goto fail;
> + }
I think instead of blacklisting directories, the callers should somehow
pass the file types they expect. Which would probably initially be
something like:
file:
S_IFREG: expected
S_IFBLK or S_IFCHR: deprecation warning
else: error
host_device / host_cdrom:
S_IFBLK or S_IFCHR: expected (which one depends on the OS)
else: error
Kevin