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Re: [Qemu-devel] [PATCH 07/29] 9pfs: local: introduce symlink-attack saf
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From: |
Jann Horn |
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Subject: |
Re: [Qemu-devel] [PATCH 07/29] 9pfs: local: introduce symlink-attack safe xattr helpers |
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Date: |
Thu, 23 Feb 2017 16:05:02 +0100 |
On Thu, Feb 23, 2017 at 4:02 PM, Eric Blake <address@hidden> wrote:
> On 02/20/2017 08:40 AM, Greg Kurz wrote:
>> All operations dealing with extended attributes are vulnerable to symlink
>> attacks because they use path-based syscalls which can traverse symbolic
>> links while walking through the dirname part of the path.
>>
>> The solution is to introduce helpers based on opendir_nofollow(). This
>> calls for "at" versions of the extended attribute syscalls, which don't
>> exist unfortunately. This patch implement them by simulating the "at"
>> behavior with fchdir(). Since the current working directory is process
>> wide, and we don't want to confuse another thread in QEMU, all the work
>> is done in a separate process.
>
> Can you emulate *at using /proc/fd/nnn/xyz?
I don't know much about QEMU internals, but QEMU supports running in a
chroot using the -chroot option, right? Does that already require procfs to be
mounted inside the chroot?