Re: [RFC 2/2] fs,proc: Respect FMODE_WRITE when opening /proc/pid/fd/N

[David Herrmann]

Hi

On Tue, Apr 22, 2014 at 4:31 PM, Pavel Machek <pavel@xxxxxx> wrote:
> Such as here?
>
> http://www.securityfocus.com/archive/1/507386

Thanks, that's the first real example someone mentioned.

Quoted from your link:

> The reopen does check the inode permission, but it does not require
> you have any reachable path to the file. Someone _might_ use that as
> a traditional unix security mechanism, but if so it's probably quite rare.

In other words, the bug you describe is that /proc/pid/fd/ allows
access to objects without a reachable path to the only _real_
filesystem link. But isn't the same true for openat()?

Thanks
David
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