Messages in this thread | | | From | Andy Lutomirski <> | Date | Mon, 3 Nov 2014 07:42:58 -0800 | Subject | Re: [PATCH 1/3] fs: add O_BENEATH flag to openat(2) |
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On Mon, Nov 3, 2014 at 7:20 AM, Al Viro <viro@zeniv.linux.org.uk> wrote: > On Mon, Nov 03, 2014 at 11:48:23AM +0000, David Drysdale wrote: >> Add a new O_BENEATH flag for openat(2) which restricts the >> provided path, rejecting (with -EACCES) paths that are not beneath >> the provided dfd. In particular, reject: >> - paths that contain .. components >> - paths that begin with / >> - symlinks that have paths as above. > > Yecch... The degree of usefulness aside (and I'm not convinced that it > is non-zero),
This is extremely useful in conjunction with seccomp.
> WTF pass one bit out of nameidata->flags in a separate argument? > Through the mutual recursion, no less... And then you are not even attempting > to detect symlinks that are not followed by interpretation of _any_ pathname.
How many symlinks like that are there? Is there anything except nd_jump_link users? All of those are in /proc. Arguably O_BENEATH should prevent traversal of all of those links.
--Andy
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