Messages in this thread | | | From | Daniel Phillips <> | Subject | Re: [PATCH+discussion] symlink recursion | Date | Wed, 19 Jun 2002 16:44:48 +0200 |
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On Wednesday 19 June 2002 01:57, Linus Torvalds wrote: > I see no advantages to handling it by hand, since this isn't even a very > deep recursion, and since even if you do the recursive part by hand by a > linked list you still need to limit the depth _anyway_ to avoid DoS > attacks.
It's the recursive trip through the filesystem that causes the problem. Suddenly the stack space consumption becomes (N * greediest_filesystem) and that has to be factored into all worst case calculations. It's a huge hole to blow out of this severely restricted resource, so reducing N to 1 is a big deal.
Also, as a practical matter, it's much easier to lay down a rule for filesystem developers that reads: "thou shalt in no case use more than N bytes of stack on your longest path" than "in no case use more than N bytes of stack except on any symlink resolution path, in which case see the limit on recursive symlinks to know how to analyze that path".
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