Messages in this thread |  | | Date | Fri, 5 Oct 2001 09:58:04 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: Security question: "Text file busy" overwriting executables but |
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On 5 Oct 2001, Eric W. Biederman wrote: > > The MAP_DENYWRITE rule was added a long time ago because people found actual > > workable DoS attacks > > Do you have any details. I would like to figure out what it takes to > export MAP_DENYWRITE safely to userspace.
I think it literally was /var/run/[uw]tmp, and using MAP_DENYWRITE to disable all logins.
But it pretty much covers _any_ logfiles that are readable (and thus openable) by users.
> Currently checking to see if the file is executable looks good > enough.
[ executable by the user in question, not just anybody ]
Yes, I suspect it is.
> The fix for bad permission (during a DOS attack) is either: > chmod correct_permissions foo > lsof foo | xargs kill
Well, if you cannot log in as root, it doesn't much matter what the "fix" is, so it's better to be safe than sorry.
Linus
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