Date: Thu, 9 Sep 2010 14:31:18 +0900 (JST) From: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> To: Brad Spengler <spender@...ecurity.net> Cc: kosaki.motohiro@...fujitsu.com, Roland McGrath <roland@...hat.com>, Linus Torvalds <torvalds@...ux-foundation.org>, Andrew Morton <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org, oss-security@...ts.openwall.com, Solar Designer <solar@...nwall.com>, Kees Cook <kees.cook@...onical.com>, Al Viro <viro@...iv.linux.org.uk>, Oleg Nesterov <oleg@...hat.com>, Neil Horman <nhorman@...driver.com>, linux-fsdevel@...r.kernel.org, pageexec@...email.hu, "Brad Spengler <spender@...ecurity.net> Eugene Teo" <eugene@...hat.com> Subject: Re: [PATCH 1/3] setup_arg_pages: diagnose excessive argument size > I still don't think this addresses the whole problem. Without question, > the rlimit / 4 check is bogus. If nobody agrees with the intent of that > check, then it should be removed, but I think the better solution is to > fix the check so that it matches its original intent: let the initial > stack setup be up to 1/Xth of the min(rlimit, TASK_SIZE dependent upon > personality), which allows space for additional stack setup in the ELF > loader and then further growth once the process is live. If that > amount is overstepped, then the exec will return an error to the calling > process instead of being terminated. > > It might be useful to consult with the people who introduced/approved > the check in the first place, as they seemed to have reasons for > implementing it. Brad, sorry, I have bad news. glibc sysconf(_SC_ARG_MAX) is implemented by hard coded RLIMIT_STACK/4 heuristics. That said, at least _now_, we can't change this even though you disliked. That said, we can't break userland even though userland library is very crazy. I don't dislike your "1/Xth of the min(rlimit, TASK_SIZE dependent upon > personality)" idea. however I think You and Roland haven't agreed this point yet. he seems to want "unlimited" works as "unlimited". then, now I don't make such patch. Instead, I would propose to insert __vm_enough_memory() check in execve() pass. It prevent almost argv attack.
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