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Date: Mon, 30 Mar 2009 03:40:40 +0200 From: Oleg Nesterov <oleg@...hat.com> To: Al Viro <viro@...IV.linux.org.uk> Cc: Hugh Dickins <hugh@...itas.com>, Linus Torvalds <torvalds@...ux-foundation.org>, Andrew Morton <akpm@...ux-foundation.org>, Joe Malicki <jmalicki@...acarta.com>, Michael Itz <mitz@...acarta.com>, Kenneth Baker <bakerk@...acarta.com>, Chris Wright <chrisw@...s-sol.org>, David Howells <dhowells@...hat.com>, Alexey Dobriyan <adobriyan@...il.com>, Greg Kroah-Hartman <gregkh@...e.de>, linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: Q: check_unsafe_exec() races (Was: [PATCH 2/4] fix setuid sometimes doesn't) On 03/30, Oleg Nesterov wrote: > > On 03/30, Al Viro wrote: > > > > On Mon, Mar 30, 2009 at 02:08:43AM +0100, Al Viro wrote: > > > > > So... > > > * check_unsafe_exec() locks current->fs shared, goes through all > > > threads comparing their ->fs with our, if the number doesn't match - bail > > > out. Otherwise we mark it "under exec". > > Unless I missed something again, check_unsafe_exec() should check "under exec" > after it takes fs->lock. If set - we are racing with sub-thread, return -EAGAIN. > > We can't proceed. If that another exec() fails, it will clear "under exec" at > the end of do_execve(), before we kill other threads. Or we need a counter to mark/unmark. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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