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Date: Thu, 19 Nov 2009 00:15:32 +0100 From: Oleg Nesterov <oleg@...hat.com> To: Jiri Slaby <jirislaby@...il.com> Cc: Ingo Molnar <mingo@...e.hu>, Neil Horman <nhorman@...driver.com>, Stephen Rothwell <sfr@...b.auug.org.au>, linux-kernel@...r.kernel.org, akpm@...ux-foundation.org, marcin.slusarz@...il.com, tglx@...utronix.de, mingo@...hat.com, hpa@...or.com, Linus Torvalds <torvalds@...ux-foundation.org> Subject: Re: [PATCH 0/3] extend get/setrlimit to support setting rlimits external to a process (v7) On 11/18, Jiri Slaby wrote: > > On the last point: I added explicit ACCESS_ONCE all over there. If you > don't like I will trash it. Just curious, why? I mean, do you have any example of the "bad" behaviour which is fixed by ACCESS_ONCE() ? > The only remaining weird user is in > kernel/acct.c: > /* > * Accounting records are not subject to resource limits. > */ > flim = current->signal->rlim[RLIMIT_FSIZE].rlim_cur; > current->signal->rlim[RLIMIT_FSIZE].rlim_cur = RLIM_INFINITY; > file->f_op->write(file, (char *)&ac, > sizeof(acct_t), &file->f_pos); > current->signal->rlim[RLIMIT_FSIZE].rlim_cur = flim; > > It means that threads of the process with PACCT caps have unlimited file > size for a short while. If there is setrlimit in between, it gets wiped > out as well. This is called when the whole thread-group exits, there are no live threads except current. We don't care if the new rlimit is lost afaics, but if RLIMIT_FSIZE is changed in between ->write() can fail. Not sure what can we do, perhaps just ignore this problem ;) At least, given that do_acct_process() does override_creds(), an ordinary user can't fool the accounting. 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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