Date: Tue, 26 Jul 2016 15:55:28 +0000 From: Jason Cooper <jason@...edaemon.net> To: Kees Cook <keescook@...omium.org> Cc: "Roberts, William C" <william.c.roberts@...el.com>, linux-mm@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, Russell King - ARM Linux <linux@....linux.org.uk>, Andrew Morton <akpm@...ux-foundation.org>, Theodore Ts'o <tytso@....edu>, Arnd Bergmann <arnd@...db.de>, Greg KH <gregkh@...uxfoundation.org>, Catalin Marinas <catalin.marinas@....com>, Will Deacon <will.deacon@....com>, Ralf Baechle <ralf@...ux-mips.org>, "benh@...nel.crashing.org" <benh@...nel.crashing.org>, Paul Mackerras <paulus@...ba.org>, Michael Ellerman <mpe@...erman.id.au>, "David S. Miller" <davem@...emloft.net>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>, Al Viro <viro@...iv.linux.org.uk>, Nick Kralevich <nnk@...gle.com>, Jeffrey Vander Stoep <jeffv@...gle.com>, Mark Salyzyn <salyzyn@...roid.com>, Daniel Cashman <dcashman@...roid.com> Subject: Re: [RFC patch 1/6] random: Simplify API for random address requests On Mon, Jul 25, 2016 at 09:44:27PM -0700, Kees Cook wrote: > On Mon, Jul 25, 2016 at 8:01 PM, Jason Cooper <jason@...edaemon.net> wrote: > > To date, all callers of randomize_range() have set the length to 0, and > > check for a zero return value. For the current callers, the only way > > to get zero returned is if end <= start. Since they are all adding a > > constant to the start address, this is unnecessary. > > > > We can remove a bunch of needless checks by simplifying the API to do > > just what everyone wants, return an address between [start, start + > > range]. > > > > While we're here, s/get_random_int/get_random_long/. No current call > > site is adversely affected by get_random_int(), since all current range > > requests are < MAX_UINT. However, we should match caller expectations > > to avoid coming up short (ha!) in the future. > > > > Signed-off-by: Jason Cooper <jason@...edaemon.net> > > --- > > drivers/char/random.c | 17 ++++------------- > > include/linux/random.h | 2 +- > > 2 files changed, 5 insertions(+), 14 deletions(-) > > > > diff --git a/drivers/char/random.c b/drivers/char/random.c > > index 0158d3bff7e5..1251cb2cbab2 100644 > > --- a/drivers/char/random.c > > +++ b/drivers/char/random.c > > @@ -1822,22 +1822,13 @@ unsigned long get_random_long(void) > > EXPORT_SYMBOL(get_random_long); > > > > /* > > - * randomize_range() returns a start address such that > > - * > > - * [...... <range> .....] > > - * start end > > - * > > - * a <range> with size "len" starting at the return value is inside in the > > - * area defined by [start, end], but is otherwise randomized. > > + * randomize_addr() returns a page aligned address within [start, start + > > + * range] > > */ > > unsigned long > > -randomize_range(unsigned long start, unsigned long end, unsigned long len) > > +randomize_addr(unsigned long start, unsigned long range) > > Also, this series isn't bisectable since randomize_range gets removed > here before the callers are updated. Perhaps add a macro that calls > randomize_addr with a BUG_ON for len != 0? (And then remove it in the > last patch?) No, I was thinking just add randomize_addr() in the first patch, convert all the callers, then the last patch would remove randomize_range(). That way the last patch can be a cleanup in a later merge window if needed. thx, Jason.
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