| Message ID | 1318882661-26859-1-git-send-email-dpmcgee@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
On Mon, Oct 17, 2011 at 4:51 PM, David Miller <davem@davemloft.net> wrote: > From: Dan McGee <dpmcgee@gmail.com> > Date: Mon, 17 Oct 2011 15:17:36 -0500 > >> Since commit 8a0a9bd4db63bc45e301, this comment in mmap_rnd() does not >> hold true as the value returned by get_random_int() will in fact be >> different every single call. Remove the comment and simplify the code >> back to its original desired form. >> >> This reverts commit a5adc91a4b44b5d1 which is no longer necessary. >> >> Signed-off-by: Dan McGee <dpmcgee@gmail.com> > > Can you please fix up all the other architectures which use the same > logic, because they have simply copied over what powerpc does? > > At a minimum, Sparc has two such locations. Aha, I wasn't aware this was also being done elsewhere as there was no comment to tip me off. I found the one in arch/sparc/kernel/sys_sparc_64.c (mmap_rnd) and have fixed that locally and will resend, but I'm not seeing get_random_int() in use anywhere else in that architecture so I'm not quite sure where your second mentioned location is- or did you just mean the two calls 2 lines apart in mmap_rnd()? I also did a quick glance over every other usage and didn't seen any other architectures doing anything funky, even in a slightly different way. -Dan
different every single call. Remove the comment and simplify the code back to its original desired form. This reverts commit a5adc91a4b44b5d1 which is no longer necessary. Signed-off-by: Dan McGee <dpmcgee@gmail.com> --- arch/powerpc/mm/mmap_64.c | 14 +++----------- 1 files changed, 3 insertions(+), 11 deletions(-) diff --git a/arch/powerpc/mm/mmap_64.c b/arch/powerpc/mm/mmap_64.c index 5a783d8..67a42ed 100644 --- a/arch/powerpc/mm/mmap_64.c +++ b/arch/powerpc/mm/mmap_64.c @@ -53,14 +53,6 @@ static inline int mmap_is_legacy(void) return sysctl_legacy_va_layout; } -/* - * Since get_random_int() returns the same value within a 1 jiffy window, - * we will almost always get the same randomisation for the stack and mmap - * region. This will mean the relative distance between stack and mmap will - * be the same. - * - * To avoid this we can shift the randomness by 1 bit. - */ static unsigned long mmap_rnd(void) { unsigned long rnd = 0; @@ -68,11 +60,11 @@ static unsigned long mmap_rnd(void) if (current->flags & PF_RANDOMIZE) { /* 8MB for 32bit, 1GB for 64bit */ if (is_32bit_task()) - rnd = (long)(get_random_int() % (1<<(22-PAGE_SHIFT))); + rnd = (long)(get_random_int() % (1<<(23-PAGE_SHIFT))); else - rnd = (long)(get_random_int() % (1<<(29-PAGE_SHIFT))); + rnd = (long)(get_random_int() % (1<<(30-PAGE_SHIFT))); } - return (rnd << PAGE_SHIFT) * 2; + return rnd << PAGE_SHIFT; } static inline unsigned long mmap_base(void)