From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> To: Bhupesh Sharma <bhsharma@redhat.com>, linuxppc-dev@lists.ozlabs.org, kernel-hardening@lists.openwall.com, linux-kernel@vger.kernel.org Cc: alistair@popple.id.au, agust@denx.de, keescook@chromium.org, bhsharma@redhat.com, dcashman@android.com, oss@buserror.net, paulus@samba.org, dcashman@google.com, bhupesh.linux@gmail.com, agraf@suse.com Subject: Re: [PATCH v3] powerpc: mm: support ARCH_MMAP_RND_BITS Date: Thu, 13 Apr 2017 12:06:27 +0530 [thread overview] Message-ID: <87shlcq0es.fsf@skywalker.in.ibm.com> (raw) In-Reply-To: <1490730347-5165-1-git-send-email-bhsharma@redhat.com> Bhupesh Sharma <bhsharma@redhat.com> writes: > powerpc arch_mmap_rnd() currently uses hard-coded values - (23-PAGE_SHIFT) for > 32-bit and (30-PAGE_SHIFT) for 64-bit, to generate the random offset > for the mmap base address for a ASLR ELF. > > This patch makes sure that powerpc mmap arch_mmap_rnd() implementation > is similar to other ARCHs (like x86, arm64) and uses mmap_rnd_bits > and helpers to generate the mmap address randomization. > > The maximum and minimum randomization range values represent > a compromise between increased ASLR effectiveness and avoiding > address-space fragmentation. > > Using the Kconfig option and suitable /proc tunable, platform > developers may choose where to place this compromise. > > Also this patch keeps the default values as new minimums. > > Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com> > Reviewed-by: Kees Cook <keescook@chromium.org> > --- > * Changes since v2: > v2 can be seen here (https://patchwork.kernel.org/patch/9551509/) > - Changed a few minimum and maximum randomization ranges as per Michael's suggestion. > - Corrected Kees's email address in the Reviewed-by line. > - Added further comments in kconfig to explain how the address ranges were worked out. > > * Changes since v1: > v1 can be seen here (https://lists.ozlabs.org/pipermail/linuxppc-dev/2017-February/153594.html) > - No functional change in this patch. > - Dropped PATCH 2/2 from v1 as recommended by Kees Cook. > > arch/powerpc/Kconfig | 44 ++++++++++++++++++++++++++++++++++++++++++++ > arch/powerpc/mm/mmap.c | 7 ++++--- > 2 files changed, 48 insertions(+), 3 deletions(-) > > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig > index 97a8bc8..84aae67 100644 > --- a/arch/powerpc/Kconfig > +++ b/arch/powerpc/Kconfig > @@ -22,6 +22,48 @@ config MMU > bool > default y > > +# min bits determined by the following formula: > +# VA_BITS - PAGE_SHIFT - CONSTANT > +# where, > +# VA_BITS = 46 bits for 64BIT and 4GB - 1 Page = 31 bits for 32BIT Where did we derive that 46 bits from ? is that based on TASK_SIZE ? > +# CONSTANT = 16 for 64BIT and 8 for 32BIT > +config ARCH_MMAP_RND_BITS_MIN > + default 5 if PPC_256K_PAGES && 32BIT # 31 - 18 - 8 = 5 > + default 7 if PPC_64K_PAGES && 32BIT # 31 - 16 - 8 = 7 > + default 9 if PPC_16K_PAGES && 32BIT # 31 - 14 - 8 = 9 > + default 11 if PPC_4K_PAGES && 32BIT # 31 - 12 - 8 = 11 > + default 12 if PPC_256K_PAGES && 64BIT # 46 - 18 - 16 = 12 > + default 14 if PPC_64K_PAGES && 64BIT # 46 - 16 - 16 = 14 > + default 16 if PPC_16K_PAGES && 64BIT # 46 - 14 - 16 = 16 > + default 18 if PPC_4K_PAGES && 64BIT # 46 - 12 - 16 = 18 > + > +# max bits determined by the following formula: -aneesh
WARNING: multiple messages have this Message-ID (diff)
From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> To: Bhupesh Sharma <bhsharma@redhat.com>, linuxppc-dev@lists.ozlabs.org, kernel-hardening@lists.openwall.com, linux-kernel@vger.kernel.org Cc: alistair@popple.id.au, agust@denx.de, keescook@chromium.org, dcashman@android.com, oss@buserror.net, paulus@samba.org, dcashman@google.com, bhupesh.linux@gmail.com, agraf@suse.com Subject: [kernel-hardening] Re: [PATCH v3] powerpc: mm: support ARCH_MMAP_RND_BITS Date: Thu, 13 Apr 2017 12:06:27 +0530 [thread overview] Message-ID: <87shlcq0es.fsf@skywalker.in.ibm.com> (raw) In-Reply-To: <1490730347-5165-1-git-send-email-bhsharma@redhat.com> Bhupesh Sharma <bhsharma@redhat.com> writes: > powerpc arch_mmap_rnd() currently uses hard-coded values - (23-PAGE_SHIFT) for > 32-bit and (30-PAGE_SHIFT) for 64-bit, to generate the random offset > for the mmap base address for a ASLR ELF. > > This patch makes sure that powerpc mmap arch_mmap_rnd() implementation > is similar to other ARCHs (like x86, arm64) and uses mmap_rnd_bits > and helpers to generate the mmap address randomization. > > The maximum and minimum randomization range values represent > a compromise between increased ASLR effectiveness and avoiding > address-space fragmentation. > > Using the Kconfig option and suitable /proc tunable, platform > developers may choose where to place this compromise. > > Also this patch keeps the default values as new minimums. > > Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com> > Reviewed-by: Kees Cook <keescook@chromium.org> > --- > * Changes since v2: > v2 can be seen here (https://patchwork.kernel.org/patch/9551509/) > - Changed a few minimum and maximum randomization ranges as per Michael's suggestion. > - Corrected Kees's email address in the Reviewed-by line. > - Added further comments in kconfig to explain how the address ranges were worked out. > > * Changes since v1: > v1 can be seen here (https://lists.ozlabs.org/pipermail/linuxppc-dev/2017-February/153594.html) > - No functional change in this patch. > - Dropped PATCH 2/2 from v1 as recommended by Kees Cook. > > arch/powerpc/Kconfig | 44 ++++++++++++++++++++++++++++++++++++++++++++ > arch/powerpc/mm/mmap.c | 7 ++++--- > 2 files changed, 48 insertions(+), 3 deletions(-) > > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig > index 97a8bc8..84aae67 100644 > --- a/arch/powerpc/Kconfig > +++ b/arch/powerpc/Kconfig > @@ -22,6 +22,48 @@ config MMU > bool > default y > > +# min bits determined by the following formula: > +# VA_BITS - PAGE_SHIFT - CONSTANT > +# where, > +# VA_BITS = 46 bits for 64BIT and 4GB - 1 Page = 31 bits for 32BIT Where did we derive that 46 bits from ? is that based on TASK_SIZE ? > +# CONSTANT = 16 for 64BIT and 8 for 32BIT > +config ARCH_MMAP_RND_BITS_MIN > + default 5 if PPC_256K_PAGES && 32BIT # 31 - 18 - 8 = 5 > + default 7 if PPC_64K_PAGES && 32BIT # 31 - 16 - 8 = 7 > + default 9 if PPC_16K_PAGES && 32BIT # 31 - 14 - 8 = 9 > + default 11 if PPC_4K_PAGES && 32BIT # 31 - 12 - 8 = 11 > + default 12 if PPC_256K_PAGES && 64BIT # 46 - 18 - 16 = 12 > + default 14 if PPC_64K_PAGES && 64BIT # 46 - 16 - 16 = 14 > + default 16 if PPC_16K_PAGES && 64BIT # 46 - 14 - 16 = 16 > + default 18 if PPC_4K_PAGES && 64BIT # 46 - 12 - 16 = 18 > + > +# max bits determined by the following formula: -aneesh
next prev parent reply other threads:[~2017-04-13 6:36 UTC|newest] Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-03-28 19:45 [PATCH v3] powerpc: mm: support ARCH_MMAP_RND_BITS Bhupesh Sharma 2017-03-28 19:45 ` [kernel-hardening] " Bhupesh Sharma 2017-04-10 17:20 ` Bhupesh Sharma 2017-04-10 17:20 ` [kernel-hardening] " Bhupesh Sharma 2017-04-13 6:36 ` Aneesh Kumar K.V [this message] 2017-04-13 6:36 ` Aneesh Kumar K.V 2017-04-13 6:52 ` Bhupesh Sharma 2017-04-13 6:52 ` [kernel-hardening] " Bhupesh Sharma 2017-04-13 6:58 ` Aneesh Kumar K.V 2017-04-13 6:58 ` [kernel-hardening] " Aneesh Kumar K.V 2017-04-13 7:09 ` Balbir Singh 2017-04-13 7:09 ` [kernel-hardening] " Balbir Singh 2017-04-13 7:09 ` Balbir Singh 2017-04-17 4:48 ` Bhupesh SHARMA 2017-04-17 4:48 ` [kernel-hardening] " Bhupesh SHARMA 2017-04-17 4:48 ` Bhupesh SHARMA 2017-04-13 7:46 ` Bhupesh Sharma 2017-04-13 7:46 ` [kernel-hardening] " Bhupesh Sharma
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