| Message ID | 1492698980-19510-1-git-send-email-mpe@ellerman.id.au (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Apr 20, 2017 at 7:36 AM, Michael Ellerman <mpe@ellerman.id.au> wrote: > Add powerpc support for mmap_rnd_bits and mmap_rnd_compat_bits, which are two > sysctls that allow a user to configure the number of bits of randomness used for > ASLR. > > Because of the way the Kconfig for ARCH_MMAP_RND_BITS is defined, we have to > construct at least the MIN value in Kconfig, vs in a header which would be more > natural. Given that we just go ahead and do it all in Kconfig. > > At least according to the code (the documentation makes no mention of it), the > value is defined as the number of bits of randomisation *of the page*, not the > address. This makes some sense, with larger page sizes more of the low bits are > forced to zero, which would reduce the randomisation if we didn't take the > PAGE_SIZE into account. However it does mean the min/max values have to change > depending on the PAGE_SIZE in order to actually limit the amount of address > space consumed by the randomisation. > > The result of that is that we have to define the default values based on both > 32-bit vs 64-bit, but also the configured PAGE_SIZE. Furthermore now that we > have 128TB address space support on Book3S, we also have to take that into > account. > > Finally we can wire up the value in arch_mmap_rnd(). > > Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> > Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com> > --- > arch/powerpc/Kconfig | 44 ++++++++++++++++++++++++++++++++++++++++++++ > arch/powerpc/mm/mmap.c | 11 ++++++----- > 2 files changed, 50 insertions(+), 5 deletions(-) > > v2: Fix the 32-bit MAX value incorrectly using MIN as spotted by Kees. > > Kees/Bhupesh, would love a Review/Ack/Tested-by from you, I'll plan to merge > this later today (Friday) my time. Reviewed-by: Kees Cook <keescook@chromium.org> Looks good! -Kees > > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig > index 97a8bc8a095c..6f0503951e94 100644 > --- a/arch/powerpc/Kconfig > +++ b/arch/powerpc/Kconfig > @@ -22,6 +22,48 @@ config MMU > bool > default y > > +config ARCH_MMAP_RND_BITS_MAX > + # On Book3S 64, the default virtual address space for 64-bit processes > + # is 2^47 (128TB). As a maximum, allow randomisation to consume up to > + # 32T of address space (2^45), which should ensure a reasonable gap > + # between bottom-up and top-down allocations for applications that > + # consume "normal" amounts of address space. Book3S 64 only supports 64K > + # and 4K page sizes. > + default 29 if PPC_BOOK3S_64 && PPC_64K_PAGES # 29 = 45 (32T) - 16 (64K) > + default 33 if PPC_BOOK3S_64 # 33 = 45 (32T) - 12 (4K) > + # > + # On all other 64-bit platforms (currently only Book3E), the virtual > + # address space is 2^46 (64TB). Allow randomisation to consume up to 16T > + # of address space (2^44). Only 4K page sizes are supported. > + default 32 if 64BIT # 32 = 44 (16T) - 12 (4K) > + # > + # For 32-bit, use the compat values, as they're the same. > + default ARCH_MMAP_RND_COMPAT_BITS_MAX > + > +config ARCH_MMAP_RND_BITS_MIN > + # Allow randomisation to consume up to 1GB of address space (2^30). > + default 14 if 64BIT && PPC_64K_PAGES # 14 = 30 (1GB) - 16 (64K) > + default 18 if 64BIT # 18 = 30 (1GB) - 12 (4K) > + # > + # For 32-bit, use the compat values, as they're the same. > + default ARCH_MMAP_RND_COMPAT_BITS_MIN > + > +config ARCH_MMAP_RND_COMPAT_BITS_MAX > + # Total virtual address space for 32-bit processes is 2^31 (2GB). > + # Allow randomisation to consume up to 512MB of address space (2^29). > + default 11 if PPC_256K_PAGES # 11 = 29 (512MB) - 18 (256K) > + default 13 if PPC_64K_PAGES # 13 = 29 (512MB) - 16 (64K) > + default 15 if PPC_16K_PAGES # 15 = 29 (512MB) - 14 (16K) > + default 17 # 17 = 29 (512MB) - 12 (4K) > + > +config ARCH_MMAP_RND_COMPAT_BITS_MIN > + # Total virtual address space for 32-bit processes is 2^31 (2GB). > + # Allow randomisation to consume up to 8MB of address space (2^23). > + default 5 if PPC_256K_PAGES # 5 = 23 (8MB) - 18 (256K) > + default 7 if PPC_64K_PAGES # 7 = 23 (8MB) - 16 (64K) > + default 9 if PPC_16K_PAGES # 9 = 23 (8MB) - 14 (16K) > + default 11 # 11 = 23 (8MB) - 12 (4K) > + > config HAVE_SETUP_PER_CPU_AREA > def_bool PPC64 > > @@ -120,6 +162,8 @@ config PPC > select HAVE_ARCH_HARDENED_USERCOPY > select HAVE_ARCH_JUMP_LABEL > select HAVE_ARCH_KGDB > + select HAVE_ARCH_MMAP_RND_BITS > + select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT > select HAVE_ARCH_SECCOMP_FILTER > select HAVE_ARCH_TRACEHOOK > select HAVE_CBPF_JIT if !PPC64 > diff --git a/arch/powerpc/mm/mmap.c b/arch/powerpc/mm/mmap.c > index a5d9ef59debe..6141cfff634e 100644 > --- a/arch/powerpc/mm/mmap.c > +++ b/arch/powerpc/mm/mmap.c > @@ -59,13 +59,14 @@ static inline int mmap_is_legacy(void) > > unsigned long arch_mmap_rnd(void) > { > - unsigned long rnd; > + unsigned long shift, rnd; > > - /* 8MB for 32bit, 1GB for 64bit */ > + shift = mmap_rnd_bits; > +#ifdef CONFIG_COMPAT > if (is_32bit_task()) > - rnd = get_random_long() % (1<<(23-PAGE_SHIFT)); > - else > - rnd = get_random_long() % (1UL<<(30-PAGE_SHIFT)); > + shift = mmap_rnd_compat_bits; > +#endif > + rnd = get_random_long() % (1 << shift); > > return rnd << PAGE_SHIFT; > } > -- > 2.7.4 >
Michael Ellerman <mpe@ellerman.id.au> writes: > Add powerpc support for mmap_rnd_bits and mmap_rnd_compat_bits, which are two > sysctls that allow a user to configure the number of bits of randomness used for > ASLR. > > Because of the way the Kconfig for ARCH_MMAP_RND_BITS is defined, we have to > construct at least the MIN value in Kconfig, vs in a header which would be more > natural. Given that we just go ahead and do it all in Kconfig. > > At least according to the code (the documentation makes no mention of it), the > value is defined as the number of bits of randomisation *of the page*, not the > address. This makes some sense, with larger page sizes more of the low bits are > forced to zero, which would reduce the randomisation if we didn't take the > PAGE_SIZE into account. However it does mean the min/max values have to change > depending on the PAGE_SIZE in order to actually limit the amount of address > space consumed by the randomisation. > > The result of that is that we have to define the default values based on both > 32-bit vs 64-bit, but also the configured PAGE_SIZE. Furthermore now that we > have 128TB address space support on Book3S, we also have to take that into > account. > > Finally we can wire up the value in arch_mmap_rnd(). > > Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> > Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com> Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> > --- > arch/powerpc/Kconfig | 44 ++++++++++++++++++++++++++++++++++++++++++++ > arch/powerpc/mm/mmap.c | 11 ++++++----- > 2 files changed, 50 insertions(+), 5 deletions(-) > > v2: Fix the 32-bit MAX value incorrectly using MIN as spotted by Kees. > > Kees/Bhupesh, would love a Review/Ack/Tested-by from you, I'll plan to merge > this later today (Friday) my time. > > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig > index 97a8bc8a095c..6f0503951e94 100644 > --- a/arch/powerpc/Kconfig > +++ b/arch/powerpc/Kconfig > @@ -22,6 +22,48 @@ config MMU > bool > default y > > +config ARCH_MMAP_RND_BITS_MAX > + # On Book3S 64, the default virtual address space for 64-bit processes > + # is 2^47 (128TB). As a maximum, allow randomisation to consume up to > + # 32T of address space (2^45), which should ensure a reasonable gap > + # between bottom-up and top-down allocations for applications that > + # consume "normal" amounts of address space. Book3S 64 only supports 64K > + # and 4K page sizes. > + default 29 if PPC_BOOK3S_64 && PPC_64K_PAGES # 29 = 45 (32T) - 16 (64K) > + default 33 if PPC_BOOK3S_64 # 33 = 45 (32T) - 12 (4K) > + # > + # On all other 64-bit platforms (currently only Book3E), the virtual > + # address space is 2^46 (64TB). Allow randomisation to consume up to 16T > + # of address space (2^44). Only 4K page sizes are supported. > + default 32 if 64BIT # 32 = 44 (16T) - 12 (4K) > + # > + # For 32-bit, use the compat values, as they're the same. > + default ARCH_MMAP_RND_COMPAT_BITS_MAX > + > +config ARCH_MMAP_RND_BITS_MIN > + # Allow randomisation to consume up to 1GB of address space (2^30). > + default 14 if 64BIT && PPC_64K_PAGES # 14 = 30 (1GB) - 16 (64K) > + default 18 if 64BIT # 18 = 30 (1GB) - 12 (4K) > + # > + # For 32-bit, use the compat values, as they're the same. > + default ARCH_MMAP_RND_COMPAT_BITS_MIN > + > +config ARCH_MMAP_RND_COMPAT_BITS_MAX > + # Total virtual address space for 32-bit processes is 2^31 (2GB). > + # Allow randomisation to consume up to 512MB of address space (2^29). > + default 11 if PPC_256K_PAGES # 11 = 29 (512MB) - 18 (256K) > + default 13 if PPC_64K_PAGES # 13 = 29 (512MB) - 16 (64K) > + default 15 if PPC_16K_PAGES # 15 = 29 (512MB) - 14 (16K) > + default 17 # 17 = 29 (512MB) - 12 (4K) > + > +config ARCH_MMAP_RND_COMPAT_BITS_MIN > + # Total virtual address space for 32-bit processes is 2^31 (2GB). > + # Allow randomisation to consume up to 8MB of address space (2^23). > + default 5 if PPC_256K_PAGES # 5 = 23 (8MB) - 18 (256K) > + default 7 if PPC_64K_PAGES # 7 = 23 (8MB) - 16 (64K) > + default 9 if PPC_16K_PAGES # 9 = 23 (8MB) - 14 (16K) > + default 11 # 11 = 23 (8MB) - 12 (4K) > + > config HAVE_SETUP_PER_CPU_AREA > def_bool PPC64 > > @@ -120,6 +162,8 @@ config PPC > select HAVE_ARCH_HARDENED_USERCOPY > select HAVE_ARCH_JUMP_LABEL > select HAVE_ARCH_KGDB > + select HAVE_ARCH_MMAP_RND_BITS > + select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT > select HAVE_ARCH_SECCOMP_FILTER > select HAVE_ARCH_TRACEHOOK > select HAVE_CBPF_JIT if !PPC64 > diff --git a/arch/powerpc/mm/mmap.c b/arch/powerpc/mm/mmap.c > index a5d9ef59debe..6141cfff634e 100644 > --- a/arch/powerpc/mm/mmap.c > +++ b/arch/powerpc/mm/mmap.c > @@ -59,13 +59,14 @@ static inline int mmap_is_legacy(void) > > unsigned long arch_mmap_rnd(void) > { > - unsigned long rnd; > + unsigned long shift, rnd; > > - /* 8MB for 32bit, 1GB for 64bit */ > + shift = mmap_rnd_bits; > +#ifdef CONFIG_COMPAT > if (is_32bit_task()) > - rnd = get_random_long() % (1<<(23-PAGE_SHIFT)); > - else > - rnd = get_random_long() % (1UL<<(30-PAGE_SHIFT)); > + shift = mmap_rnd_compat_bits; > +#endif > + rnd = get_random_long() % (1 << shift); > > return rnd << PAGE_SHIFT; > } > -- > 2.7.4
Hi Michael, Thanks for the v2. It looks good. On Thu, Apr 20, 2017 at 8:06 PM, Michael Ellerman <mpe@ellerman.id.au> wrote: > Add powerpc support for mmap_rnd_bits and mmap_rnd_compat_bits, which are two > sysctls that allow a user to configure the number of bits of randomness used for > ASLR. > > Because of the way the Kconfig for ARCH_MMAP_RND_BITS is defined, we have to > construct at least the MIN value in Kconfig, vs in a header which would be more > natural. Given that we just go ahead and do it all in Kconfig. > > At least according to the code (the documentation makes no mention of it), the > value is defined as the number of bits of randomisation *of the page*, not the > address. This makes some sense, with larger page sizes more of the low bits are > forced to zero, which would reduce the randomisation if we didn't take the > PAGE_SIZE into account. However it does mean the min/max values have to change > depending on the PAGE_SIZE in order to actually limit the amount of address > space consumed by the randomisation. > > The result of that is that we have to define the default values based on both > 32-bit vs 64-bit, but also the configured PAGE_SIZE. Furthermore now that we > have 128TB address space support on Book3S, we also have to take that into > account. > > Finally we can wire up the value in arch_mmap_rnd(). > > Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> > Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com> > --- > arch/powerpc/Kconfig | 44 ++++++++++++++++++++++++++++++++++++++++++++ > arch/powerpc/mm/mmap.c | 11 ++++++----- > 2 files changed, 50 insertions(+), 5 deletions(-) > > v2: Fix the 32-bit MAX value incorrectly using MIN as spotted by Kees. > > Kees/Bhupesh, would love a Review/Ack/Tested-by from you, I'll plan to merge > this later today (Friday) my time. > > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig > index 97a8bc8a095c..6f0503951e94 100644 > --- a/arch/powerpc/Kconfig > +++ b/arch/powerpc/Kconfig > @@ -22,6 +22,48 @@ config MMU > bool > default y > > +config ARCH_MMAP_RND_BITS_MAX > + # On Book3S 64, the default virtual address space for 64-bit processes > + # is 2^47 (128TB). As a maximum, allow randomisation to consume up to > + # 32T of address space (2^45), which should ensure a reasonable gap > + # between bottom-up and top-down allocations for applications that > + # consume "normal" amounts of address space. Book3S 64 only supports 64K > + # and 4K page sizes. > + default 29 if PPC_BOOK3S_64 && PPC_64K_PAGES # 29 = 45 (32T) - 16 (64K) > + default 33 if PPC_BOOK3S_64 # 33 = 45 (32T) - 12 (4K) > + # > + # On all other 64-bit platforms (currently only Book3E), the virtual > + # address space is 2^46 (64TB). Allow randomisation to consume up to 16T > + # of address space (2^44). Only 4K page sizes are supported. > + default 32 if 64BIT # 32 = 44 (16T) - 12 (4K) > + # > + # For 32-bit, use the compat values, as they're the same. > + default ARCH_MMAP_RND_COMPAT_BITS_MAX > + > +config ARCH_MMAP_RND_BITS_MIN > + # Allow randomisation to consume up to 1GB of address space (2^30). > + default 14 if 64BIT && PPC_64K_PAGES # 14 = 30 (1GB) - 16 (64K) > + default 18 if 64BIT # 18 = 30 (1GB) - 12 (4K) > + # > + # For 32-bit, use the compat values, as they're the same. > + default ARCH_MMAP_RND_COMPAT_BITS_MIN > + > +config ARCH_MMAP_RND_COMPAT_BITS_MAX > + # Total virtual address space for 32-bit processes is 2^31 (2GB). > + # Allow randomisation to consume up to 512MB of address space (2^29). > + default 11 if PPC_256K_PAGES # 11 = 29 (512MB) - 18 (256K) > + default 13 if PPC_64K_PAGES # 13 = 29 (512MB) - 16 (64K) > + default 15 if PPC_16K_PAGES # 15 = 29 (512MB) - 14 (16K) > + default 17 # 17 = 29 (512MB) - 12 (4K) > + > +config ARCH_MMAP_RND_COMPAT_BITS_MIN > + # Total virtual address space for 32-bit processes is 2^31 (2GB). > + # Allow randomisation to consume up to 8MB of address space (2^23). > + default 5 if PPC_256K_PAGES # 5 = 23 (8MB) - 18 (256K) > + default 7 if PPC_64K_PAGES # 7 = 23 (8MB) - 16 (64K) > + default 9 if PPC_16K_PAGES # 9 = 23 (8MB) - 14 (16K) > + default 11 # 11 = 23 (8MB) - 12 (4K) > + > config HAVE_SETUP_PER_CPU_AREA > def_bool PPC64 > > @@ -120,6 +162,8 @@ config PPC > select HAVE_ARCH_HARDENED_USERCOPY > select HAVE_ARCH_JUMP_LABEL > select HAVE_ARCH_KGDB > + select HAVE_ARCH_MMAP_RND_BITS > + select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT > select HAVE_ARCH_SECCOMP_FILTER > select HAVE_ARCH_TRACEHOOK > select HAVE_CBPF_JIT if !PPC64 > diff --git a/arch/powerpc/mm/mmap.c b/arch/powerpc/mm/mmap.c > index a5d9ef59debe..6141cfff634e 100644 > --- a/arch/powerpc/mm/mmap.c > +++ b/arch/powerpc/mm/mmap.c > @@ -59,13 +59,14 @@ static inline int mmap_is_legacy(void) > > unsigned long arch_mmap_rnd(void) > { > - unsigned long rnd; > + unsigned long shift, rnd; > > - /* 8MB for 32bit, 1GB for 64bit */ > + shift = mmap_rnd_bits; > +#ifdef CONFIG_COMPAT > if (is_32bit_task()) > - rnd = get_random_long() % (1<<(23-PAGE_SHIFT)); > - else > - rnd = get_random_long() % (1UL<<(30-PAGE_SHIFT)); > + shift = mmap_rnd_compat_bits; > +#endif > + rnd = get_random_long() % (1 << shift); > > return rnd << PAGE_SHIFT; > } > -- > 2.7.4 I used a simple program to dump the load address used for a ASLR elf on the RHEL PPC64LE platform using the above patch: 1. Create a test PIE program which shows its own memory map: $ cat show_mmap_pie.c #include <stdlib.h> #include <stdio.h> int main(void){ char command[1024]; sprintf(command,"cat /proc/%d/maps",getpid()); system(command); return 0; } 2. Compile it as a PIE: $ gcc -o show_mmap_pie -fpie -pie show_mmap_pie.c 3. After applying the patch, we can increase the randomization range on RHEL PPC64LE system with 64K page size: # cat /proc/sys/vm/mmap_rnd_bits 14 # ./show_mmap_pie 4c050000-4c060000 r-xp 00000000 fd:00 102212985 /root/show_mmap_pie 4c060000-4c070000 r--p 00000000 fd:00 102212985 /root/show_mmap_pie 4c070000-4c080000 rw-p 00010000 fd:00 102212985 /root/show_mmap_pie 7fffa0460000-7fffa0620000 r-xp 00000000 fd:00 33617825 /usr/lib64/libc-2.17.so 7fffa0620000-7fffa0630000 r--p 001b0000 fd:00 33617825 /usr/lib64/libc-2.17.so 7fffa0630000-7fffa0640000 rw-p 001c0000 fd:00 33617825 /usr/lib64/libc-2.17.so 7fffa0650000-7fffa0670000 r-xp 00000000 00:00 0 [vdso] 7fffa0670000-7fffa06a0000 r-xp 00000000 fd:00 33617818 /usr/lib64/ld-2.17.so 7fffa06a0000-7fffa06b0000 r--p 00020000 fd:00 33617818 /usr/lib64/ld-2.17.so 7fffa06b0000-7fffa06c0000 rw-p 00030000 fd:00 33617818 /usr/lib64/ld-2.17.so 7fffe3fe0000-7fffe4010000 rw-p 00000000 00:00 0 [stack] # echo 28 > /proc/sys/vm/mmap_rnd_bits # ./show_mmap_pie 202e31d0000-202e31e0000 r-xp 00000000 fd:00 102212985 /root/show_mmap_pie 202e31e0000-202e31f0000 r--p 00000000 fd:00 102212985 /root/show_mmap_pie 202e31f0000-202e3200000 rw-p 00010000 fd:00 102212985 /root/show_mmap_pie 7ef112640000-7ef112800000 r-xp 00000000 fd:00 33617825 /usr/lib64/libc-2.17.so 7ef112800000-7ef112810000 r--p 001b0000 fd:00 33617825 /usr/lib64/libc-2.17.so 7ef112810000-7ef112820000 rw-p 001c0000 fd:00 33617825 /usr/lib64/libc-2.17.so 7ef112830000-7ef112850000 r-xp 00000000 00:00 0 [vdso] 7ef112850000-7ef112880000 r-xp 00000000 fd:00 33617818 /usr/lib64/ld-2.17.so 7ef112880000-7ef112890000 r--p 00020000 fd:00 33617818 /usr/lib64/ld-2.17.so 7ef112890000-7ef1128a0000 rw-p 00030000 fd:00 33617818 /usr/lib64/ld-2.17.so 7fffd3070000-7fffd30a0000 rw-p 00000000 00:00 0 [stack] So, you can add my Tested-by for this patch as well. Regards, Bhupesh
On Thu, 2017-04-20 at 14:36:20 UTC, Michael Ellerman wrote: > Add powerpc support for mmap_rnd_bits and mmap_rnd_compat_bits, which are two > sysctls that allow a user to configure the number of bits of randomness used for > ASLR. > > Because of the way the Kconfig for ARCH_MMAP_RND_BITS is defined, we have to > construct at least the MIN value in Kconfig, vs in a header which would be more > natural. Given that we just go ahead and do it all in Kconfig. > > At least according to the code (the documentation makes no mention of it), the > value is defined as the number of bits of randomisation *of the page*, not the > address. This makes some sense, with larger page sizes more of the low bits are > forced to zero, which would reduce the randomisation if we didn't take the > PAGE_SIZE into account. However it does mean the min/max values have to change > depending on the PAGE_SIZE in order to actually limit the amount of address > space consumed by the randomisation. > > The result of that is that we have to define the default values based on both > 32-bit vs 64-bit, but also the configured PAGE_SIZE. Furthermore now that we > have 128TB address space support on Book3S, we also have to take that into > account. > > Finally we can wire up the value in arch_mmap_rnd(). > > Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> > Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com> > Reviewed-by: Kees Cook <keescook@chromium.org> > Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Applied to powerpc next. https://git.kernel.org/powerpc/c/9fea59bd7ca541e5d0851f0b6dbca8 cheers
On Fri, 2017-04-21 at 00:36 +1000, Michael Ellerman wrote: > Add powerpc support for mmap_rnd_bits and mmap_rnd_compat_bits, which are two > sysctls that allow a user to configure the number of bits of randomness used for > ASLR. > > Because of the way the Kconfig for ARCH_MMAP_RND_BITS is defined, we have to > construct at least the MIN value in Kconfig, vs in a header which would be more > natural. Given that we just go ahead and do it all in Kconfig. > > At least according to the code (the documentation makes no mention of it), the > value is defined as the number of bits of randomisation *of the page*, not the > address. This makes some sense, with larger page sizes more of the low bits are > forced to zero, which would reduce the randomisation if we didn't take the > PAGE_SIZE into account. However it does mean the min/max values have to change > depending on the PAGE_SIZE in order to actually limit the amount of address > space consumed by the randomisation. > > The result of that is that we have to define the default values based on both > 32-bit vs 64-bit, but also the configured PAGE_SIZE. Furthermore now that we > have 128TB address space support on Book3S, we also have to take that into > account. Could we please suggest that this should not be sent to stable or back-ported as the 128T default is new? > > Finally we can wire up the value in arch_mmap_rnd(). > > Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> > Signed-off-by: Bhupesh Sharma <bhsharma@redhat.com> > --- > arch/powerpc/Kconfig | 44 ++++++++++++++++++++++++++++++++++++++++++++ > arch/powerpc/mm/mmap.c | 11 ++++++----- > 2 files changed, 50 insertions(+), 5 deletions(-) > > v2: Fix the 32-bit MAX value incorrectly using MIN as spotted by Kees. > > Kees/Bhupesh, would love a Review/Ack/Tested-by from you, I'll plan to merge > this later today (Friday) my time. > > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig > index 97a8bc8a095c..6f0503951e94 100644 > --- a/arch/powerpc/Kconfig > +++ b/arch/powerpc/Kconfig > @@ -22,6 +22,48 @@ config MMU > bool > default y > > +config ARCH_MMAP_RND_BITS_MAX > + # On Book3S 64, the default virtual address space for 64-bit processes > + # is 2^47 (128TB). As a maximum, allow randomisation to consume up to > + # 32T of address space (2^45), which should ensure a reasonable gap > + # between bottom-up and top-down allocations for applications that > + # consume "normal" amounts of address space. Book3S 64 only supports 64K > + # and 4K page sizes. > + default 29 if PPC_BOOK3S_64 && PPC_64K_PAGES # 29 = 45 (32T) - 16 (64K) > + default 33 if PPC_BOOK3S_64 # 33 = 45 (32T) - 12 (4K) > + # > + # On all other 64-bit platforms (currently only Book3E), the virtual > + # address space is 2^46 (64TB). Allow randomisation to consume up to 16T > + # of address space (2^44). Only 4K page sizes are supported. > + default 32 if 64BIT # 32 = 44 (16T) - 12 (4K) > + # > + # For 32-bit, use the compat values, as they're the same. > + default ARCH_MMAP_RND_COMPAT_BITS_MAX > + > +config ARCH_MMAP_RND_BITS_MIN > + # Allow randomisation to consume up to 1GB of address space (2^30). > + default 14 if 64BIT && PPC_64K_PAGES # 14 = 30 (1GB) - 16 (64K) > + default 18 if 64BIT # 18 = 30 (1GB) - 12 (4K) > + # > + # For 32-bit, use the compat values, as they're the same. > + default ARCH_MMAP_RND_COMPAT_BITS_MIN > + > +config ARCH_MMAP_RND_COMPAT_BITS_MAX > + # Total virtual address space for 32-bit processes is 2^31 (2GB). > + # Allow randomisation to consume up to 512MB of address space (2^29). > + default 11 if PPC_256K_PAGES # 11 = 29 (512MB) - 18 (256K) > + default 13 if PPC_64K_PAGES # 13 = 29 (512MB) - 16 (64K) > + default 15 if PPC_16K_PAGES # 15 = 29 (512MB) - 14 (16K) > + default 17 # 17 = 29 (512MB) - 12 (4K) > + > +config ARCH_MMAP_RND_COMPAT_BITS_MIN > + # Total virtual address space for 32-bit processes is 2^31 (2GB). > + # Allow randomisation to consume up to 8MB of address space (2^23). > + default 5 if PPC_256K_PAGES # 5 = 23 (8MB) - 18 (256K) > + default 7 if PPC_64K_PAGES # 7 = 23 (8MB) - 16 (64K) > + default 9 if PPC_16K_PAGES # 9 = 23 (8MB) - 14 (16K) > + default 11 # 11 = 23 (8MB) - 12 (4K) > + > config HAVE_SETUP_PER_CPU_AREA > def_bool PPC64 > > @@ -120,6 +162,8 @@ config PPC > select HAVE_ARCH_HARDENED_USERCOPY > select HAVE_ARCH_JUMP_LABEL > select HAVE_ARCH_KGDB > + select HAVE_ARCH_MMAP_RND_BITS > + select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT > select HAVE_ARCH_SECCOMP_FILTER > select HAVE_ARCH_TRACEHOOK > select HAVE_CBPF_JIT if !PPC64 > diff --git a/arch/powerpc/mm/mmap.c b/arch/powerpc/mm/mmap.c > index a5d9ef59debe..6141cfff634e 100644 > --- a/arch/powerpc/mm/mmap.c > +++ b/arch/powerpc/mm/mmap.c > @@ -59,13 +59,14 @@ static inline int mmap_is_legacy(void) > > unsigned long arch_mmap_rnd(void) > { > - unsigned long rnd; > + unsigned long shift, rnd; > > - /* 8MB for 32bit, 1GB for 64bit */ > + shift = mmap_rnd_bits; > +#ifdef CONFIG_COMPAT > if (is_32bit_task()) > - rnd = get_random_long() % (1<<(23-PAGE_SHIFT)); > - else > - rnd = get_random_long() % (1UL<<(30-PAGE_SHIFT)); > + shift = mmap_rnd_compat_bits; > +#endif > + rnd = get_random_long() % (1 << shift); > Nitpick, 1 should be 1UL? > return rnd << PAGE_SHIFT; > } Acked-by: Balbir Singh <bsingharora@gmail.com>
Balbir Singh <bsingharora@gmail.com> writes: > On Fri, 2017-04-21 at 00:36 +1000, Michael Ellerman wrote: >> Add powerpc support for mmap_rnd_bits and mmap_rnd_compat_bits, which are two >> sysctls that allow a user to configure the number of bits of randomness used for >> ASLR. ... > > Could we please suggest that this should not be sent to stable or back-ported > as the 128T default is new? I'm not sure I follow. I didn't tag it for stable. Do you mean we should explicitly mark it as not-for-stable? If someone sends it to stable@vger I'll be pinged before it goes in and nak it, if someone wants to backport it (incorrectly) to their own tree then good luck to them :) >> diff --git a/arch/powerpc/mm/mmap.c b/arch/powerpc/mm/mmap.c >> index a5d9ef59debe..6141cfff634e 100644 >> --- a/arch/powerpc/mm/mmap.c >> +++ b/arch/powerpc/mm/mmap.c >> @@ -59,13 +59,14 @@ static inline int mmap_is_legacy(void) >> >> unsigned long arch_mmap_rnd(void) >> { >> - unsigned long rnd; >> + unsigned long shift, rnd; >> >> - /* 8MB for 32bit, 1GB for 64bit */ >> + shift = mmap_rnd_bits; >> +#ifdef CONFIG_COMPAT >> if (is_32bit_task()) >> - rnd = get_random_long() % (1<<(23-PAGE_SHIFT)); >> - else >> - rnd = get_random_long() % (1UL<<(30-PAGE_SHIFT)); >> + shift = mmap_rnd_compat_bits; >> +#endif >> + rnd = get_random_long() % (1 << shift); > > Nitpick, 1 should be 1UL? No, shift can only be 29 at most IIRC? But it's a bit fragile, so I'll change it. cheers
On Mon, Apr 24, 2017 at 7:29 AM, Michael Ellerman <mpe@ellerman.id.au> wrote: > Balbir Singh <bsingharora@gmail.com> writes: > >> On Fri, 2017-04-21 at 00:36 +1000, Michael Ellerman wrote: >>> Add powerpc support for mmap_rnd_bits and mmap_rnd_compat_bits, which are two >>> sysctls that allow a user to configure the number of bits of randomness used for >>> ASLR. > ... >> >> Could we please suggest that this should not be sent to stable or back-ported >> as the 128T default is new? > > I'm not sure I follow. I didn't tag it for stable. Do you mean we should > explicitly mark it as not-for-stable? > > If someone sends it to stable@vger I'll be pinged before it goes in and > nak it, if someone wants to backport it (incorrectly) to their own tree > then good luck to them :) > >>> diff --git a/arch/powerpc/mm/mmap.c b/arch/powerpc/mm/mmap.c >>> index a5d9ef59debe..6141cfff634e 100644 >>> --- a/arch/powerpc/mm/mmap.c >>> +++ b/arch/powerpc/mm/mmap.c >>> @@ -59,13 +59,14 @@ static inline int mmap_is_legacy(void) >>> >>> unsigned long arch_mmap_rnd(void) >>> { >>> - unsigned long rnd; >>> + unsigned long shift, rnd; >>> >>> - /* 8MB for 32bit, 1GB for 64bit */ >>> + shift = mmap_rnd_bits; >>> +#ifdef CONFIG_COMPAT >>> if (is_32bit_task()) >>> - rnd = get_random_long() % (1<<(23-PAGE_SHIFT)); >>> - else >>> - rnd = get_random_long() % (1UL<<(30-PAGE_SHIFT)); >>> + shift = mmap_rnd_compat_bits; >>> +#endif >>> + rnd = get_random_long() % (1 << shift); >> >> Nitpick, 1 should be 1UL? Nice catch! > No, shift can only be 29 at most IIRC? The largest value in the kconfigs is 33? > But it's a bit fragile, so I'll change it. Thanks! -Kees
Kees Cook <keescook@chromium.org> writes: > On Mon, Apr 24, 2017 at 7:29 AM, Michael Ellerman <mpe@ellerman.id.au> wrote: >> Balbir Singh <bsingharora@gmail.com> writes: >>>> diff --git a/arch/powerpc/mm/mmap.c b/arch/powerpc/mm/mmap.c >>>> index a5d9ef59debe..6141cfff634e 100644 >>>> --- a/arch/powerpc/mm/mmap.c >>>> +++ b/arch/powerpc/mm/mmap.c >>>> @@ -59,13 +59,14 @@ static inline int mmap_is_legacy(void) >>>> >>>> unsigned long arch_mmap_rnd(void) >>>> { >>>> - unsigned long rnd; >>>> + unsigned long shift, rnd; >>>> >>>> - /* 8MB for 32bit, 1GB for 64bit */ >>>> + shift = mmap_rnd_bits; >>>> +#ifdef CONFIG_COMPAT >>>> if (is_32bit_task()) >>>> - rnd = get_random_long() % (1<<(23-PAGE_SHIFT)); >>>> - else >>>> - rnd = get_random_long() % (1UL<<(30-PAGE_SHIFT)); >>>> + shift = mmap_rnd_compat_bits; >>>> +#endif >>>> + rnd = get_random_long() % (1 << shift); >>> >>> Nitpick, 1 should be 1UL? > > Nice catch! > >> No, shift can only be 29 at most IIRC? > > The largest value in the kconfigs is 33? Yeah you're right, for the 4K page kernel it can be 33. Will fix. cheers
On Tue, 2017-04-25 at 00:29 +1000, Michael Ellerman wrote: > Balbir Singh <bsingharora@gmail.com> writes: > > > On Fri, 2017-04-21 at 00:36 +1000, Michael Ellerman wrote: > > > Add powerpc support for mmap_rnd_bits and mmap_rnd_compat_bits, which are two > > > sysctls that allow a user to configure the number of bits of randomness used for > > > ASLR. > > ... > > > > Could we please suggest that this should not be sent to stable or back-ported > > as the 128T default is new? > > I'm not sure I follow. I didn't tag it for stable. Do you mean we should > explicitly mark it as not-for-stable? > Yeah.. I am concerned someone might backport it without looking at the dependencies :) > If someone sends it to stable@vger I'll be pinged before it goes in and > nak it, if someone wants to backport it (incorrectly) to their own tree > then good luck to them :) Fair enough <snip> > > > + rnd = get_random_long() % (1 << shift); > > > > Nitpick, 1 should be 1UL? > > No, shift can only be 29 at most IIRC? > > But it's a bit fragile, so I'll change it. > > cheers Cheers and I agree with Kees, a lot of the arch_mmap_rnd() code is beginning to look similar :) Balbir Singh
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index 97a8bc8a095c..6f0503951e94 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -22,6 +22,48 @@ config MMU bool default y +config ARCH_MMAP_RND_BITS_MAX + # On Book3S 64, the default virtual address space for 64-bit processes + # is 2^47 (128TB). As a maximum, allow randomisation to consume up to + # 32T of address space (2^45), which should ensure a reasonable gap + # between bottom-up and top-down allocations for applications that + # consume "normal" amounts of address space. Book3S 64 only supports 64K + # and 4K page sizes. + default 29 if PPC_BOOK3S_64 && PPC_64K_PAGES # 29 = 45 (32T) - 16 (64K) + default 33 if PPC_BOOK3S_64 # 33 = 45 (32T) - 12 (4K) + # + # On all other 64-bit platforms (currently only Book3E), the virtual + # address space is 2^46 (64TB). Allow randomisation to consume up to 16T + # of address space (2^44). Only 4K page sizes are supported. + default 32 if 64BIT # 32 = 44 (16T) - 12 (4K) + # + # For 32-bit, use the compat values, as they're the same. + default ARCH_MMAP_RND_COMPAT_BITS_MAX + +config ARCH_MMAP_RND_BITS_MIN + # Allow randomisation to consume up to 1GB of address space (2^30). + default 14 if 64BIT && PPC_64K_PAGES # 14 = 30 (1GB) - 16 (64K) + default 18 if 64BIT # 18 = 30 (1GB) - 12 (4K) + # + # For 32-bit, use the compat values, as they're the same. + default ARCH_MMAP_RND_COMPAT_BITS_MIN + +config ARCH_MMAP_RND_COMPAT_BITS_MAX + # Total virtual address space for 32-bit processes is 2^31 (2GB). + # Allow randomisation to consume up to 512MB of address space (2^29). + default 11 if PPC_256K_PAGES # 11 = 29 (512MB) - 18 (256K) + default 13 if PPC_64K_PAGES # 13 = 29 (512MB) - 16 (64K) + default 15 if PPC_16K_PAGES # 15 = 29 (512MB) - 14 (16K) + default 17 # 17 = 29 (512MB) - 12 (4K) + +config ARCH_MMAP_RND_COMPAT_BITS_MIN + # Total virtual address space for 32-bit processes is 2^31 (2GB). + # Allow randomisation to consume up to 8MB of address space (2^23). + default 5 if PPC_256K_PAGES # 5 = 23 (8MB) - 18 (256K) + default 7 if PPC_64K_PAGES # 7 = 23 (8MB) - 16 (64K) + default 9 if PPC_16K_PAGES # 9 = 23 (8MB) - 14 (16K) + default 11 # 11 = 23 (8MB) - 12 (4K) + config HAVE_SETUP_PER_CPU_AREA def_bool PPC64 @@ -120,6 +162,8 @@ config PPC select HAVE_ARCH_HARDENED_USERCOPY select HAVE_ARCH_JUMP_LABEL select HAVE_ARCH_KGDB + select HAVE_ARCH_MMAP_RND_BITS + select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT select HAVE_ARCH_SECCOMP_FILTER select HAVE_ARCH_TRACEHOOK select HAVE_CBPF_JIT if !PPC64 diff --git a/arch/powerpc/mm/mmap.c b/arch/powerpc/mm/mmap.c index a5d9ef59debe..6141cfff634e 100644 --- a/arch/powerpc/mm/mmap.c +++ b/arch/powerpc/mm/mmap.c @@ -59,13 +59,14 @@ static inline int mmap_is_legacy(void) unsigned long arch_mmap_rnd(void) { - unsigned long rnd; + unsigned long shift, rnd; - /* 8MB for 32bit, 1GB for 64bit */ + shift = mmap_rnd_bits; +#ifdef CONFIG_COMPAT if (is_32bit_task()) - rnd = get_random_long() % (1<<(23-PAGE_SHIFT)); - else - rnd = get_random_long() % (1UL<<(30-PAGE_SHIFT)); + shift = mmap_rnd_compat_bits; +#endif + rnd = get_random_long() % (1 << shift); return rnd << PAGE_SHIFT; }