| Message ID | 20241008-v5_user_cfi_series-v6-11-60d9fe073f37@rivosinc.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | riscv control-flow integrity for usermode | expand |
On Tue, Oct 08, 2024 at 03:36:53PM -0700, Deepak Gupta wrote: > `arch_calc_vm_prot_bits` is implemented on risc-v to return VM_READ | > VM_WRITE if PROT_WRITE is specified. Similarly `riscv_sys_mmap` is > updated to convert all incoming PROT_WRITE to (PROT_WRITE | PROT_READ). > This is to make sure that any existing apps using PROT_WRITE still work. > > Earlier `protection_map[VM_WRITE]` used to pick read-write PTE encodings. > Now `protection_map[VM_WRITE]` will always pick PAGE_SHADOWSTACK PTE > encodings for shadow stack. Above changes ensure that existing apps > continue to work because underneath kernel will be picking > `protection_map[VM_WRITE|VM_READ]` PTE encodings. > > Signed-off-by: Deepak Gupta <debug@rivosinc.com> > --- > arch/riscv/include/asm/mman.h | 24 ++++++++++++++++++++++++ > arch/riscv/include/asm/pgtable.h | 1 + > arch/riscv/kernel/sys_riscv.c | 10 ++++++++++ > arch/riscv/mm/init.c | 2 +- > mm/mmap.c | 1 + > 5 files changed, 37 insertions(+), 1 deletion(-) > > diff --git a/arch/riscv/include/asm/mman.h b/arch/riscv/include/asm/mman.h > new file mode 100644 > index 000000000000..ef9fedf32546 > --- /dev/null > +++ b/arch/riscv/include/asm/mman.h > @@ -0,0 +1,24 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef __ASM_MMAN_H__ > +#define __ASM_MMAN_H__ > + > +#include <linux/compiler.h> > +#include <linux/types.h> > +#include <uapi/asm/mman.h> > + > +static inline unsigned long arch_calc_vm_prot_bits(unsigned long prot, > + unsigned long pkey __always_unused) > +{ > + unsigned long ret = 0; > + > + /* > + * If PROT_WRITE was specified, force it to VM_READ | VM_WRITE. > + * Only VM_WRITE means shadow stack. > + */ > + if (prot & PROT_WRITE) > + ret = (VM_READ | VM_WRITE); > + return ret; > +} > +#define arch_calc_vm_prot_bits(prot, pkey) arch_calc_vm_prot_bits(prot, pkey) > + > +#endif /* ! __ASM_MMAN_H__ */ > diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h > index e79f15293492..4948a1f18ae8 100644 > --- a/arch/riscv/include/asm/pgtable.h > +++ b/arch/riscv/include/asm/pgtable.h > @@ -177,6 +177,7 @@ extern struct pt_alloc_ops pt_ops __meminitdata; > #define PAGE_READ_EXEC __pgprot(_PAGE_BASE | _PAGE_READ | _PAGE_EXEC) > #define PAGE_WRITE_EXEC __pgprot(_PAGE_BASE | _PAGE_READ | \ > _PAGE_EXEC | _PAGE_WRITE) > +#define PAGE_SHADOWSTACK __pgprot(_PAGE_BASE | _PAGE_WRITE) > > #define PAGE_COPY PAGE_READ > #define PAGE_COPY_EXEC PAGE_READ_EXEC > diff --git a/arch/riscv/kernel/sys_riscv.c b/arch/riscv/kernel/sys_riscv.c > index d77afe05578f..43a448bf254b 100644 > --- a/arch/riscv/kernel/sys_riscv.c > +++ b/arch/riscv/kernel/sys_riscv.c > @@ -7,6 +7,7 @@ > > #include <linux/syscalls.h> > #include <asm/cacheflush.h> > +#include <asm-generic/mman-common.h> > > static long riscv_sys_mmap(unsigned long addr, unsigned long len, > unsigned long prot, unsigned long flags, > @@ -16,6 +17,15 @@ static long riscv_sys_mmap(unsigned long addr, unsigned long len, > if (unlikely(offset & (~PAGE_MASK >> page_shift_offset))) > return -EINVAL; > > + /* > + * If PROT_WRITE is specified then extend that to PROT_READ > + * protection_map[VM_WRITE] is now going to select shadow stack encodings. > + * So specifying PROT_WRITE actually should select protection_map [VM_WRITE | VM_READ] > + * If user wants to create shadow stack then they should use `map_shadow_stack` syscall. > + */ > + if (unlikely((prot & PROT_WRITE) && !(prot & PROT_READ))) > + prot |= PROT_READ; > + > return ksys_mmap_pgoff(addr, len, prot, flags, fd, > offset >> (PAGE_SHIFT - page_shift_offset)); > } > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c > index 0e8c20adcd98..964810aeb405 100644 > --- a/arch/riscv/mm/init.c > +++ b/arch/riscv/mm/init.c > @@ -326,7 +326,7 @@ pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE); > static const pgprot_t protection_map[16] = { > [VM_NONE] = PAGE_NONE, > [VM_READ] = PAGE_READ, > - [VM_WRITE] = PAGE_COPY, > + [VM_WRITE] = PAGE_SHADOWSTACK, > [VM_WRITE | VM_READ] = PAGE_COPY, > [VM_EXEC] = PAGE_EXEC, > [VM_EXEC | VM_READ] = PAGE_READ_EXEC, > diff --git a/mm/mmap.c b/mm/mmap.c > index dd4b35a25aeb..b56f1e8cbfc6 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -47,6 +47,7 @@ > #include <linux/oom.h> > #include <linux/sched/mm.h> > #include <linux/ksm.h> > +#include <linux/processor.h> This seems benign enough, just wonder why you need it? > > #include <linux/uaccess.h> > #include <asm/cacheflush.h> > > -- > 2.45.0 >
On Wed, Oct 09, 2024 at 02:36:12PM +0100, Lorenzo Stoakes wrote: >On Tue, Oct 08, 2024 at 03:36:53PM -0700, Deepak Gupta wrote: >> `arch_calc_vm_prot_bits` is implemented on risc-v to return VM_READ | >> VM_WRITE if PROT_WRITE is specified. Similarly `riscv_sys_mmap` is >> updated to convert all incoming PROT_WRITE to (PROT_WRITE | PROT_READ). >> This is to make sure that any existing apps using PROT_WRITE still work. >> >> Earlier `protection_map[VM_WRITE]` used to pick read-write PTE encodings. >> Now `protection_map[VM_WRITE]` will always pick PAGE_SHADOWSTACK PTE >> encodings for shadow stack. Above changes ensure that existing apps >> continue to work because underneath kernel will be picking >> `protection_map[VM_WRITE|VM_READ]` PTE encodings. >> >> Signed-off-by: Deepak Gupta <debug@rivosinc.com> >> --- >> arch/riscv/include/asm/mman.h | 24 ++++++++++++++++++++++++ >> arch/riscv/include/asm/pgtable.h | 1 + >> arch/riscv/kernel/sys_riscv.c | 10 ++++++++++ >> arch/riscv/mm/init.c | 2 +- >> mm/mmap.c | 1 + >> 5 files changed, 37 insertions(+), 1 deletion(-) >> >> diff --git a/arch/riscv/include/asm/mman.h b/arch/riscv/include/asm/mman.h >> new file mode 100644 >> index 000000000000..ef9fedf32546 >> --- /dev/null >> +++ b/arch/riscv/include/asm/mman.h >> @@ -0,0 +1,24 @@ >> +/* SPDX-License-Identifier: GPL-2.0 */ >> +#ifndef __ASM_MMAN_H__ >> +#define __ASM_MMAN_H__ >> + >> +#include <linux/compiler.h> >> +#include <linux/types.h> >> +#include <uapi/asm/mman.h> >> + >> +static inline unsigned long arch_calc_vm_prot_bits(unsigned long prot, >> + unsigned long pkey __always_unused) >> +{ >> + unsigned long ret = 0; >> + >> + /* >> + * If PROT_WRITE was specified, force it to VM_READ | VM_WRITE. >> + * Only VM_WRITE means shadow stack. >> + */ >> + if (prot & PROT_WRITE) >> + ret = (VM_READ | VM_WRITE); >> + return ret; >> +} >> +#define arch_calc_vm_prot_bits(prot, pkey) arch_calc_vm_prot_bits(prot, pkey) >> + >> +#endif /* ! __ASM_MMAN_H__ */ >> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h >> index e79f15293492..4948a1f18ae8 100644 >> --- a/arch/riscv/include/asm/pgtable.h >> +++ b/arch/riscv/include/asm/pgtable.h >> @@ -177,6 +177,7 @@ extern struct pt_alloc_ops pt_ops __meminitdata; >> #define PAGE_READ_EXEC __pgprot(_PAGE_BASE | _PAGE_READ | _PAGE_EXEC) >> #define PAGE_WRITE_EXEC __pgprot(_PAGE_BASE | _PAGE_READ | \ >> _PAGE_EXEC | _PAGE_WRITE) >> +#define PAGE_SHADOWSTACK __pgprot(_PAGE_BASE | _PAGE_WRITE) >> >> #define PAGE_COPY PAGE_READ >> #define PAGE_COPY_EXEC PAGE_READ_EXEC >> diff --git a/arch/riscv/kernel/sys_riscv.c b/arch/riscv/kernel/sys_riscv.c >> index d77afe05578f..43a448bf254b 100644 >> --- a/arch/riscv/kernel/sys_riscv.c >> +++ b/arch/riscv/kernel/sys_riscv.c >> @@ -7,6 +7,7 @@ >> >> #include <linux/syscalls.h> >> #include <asm/cacheflush.h> >> +#include <asm-generic/mman-common.h> >> >> static long riscv_sys_mmap(unsigned long addr, unsigned long len, >> unsigned long prot, unsigned long flags, >> @@ -16,6 +17,15 @@ static long riscv_sys_mmap(unsigned long addr, unsigned long len, >> if (unlikely(offset & (~PAGE_MASK >> page_shift_offset))) >> return -EINVAL; >> >> + /* >> + * If PROT_WRITE is specified then extend that to PROT_READ >> + * protection_map[VM_WRITE] is now going to select shadow stack encodings. >> + * So specifying PROT_WRITE actually should select protection_map [VM_WRITE | VM_READ] >> + * If user wants to create shadow stack then they should use `map_shadow_stack` syscall. >> + */ >> + if (unlikely((prot & PROT_WRITE) && !(prot & PROT_READ))) >> + prot |= PROT_READ; >> + >> return ksys_mmap_pgoff(addr, len, prot, flags, fd, >> offset >> (PAGE_SHIFT - page_shift_offset)); >> } >> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c >> index 0e8c20adcd98..964810aeb405 100644 >> --- a/arch/riscv/mm/init.c >> +++ b/arch/riscv/mm/init.c >> @@ -326,7 +326,7 @@ pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE); >> static const pgprot_t protection_map[16] = { >> [VM_NONE] = PAGE_NONE, >> [VM_READ] = PAGE_READ, >> - [VM_WRITE] = PAGE_COPY, >> + [VM_WRITE] = PAGE_SHADOWSTACK, >> [VM_WRITE | VM_READ] = PAGE_COPY, >> [VM_EXEC] = PAGE_EXEC, >> [VM_EXEC | VM_READ] = PAGE_READ_EXEC, >> diff --git a/mm/mmap.c b/mm/mmap.c >> index dd4b35a25aeb..b56f1e8cbfc6 100644 >> --- a/mm/mmap.c >> +++ b/mm/mmap.c >> @@ -47,6 +47,7 @@ >> #include <linux/oom.h> >> #include <linux/sched/mm.h> >> #include <linux/ksm.h> >> +#include <linux/processor.h> > >This seems benign enough, just wonder why you need it? I think leftover from previous versions. Will remove it. Don't think its needed here anymore. > >> >> #include <linux/uaccess.h> >> #include <asm/cacheflush.h> >> >> -- >> 2.45.0 >>
diff --git a/arch/riscv/include/asm/mman.h b/arch/riscv/include/asm/mman.h new file mode 100644 index 000000000000..ef9fedf32546 --- /dev/null +++ b/arch/riscv/include/asm/mman.h @@ -0,0 +1,24 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __ASM_MMAN_H__ +#define __ASM_MMAN_H__ + +#include <linux/compiler.h> +#include <linux/types.h> +#include <uapi/asm/mman.h> + +static inline unsigned long arch_calc_vm_prot_bits(unsigned long prot, + unsigned long pkey __always_unused) +{ + unsigned long ret = 0; + + /* + * If PROT_WRITE was specified, force it to VM_READ | VM_WRITE. + * Only VM_WRITE means shadow stack. + */ + if (prot & PROT_WRITE) + ret = (VM_READ | VM_WRITE); + return ret; +} +#define arch_calc_vm_prot_bits(prot, pkey) arch_calc_vm_prot_bits(prot, pkey) + +#endif /* ! __ASM_MMAN_H__ */ diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h index e79f15293492..4948a1f18ae8 100644 --- a/arch/riscv/include/asm/pgtable.h +++ b/arch/riscv/include/asm/pgtable.h @@ -177,6 +177,7 @@ extern struct pt_alloc_ops pt_ops __meminitdata; #define PAGE_READ_EXEC __pgprot(_PAGE_BASE | _PAGE_READ | _PAGE_EXEC) #define PAGE_WRITE_EXEC __pgprot(_PAGE_BASE | _PAGE_READ | \ _PAGE_EXEC | _PAGE_WRITE) +#define PAGE_SHADOWSTACK __pgprot(_PAGE_BASE | _PAGE_WRITE) #define PAGE_COPY PAGE_READ #define PAGE_COPY_EXEC PAGE_READ_EXEC diff --git a/arch/riscv/kernel/sys_riscv.c b/arch/riscv/kernel/sys_riscv.c index d77afe05578f..43a448bf254b 100644 --- a/arch/riscv/kernel/sys_riscv.c +++ b/arch/riscv/kernel/sys_riscv.c @@ -7,6 +7,7 @@ #include <linux/syscalls.h> #include <asm/cacheflush.h> +#include <asm-generic/mman-common.h> static long riscv_sys_mmap(unsigned long addr, unsigned long len, unsigned long prot, unsigned long flags, @@ -16,6 +17,15 @@ static long riscv_sys_mmap(unsigned long addr, unsigned long len, if (unlikely(offset & (~PAGE_MASK >> page_shift_offset))) return -EINVAL; + /* + * If PROT_WRITE is specified then extend that to PROT_READ + * protection_map[VM_WRITE] is now going to select shadow stack encodings. + * So specifying PROT_WRITE actually should select protection_map [VM_WRITE | VM_READ] + * If user wants to create shadow stack then they should use `map_shadow_stack` syscall. + */ + if (unlikely((prot & PROT_WRITE) && !(prot & PROT_READ))) + prot |= PROT_READ; + return ksys_mmap_pgoff(addr, len, prot, flags, fd, offset >> (PAGE_SHIFT - page_shift_offset)); } diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c index 0e8c20adcd98..964810aeb405 100644 --- a/arch/riscv/mm/init.c +++ b/arch/riscv/mm/init.c @@ -326,7 +326,7 @@ pgd_t early_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE); static const pgprot_t protection_map[16] = { [VM_NONE] = PAGE_NONE, [VM_READ] = PAGE_READ, - [VM_WRITE] = PAGE_COPY, + [VM_WRITE] = PAGE_SHADOWSTACK, [VM_WRITE | VM_READ] = PAGE_COPY, [VM_EXEC] = PAGE_EXEC, [VM_EXEC | VM_READ] = PAGE_READ_EXEC, diff --git a/mm/mmap.c b/mm/mmap.c index dd4b35a25aeb..b56f1e8cbfc6 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -47,6 +47,7 @@ #include <linux/oom.h> #include <linux/sched/mm.h> #include <linux/ksm.h> +#include <linux/processor.h> #include <linux/uaccess.h> #include <asm/cacheflush.h>
`arch_calc_vm_prot_bits` is implemented on risc-v to return VM_READ | VM_WRITE if PROT_WRITE is specified. Similarly `riscv_sys_mmap` is updated to convert all incoming PROT_WRITE to (PROT_WRITE | PROT_READ). This is to make sure that any existing apps using PROT_WRITE still work. Earlier `protection_map[VM_WRITE]` used to pick read-write PTE encodings. Now `protection_map[VM_WRITE]` will always pick PAGE_SHADOWSTACK PTE encodings for shadow stack. Above changes ensure that existing apps continue to work because underneath kernel will be picking `protection_map[VM_WRITE|VM_READ]` PTE encodings. Signed-off-by: Deepak Gupta <debug@rivosinc.com> --- arch/riscv/include/asm/mman.h | 24 ++++++++++++++++++++++++ arch/riscv/include/asm/pgtable.h | 1 + arch/riscv/kernel/sys_riscv.c | 10 ++++++++++ arch/riscv/mm/init.c | 2 +- mm/mmap.c | 1 + 5 files changed, 37 insertions(+), 1 deletion(-)