| Message ID | 20250204-v5_user_cfi_series-v9-1-b37a49c5205c@rivosinc.com |
|---|---|
| State | New |
| Headers | show |
| Series | riscv control-flow integrity for usermode | expand |
On Fri, Feb 07, 2025 at 08:06:59PM +0000, Mark Brown wrote: >On Fri, Feb 07, 2025 at 10:27:10AM +0100, Vlastimil Babka wrote: >> On 2/5/25 02:21, Deepak Gupta wrote: >> > VM_SHADOW_STACK (alias to VM_HIGH_ARCH_5) is used to encode shadow stack > >> I see that arm GCS uses VM_HIGH_ARCH_6. > >That'll be bitrot in the changelog, it was originally VM_HIGH_ARCH_5 on >arm64 as well but we had to renumber due to the addition of >VM_MTE_ALLOWED while the GCS series was on the list. The changelog just >shouldn't mention VM_HIGH_ARCH_x, it's not particularly relevant here. Yeah noted. Thanks.
On Fri, Feb 07, 2025 at 10:27:10AM +0100, Vlastimil Babka wrote: >On 2/5/25 02:21, Deepak Gupta wrote: >> VM_SHADOW_STACK (alias to VM_HIGH_ARCH_5) is used to encode shadow stack > >I see that arm GCS uses VM_HIGH_ARCH_6. > >> VMA on three architectures (x86 shadow stack, arm GCS and RISC-V shadow > >And RISC-V doesn't define it at all, not even in this patchset, or did I >miss it somewhere? > hmm... Something wrong in my workflow and rebasing. Thanks for catching this. >> stack). In case architecture doesn't implement shadow stack, it's VM_NONE >> Introducing a helper `is_shadow_stack_vma` to determine shadow stack vma >> or not. > >This looks like an unfinished sentence. As if it was to continue with "... >will allow us to ..." what? > >I'm not against a helper but this changelog is rather confusing and also >code in arch/x86 and arch/arm64 isn't converted to the helper but testing >VM_SHADOW_STACK still. > >> Signed-off-by: Deepak Gupta <debug@rivosinc.com> >> Reviewed-by: Mark Brown <broonie@kernel.org> >> --- >> mm/gup.c | 2 +- >> mm/mmap.c | 2 +- >> mm/vma.h | 10 +++++++--- >> 3 files changed, 9 insertions(+), 5 deletions(-) >> >> diff --git a/mm/gup.c b/mm/gup.c >> index 3883b307780e..8c64f3ff34ab 100644 >> --- a/mm/gup.c >> +++ b/mm/gup.c >> @@ -1291,7 +1291,7 @@ static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags) >> !writable_file_mapping_allowed(vma, gup_flags)) >> return -EFAULT; >> >> - if (!(vm_flags & VM_WRITE) || (vm_flags & VM_SHADOW_STACK)) { >> + if (!(vm_flags & VM_WRITE) || is_shadow_stack_vma(vm_flags)) { >> if (!(gup_flags & FOLL_FORCE)) >> return -EFAULT; >> /* >> diff --git a/mm/mmap.c b/mm/mmap.c >> index cda01071c7b1..7b6be4eec35d 100644 >> --- a/mm/mmap.c >> +++ b/mm/mmap.c >> @@ -648,7 +648,7 @@ SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg) >> */ >> static inline unsigned long stack_guard_placement(vm_flags_t vm_flags) >> { >> - if (vm_flags & VM_SHADOW_STACK) >> + if (is_shadow_stack_vma(vm_flags)) >> return PAGE_SIZE; >> >> return 0; >> diff --git a/mm/vma.h b/mm/vma.h >> index a2e8710b8c47..47482a25f5c3 100644 >> --- a/mm/vma.h >> +++ b/mm/vma.h >> @@ -278,7 +278,7 @@ static inline struct vm_area_struct *vma_prev_limit(struct vma_iterator *vmi, >> } >> >> /* >> - * These three helpers classifies VMAs for virtual memory accounting. >> + * These four helpers classifies VMAs for virtual memory accounting. >> */ >> >> /* >> @@ -289,6 +289,11 @@ static inline bool is_exec_mapping(vm_flags_t flags) >> return (flags & (VM_EXEC | VM_WRITE | VM_STACK)) == VM_EXEC; >> } >> >> +static inline bool is_shadow_stack_vma(vm_flags_t vm_flags) >> +{ >> + return !!(vm_flags & VM_SHADOW_STACK); >> +} >> + >> /* >> * Stack area (including shadow stacks) >> * >> @@ -297,7 +302,7 @@ static inline bool is_exec_mapping(vm_flags_t flags) >> */ >> static inline bool is_stack_mapping(vm_flags_t flags) >> { >> - return ((flags & VM_STACK) == VM_STACK) || (flags & VM_SHADOW_STACK); >> + return ((flags & VM_STACK) == VM_STACK) || is_shadow_stack_vma(flags); >> } >> >> /* >> @@ -308,7 +313,6 @@ static inline bool is_data_mapping(vm_flags_t flags) >> return (flags & (VM_WRITE | VM_SHARED | VM_STACK)) == VM_WRITE; >> } >> >> - >> static inline void vma_iter_config(struct vma_iterator *vmi, >> unsigned long index, unsigned long last) >> { >> >
On Fri, Feb 07, 2025 at 03:44:27PM -0800, Deepak Gupta wrote: >On Fri, Feb 07, 2025 at 10:27:10AM +0100, Vlastimil Babka wrote: >>On 2/5/25 02:21, Deepak Gupta wrote: >>>VM_SHADOW_STACK (alias to VM_HIGH_ARCH_5) is used to encode shadow stack >> >>I see that arm GCS uses VM_HIGH_ARCH_6. >> >>>VMA on three architectures (x86 shadow stack, arm GCS and RISC-V shadow >> >>And RISC-V doesn't define it at all, not even in this patchset, or did I >>miss it somewhere? >> > >hmm... >Something wrong in my workflow and rebasing. >Thanks for catching this. I think this is the miss on my part. I had this patch in last series which introduces `ARCH_HAS_USER_SHADOW_STACK` https://lore.kernel.org/all/20241111-v5_user_cfi_series-v8-1-dce14aa30207@rivosinc.com/ As part of above patch, `CONFIG_X86_USER_SHADOW_STACK` was replaced with `CONFIG_ARCH_HAS_USER_SHADOW_STACK` in `mm.h` to define VM_SHADOW_STACK as VM_HIGH_ARCH_5. It was all fine because all 3 arches were using VM_HIGH_ARCH_5. However as things progressed on, arm64 ended up using VM_HIGH_ARCH_6. But arm64 gcs patches also landed the introduction of `ARCH_HAS_USER_SHADOW_STACK`. So I dropped this patch from my v9 and didn't pay attention and actually missed the definition. > >>>stack). In case architecture doesn't implement shadow stack, it's VM_NONE >>>Introducing a helper `is_shadow_stack_vma` to determine shadow stack vma >>>or not.
diff --git a/mm/gup.c b/mm/gup.c index 3883b307780e..8c64f3ff34ab 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1291,7 +1291,7 @@ static int check_vma_flags(struct vm_area_struct *vma, unsigned long gup_flags) !writable_file_mapping_allowed(vma, gup_flags)) return -EFAULT; - if (!(vm_flags & VM_WRITE) || (vm_flags & VM_SHADOW_STACK)) { + if (!(vm_flags & VM_WRITE) || is_shadow_stack_vma(vm_flags)) { if (!(gup_flags & FOLL_FORCE)) return -EFAULT; /* diff --git a/mm/mmap.c b/mm/mmap.c index cda01071c7b1..7b6be4eec35d 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -648,7 +648,7 @@ SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg) */ static inline unsigned long stack_guard_placement(vm_flags_t vm_flags) { - if (vm_flags & VM_SHADOW_STACK) + if (is_shadow_stack_vma(vm_flags)) return PAGE_SIZE; return 0; diff --git a/mm/vma.h b/mm/vma.h index a2e8710b8c47..47482a25f5c3 100644 --- a/mm/vma.h +++ b/mm/vma.h @@ -278,7 +278,7 @@ static inline struct vm_area_struct *vma_prev_limit(struct vma_iterator *vmi, } /* - * These three helpers classifies VMAs for virtual memory accounting. + * These four helpers classifies VMAs for virtual memory accounting. */ /* @@ -289,6 +289,11 @@ static inline bool is_exec_mapping(vm_flags_t flags) return (flags & (VM_EXEC | VM_WRITE | VM_STACK)) == VM_EXEC; } +static inline bool is_shadow_stack_vma(vm_flags_t vm_flags) +{ + return !!(vm_flags & VM_SHADOW_STACK); +} + /* * Stack area (including shadow stacks) * @@ -297,7 +302,7 @@ static inline bool is_exec_mapping(vm_flags_t flags) */ static inline bool is_stack_mapping(vm_flags_t flags) { - return ((flags & VM_STACK) == VM_STACK) || (flags & VM_SHADOW_STACK); + return ((flags & VM_STACK) == VM_STACK) || is_shadow_stack_vma(flags); } /* @@ -308,7 +313,6 @@ static inline bool is_data_mapping(vm_flags_t flags) return (flags & (VM_WRITE | VM_SHARED | VM_STACK)) == VM_WRITE; } - static inline void vma_iter_config(struct vma_iterator *vmi, unsigned long index, unsigned long last) {