| Message ID | 85ecef50788a3915a9a8fb52e97207901f27b057.1640036051.git.andreyknvl@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | kasan, vmalloc, arm64: add vmalloc tagging support for SW/HW_TAGS | expand |
On Mon, Dec 20, 2021 at 11:02 PM <andrey.konovalov@linux.dev> wrote: > > From: Andrey Konovalov <andreyknvl@google.com> > > Besides asking vmalloc memory to be executable via the prot argument > of __vmalloc_node_range() (see the previous patch), the kernel can skip > that bit and instead mark memory as executable via set_memory_x(). > > Once tag-based KASAN modes start tagging vmalloc allocations, executing > code from such allocations will lead to the PC register getting a tag, > which is not tolerated by the kernel. > > Generic kernel code typically allocates memory via module_alloc() if > it intends to mark memory as executable. (On arm64 module_alloc() > uses __vmalloc_node_range() without setting the executable bit). > > Thus, reset pointer tags of pointers returned from module_alloc(). > > However, on arm64 there's an exception: the eBPF subsystem. Instead of > using module_alloc(), it uses vmalloc() (via bpf_jit_alloc_exec()) > to allocate its JIT region. > > Thus, reset pointer tags of pointers returned from bpf_jit_alloc_exec(). > > Resetting tags for these pointers results in untagged pointers being > passed to set_memory_x(). This causes conflicts in arithmetic checks > in change_memory_common(), as vm_struct->addr pointer returned by > find_vm_area() is tagged. > > Reset pointer tag of find_vm_area(addr)->addr in change_memory_common(). > > Signed-off-by: Andrey Konovalov <andreyknvl@google.com> > > --- > > Changes v3->v4: > - Reset pointer tag in change_memory_common(). > > Changes v2->v3: > - Add this patch. > --- > arch/arm64/kernel/module.c | 3 ++- > arch/arm64/mm/pageattr.c | 2 +- > arch/arm64/net/bpf_jit_comp.c | 3 ++- > 3 files changed, 5 insertions(+), 3 deletions(-) > > diff --git a/arch/arm64/kernel/module.c b/arch/arm64/kernel/module.c > index d3a1fa818348..f2d4bb14bfab 100644 > --- a/arch/arm64/kernel/module.c > +++ b/arch/arm64/kernel/module.c > @@ -63,7 +63,8 @@ void *module_alloc(unsigned long size) > return NULL; > } > > - return p; > + /* Memory is intended to be executable, reset the pointer tag. */ > + return kasan_reset_tag(p); > } > > enum aarch64_reloc_op { > diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c > index a3bacd79507a..64e985eaa52d 100644 > --- a/arch/arm64/mm/pageattr.c > +++ b/arch/arm64/mm/pageattr.c > @@ -85,7 +85,7 @@ static int change_memory_common(unsigned long addr, int numpages, > */ > area = find_vm_area((void *)addr); > if (!area || > - end > (unsigned long)area->addr + area->size || > + end > (unsigned long)kasan_reset_tag(area->addr) + area->size || > !(area->flags & VM_ALLOC)) > return -EINVAL; > > diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c > index 07aad85848fa..381a67922c2d 100644 > --- a/arch/arm64/net/bpf_jit_comp.c > +++ b/arch/arm64/net/bpf_jit_comp.c > @@ -1147,7 +1147,8 @@ u64 bpf_jit_alloc_exec_limit(void) > > void *bpf_jit_alloc_exec(unsigned long size) > { > - return vmalloc(size); > + /* Memory is intended to be executable, reset the pointer tag. */ > + return kasan_reset_tag(vmalloc(size)); > } > > void bpf_jit_free_exec(void *addr) > -- > 2.25.1 Hi Catalin, I had to change this patch to fix an issue I discovered during testing. Could you PTAL once again? Thanks!
On Mon, Dec 20, 2021 at 11:02:04PM +0100, andrey.konovalov@linux.dev wrote: > From: Andrey Konovalov <andreyknvl@google.com> > > Besides asking vmalloc memory to be executable via the prot argument > of __vmalloc_node_range() (see the previous patch), the kernel can skip > that bit and instead mark memory as executable via set_memory_x(). > > Once tag-based KASAN modes start tagging vmalloc allocations, executing > code from such allocations will lead to the PC register getting a tag, > which is not tolerated by the kernel. > > Generic kernel code typically allocates memory via module_alloc() if > it intends to mark memory as executable. (On arm64 module_alloc() > uses __vmalloc_node_range() without setting the executable bit). > > Thus, reset pointer tags of pointers returned from module_alloc(). > > However, on arm64 there's an exception: the eBPF subsystem. Instead of > using module_alloc(), it uses vmalloc() (via bpf_jit_alloc_exec()) > to allocate its JIT region. > > Thus, reset pointer tags of pointers returned from bpf_jit_alloc_exec(). > > Resetting tags for these pointers results in untagged pointers being > passed to set_memory_x(). This causes conflicts in arithmetic checks > in change_memory_common(), as vm_struct->addr pointer returned by > find_vm_area() is tagged. > > Reset pointer tag of find_vm_area(addr)->addr in change_memory_common(). > > Signed-off-by: Andrey Konovalov <andreyknvl@google.com> > Acked-by: Catalin Marinas <catalin.marinas@arm.com>
diff --git a/arch/arm64/kernel/module.c b/arch/arm64/kernel/module.c index d3a1fa818348..f2d4bb14bfab 100644 --- a/arch/arm64/kernel/module.c +++ b/arch/arm64/kernel/module.c @@ -63,7 +63,8 @@ void *module_alloc(unsigned long size) return NULL; } - return p; + /* Memory is intended to be executable, reset the pointer tag. */ + return kasan_reset_tag(p); } enum aarch64_reloc_op { diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c index a3bacd79507a..64e985eaa52d 100644 --- a/arch/arm64/mm/pageattr.c +++ b/arch/arm64/mm/pageattr.c @@ -85,7 +85,7 @@ static int change_memory_common(unsigned long addr, int numpages, */ area = find_vm_area((void *)addr); if (!area || - end > (unsigned long)area->addr + area->size || + end > (unsigned long)kasan_reset_tag(area->addr) + area->size || !(area->flags & VM_ALLOC)) return -EINVAL; diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index 07aad85848fa..381a67922c2d 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -1147,7 +1147,8 @@ u64 bpf_jit_alloc_exec_limit(void) void *bpf_jit_alloc_exec(unsigned long size) { - return vmalloc(size); + /* Memory is intended to be executable, reset the pointer tag. */ + return kasan_reset_tag(vmalloc(size)); } void bpf_jit_free_exec(void *addr)