| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Date: Fri, 10 May 2024 14:02:54 -0700
From: Charlie Jenkins <charlie@...osinc.com>
To: Deepak Gupta <debug@...osinc.com>
Cc: paul.walmsley@...ive.com, rick.p.edgecombe@...el.com,
broonie@...nel.org, Szabolcs.Nagy@....com, kito.cheng@...ive.com,
keescook@...omium.org, ajones@...tanamicro.com,
conor.dooley@...rochip.com, cleger@...osinc.com,
atishp@...shpatra.org, alex@...ti.fr, bjorn@...osinc.com,
alexghiti@...osinc.com, samuel.holland@...ive.com, conor@...nel.org,
linux-doc@...r.kernel.org, linux-riscv@...ts.infradead.org,
linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
linux-mm@...ck.org, linux-arch@...r.kernel.org,
linux-kselftest@...r.kernel.org, corbet@....net, palmer@...belt.com,
aou@...s.berkeley.edu, robh+dt@...nel.org,
krzysztof.kozlowski+dt@...aro.org, oleg@...hat.com,
akpm@...ux-foundation.org, arnd@...db.de, ebiederm@...ssion.com,
Liam.Howlett@...cle.com, vbabka@...e.cz, lstoakes@...il.com,
shuah@...nel.org, brauner@...nel.org, andy.chiu@...ive.com,
jerry.shih@...ive.com, hankuan.chen@...ive.com,
greentime.hu@...ive.com, evan@...osinc.com, xiao.w.wang@...el.com,
apatel@...tanamicro.com, mchitale@...tanamicro.com,
dbarboza@...tanamicro.com, sameo@...osinc.com,
shikemeng@...weicloud.com, willy@...radead.org,
vincent.chen@...ive.com, guoren@...nel.org, samitolvanen@...gle.com,
songshuaishuai@...ylab.org, gerg@...nel.org, heiko@...ech.de,
bhe@...hat.com, jeeheng.sia@...rfivetech.com, cyy@...self.name,
maskray@...gle.com, ancientmodern4@...il.com,
mathis.salmen@...sal.de, cuiyunhui@...edance.com,
bgray@...ux.ibm.com, mpe@...erman.id.au, baruch@...s.co.il,
alx@...nel.org, david@...hat.com, catalin.marinas@....com,
revest@...omium.org, josh@...htriplett.org, shr@...kernel.io,
deller@....de, omosnace@...hat.com, ojeda@...nel.org,
jhubbard@...dia.com
Subject: Re: [PATCH v3 10/29] riscv/mm : ensure PROT_WRITE leads to VM_READ |
VM_WRITE
On Wed, Apr 03, 2024 at 04:34:58PM -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@...osinc.com>
> ---
> arch/riscv/include/asm/mman.h | 24 ++++++++++++++++++++++++
> arch/riscv/include/asm/pgtable.h | 1 +
> arch/riscv/kernel/sys_riscv.c | 11 +++++++++++
> arch/riscv/mm/init.c | 2 +-
> mm/mmap.c | 1 +
> 5 files changed, 38 insertions(+), 1 deletion(-)
> create mode 100644 arch/riscv/include/asm/mman.h
>
> 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 6066822e7396..4d5983bc6766 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -184,6 +184,7 @@ extern struct pt_alloc_ops pt_ops __initdata;
> #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 f1c1416a9f1e..846c36b1b3d5 100644
> --- a/arch/riscv/kernel/sys_riscv.c
> +++ b/arch/riscv/kernel/sys_riscv.c
> @@ -8,6 +8,8 @@
> #include <linux/syscalls.h>
> #include <asm/cacheflush.h>
> #include <asm-generic/mman-common.h>
> +#include <vdso/vsyscall.h>
> +#include <asm/mman.h>
>
> static long riscv_sys_mmap(unsigned long addr, unsigned long len,
> unsigned long prot, unsigned long flags,
> @@ -17,6 +19,15 @@ static long riscv_sys_mmap(unsigned long addr, unsigned long len,
> if (unlikely(offset & (~PAGE_MASK >> page_shift_offset)))
> return -EINVAL;
>
> + /*
> + * If only 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)))
The comments says that this should extend to PROT_READ if only
PROT_WRITE is specified. This condition instead is checking if
PROT_WRITE is selected but PROT_READ is not. If prot is (VM_EXEC |
VM_WRITE) then it would be extended to (VM_EXEC | VM_WRITE | VM_READ).
This will not currently cause any issues because these both map to the
same value in the protection_map PAGE_COPY_EXEC, however this seems to
be not the intention of this change.
prot == PROT_WRITE better suits the condition explained in the comment.
> + 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 fa34cf55037b..98e5ece4052a 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -299,7 +299,7 @@ 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 d89770eaab6b..57a974f49b00 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>
It doesn't seem like this is necessary for this patch.
- Charlie
>
> #include <linux/uaccess.h>
> #include <asm/cacheflush.h>
> --
> 2.43.2
>
Powered by blists - more mailing lists