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[209.85.217.52]) by smtp.gmail.com with ESMTPSA id j11sm327889vkj.13.2019.04.17.22.17.44 for (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Wed, 17 Apr 2019 22:17:45 -0700 (PDT) Received: by mail-vs1-f52.google.com with SMTP id j184so480796vsd.11 for ; Wed, 17 Apr 2019 22:17:44 -0700 (PDT) X-Received: by 2002:a67:f849:: with SMTP id b9mr28803360vsp.188.1555564664290; Wed, 17 Apr 2019 22:17:44 -0700 (PDT) MIME-Version: 1.0 References: <20190417052247.17809-1-alex@ghiti.fr> <20190417052247.17809-5-alex@ghiti.fr> In-Reply-To: <20190417052247.17809-5-alex@ghiti.fr> From: Kees Cook Date: Thu, 18 Apr 2019 00:17:32 -0500 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v3 04/11] arm64, mm: Move generic mmap layout functions to mm To: Alexandre Ghiti Cc: Andrew Morton , Christoph Hellwig , Russell King , Catalin Marinas , Will Deacon , Ralf Baechle , Paul Burton , James Hogan , Palmer Dabbelt , Albert Ou , Alexander Viro , Luis Chamberlain , Kees Cook , LKML , linux-arm-kernel , linux-mips@vger.kernel.org, linux-riscv@lists.infradead.org, "linux-fsdevel@vger.kernel.org" , Linux-MM , Christoph Hellwig Content-Type: text/plain; charset="UTF-8" Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org ( On Wed, Apr 17, 2019 at 12:27 AM Alexandre Ghiti wrote: > > arm64 handles top-down mmap layout in a way that can be easily reused > by other architectures, so make it available in mm. > It then introduces a new config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT > that can be set by other architectures to benefit from those functions. > Note that this new config depends on MMU being enabled, if selected > without MMU support, a warning will be thrown. > > Suggested-by: Christoph Hellwig > Signed-off-by: Alexandre Ghiti > --- > arch/Kconfig | 8 ++++ > arch/arm64/Kconfig | 1 + > arch/arm64/include/asm/processor.h | 2 - > arch/arm64/mm/mmap.c | 76 ------------------------------ > kernel/sysctl.c | 6 ++- > mm/util.c | 74 ++++++++++++++++++++++++++++- > 6 files changed, 86 insertions(+), 81 deletions(-) > > diff --git a/arch/Kconfig b/arch/Kconfig > index 33687dddd86a..7c8965c64590 100644 > --- a/arch/Kconfig > +++ b/arch/Kconfig > @@ -684,6 +684,14 @@ config HAVE_ARCH_COMPAT_MMAP_BASES > and vice-versa 32-bit applications to call 64-bit mmap(). > Required for applications doing different bitness syscalls. > > +# This allows to use a set of generic functions to determine mmap base > +# address by giving priority to top-down scheme only if the process > +# is not in legacy mode (compat task, unlimited stack size or > +# sysctl_legacy_va_layout). > +config ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT > + bool > + depends on MMU I'd prefer the comment were moved to the help text. I would include any details about what the arch still needs to define. For example right now, I think STACK_RND_MASK is still needed. (Though I think a common one could be added for this series too...) > + > config HAVE_COPY_THREAD_TLS > bool > help > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 7e34b9eba5de..670719a26b45 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -66,6 +66,7 @@ config ARM64 > select ARCH_SUPPORTS_INT128 if GCC_VERSION >= 50000 || CC_IS_CLANG > select ARCH_SUPPORTS_NUMA_BALANCING > select ARCH_WANT_COMPAT_IPC_PARSE_VERSION > + select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT > select ARCH_WANT_FRAME_POINTERS > select ARCH_HAS_UBSAN_SANITIZE_ALL > select ARM_AMBA > diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h > index 5d9ce62bdebd..4de2a2fd605a 100644 > --- a/arch/arm64/include/asm/processor.h > +++ b/arch/arm64/include/asm/processor.h > @@ -274,8 +274,6 @@ static inline void spin_lock_prefetch(const void *ptr) > "nop") : : "p" (ptr)); > } > > -#define HAVE_ARCH_PICK_MMAP_LAYOUT > - > #endif > > extern unsigned long __ro_after_init signal_minsigstksz; /* sigframe size */ > diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c > index ac89686c4af8..c74224421216 100644 > --- a/arch/arm64/mm/mmap.c > +++ b/arch/arm64/mm/mmap.c > @@ -31,82 +31,6 @@ > > #include > > -/* > - * Leave enough space between the mmap area and the stack to honour ulimit in > - * the face of randomisation. > - */ This comment goes missing in the move... > -#define MIN_GAP (SZ_128M) > -#define MAX_GAP (STACK_TOP/6*5) > - > -static int mmap_is_legacy(struct rlimit *rlim_stack) > -{ > - if (current->personality & ADDR_COMPAT_LAYOUT) > - return 1; > - > - if (rlim_stack->rlim_cur == RLIM_INFINITY) > - return 1; > - > - return sysctl_legacy_va_layout; > -} > - > -unsigned long arch_mmap_rnd(void) > -{ > - unsigned long rnd; > - > -#ifdef CONFIG_COMPAT > - if (is_compat_task()) > - rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1); > - else > -#endif > - rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1); > - return rnd << PAGE_SHIFT; > -} > - > -static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack) > -{ > - unsigned long gap = rlim_stack->rlim_cur; > - unsigned long pad = stack_guard_gap; > - > - /* Account for stack randomization if necessary */ > - if (current->flags & PF_RANDOMIZE) > - pad += (STACK_RND_MASK << PAGE_SHIFT); > - > - /* Values close to RLIM_INFINITY can overflow. */ > - if (gap + pad > gap) > - gap += pad; > - > - if (gap < MIN_GAP) > - gap = MIN_GAP; > - else if (gap > MAX_GAP) > - gap = MAX_GAP; > - > - return PAGE_ALIGN(STACK_TOP - gap - rnd); > -} > - > -/* > - * This function, called very early during the creation of a new process VM > - * image, sets up which VM layout function to use: > - */ > -void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack) > -{ > - unsigned long random_factor = 0UL; > - > - if (current->flags & PF_RANDOMIZE) > - random_factor = arch_mmap_rnd(); > - > - /* > - * Fall back to the standard layout if the personality bit is set, or > - * if the expected stack growth is unlimited: > - */ > - if (mmap_is_legacy(rlim_stack)) { > - mm->mmap_base = TASK_UNMAPPED_BASE + random_factor; > - mm->get_unmapped_area = arch_get_unmapped_area; > - } else { > - mm->mmap_base = mmap_base(random_factor, rlim_stack); > - mm->get_unmapped_area = arch_get_unmapped_area_topdown; > - } > -} > - > /* > * You really shouldn't be using read() or write() on /dev/mem. This might go > * away in the future. > diff --git a/kernel/sysctl.c b/kernel/sysctl.c > index e5da394d1ca3..eb3414e78986 100644 > --- a/kernel/sysctl.c > +++ b/kernel/sysctl.c > @@ -269,7 +269,8 @@ extern struct ctl_table epoll_table[]; > extern struct ctl_table firmware_config_table[]; > #endif > > -#ifdef HAVE_ARCH_PICK_MMAP_LAYOUT > +#if defined(HAVE_ARCH_PICK_MMAP_LAYOUT) || \ > + defined(CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT) > int sysctl_legacy_va_layout; > #endif > > @@ -1564,7 +1565,8 @@ static struct ctl_table vm_table[] = { > .proc_handler = proc_dointvec, > .extra1 = &zero, > }, > -#ifdef HAVE_ARCH_PICK_MMAP_LAYOUT > +#if defined(HAVE_ARCH_PICK_MMAP_LAYOUT) || \ > + defined(CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT) > { > .procname = "legacy_va_layout", > .data = &sysctl_legacy_va_layout, > diff --git a/mm/util.c b/mm/util.c > index a54afb9b4faa..5c3393d32ed1 100644 > --- a/mm/util.c > +++ b/mm/util.c > @@ -15,7 +15,12 @@ > #include > #include > #include > +#include > +#include > #include > +#include > +#include > +#include > > #include > > @@ -313,7 +318,74 @@ unsigned long randomize_stack_top(unsigned long stack_top) > #endif > } > > -#if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT) > +#ifdef CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT > +#ifdef CONFIG_ARCH_HAS_ELF_RANDOMIZE I think CONFIG_ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT should select CONFIG_ARCH_HAS_ELF_RANDOMIZE. It would mean moving arch_randomize_brk() into this patch set too. For arm64 and arm, this is totally fine: they have identical logic. On MIPS this would mean bumping the randomization up: arm64 uses SZ_32M for 32-bit and SZ_1G for 64-bit. MIPS is 8M and 256M respectively. I don't see anything that indicates this would be a problem. *cross fingers* It looks like x86 would need bumping too: it uses 32M on both 32-bit and 64-bit. STACK_RND_MASK is the same though. > +unsigned long arch_mmap_rnd(void) > +{ > + unsigned long rnd; > + > +#ifdef CONFIG_COMPAT > + if (is_compat_task()) > + rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1); > + else > +#endif /* CONFIG_COMPAT */ The ifdefs on is_compat_task() are not needed: is_compat_task() returns 0 in the !CONFIG_COMPAT case. > + rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1); > + > + return rnd << PAGE_SHIFT; > +} > +#endif /* CONFIG_ARCH_HAS_ELF_RANDOMIZE */ > + > +static int mmap_is_legacy(struct rlimit *rlim_stack) > +{ > + if (current->personality & ADDR_COMPAT_LAYOUT) > + return 1; > + > + if (rlim_stack->rlim_cur == RLIM_INFINITY) > + return 1; > + > + return sysctl_legacy_va_layout; > +} > + > +#define MIN_GAP (SZ_128M) > +#define MAX_GAP (STACK_TOP / 6 * 5) > + > +static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack) > +{ > + unsigned long gap = rlim_stack->rlim_cur; > + unsigned long pad = stack_guard_gap; > + > + /* Account for stack randomization if necessary */ > + if (current->flags & PF_RANDOMIZE) > + pad += (STACK_RND_MASK << PAGE_SHIFT); > + > + /* Values close to RLIM_INFINITY can overflow. */ > + if (gap + pad > gap) > + gap += pad; > + > + if (gap < MIN_GAP) > + gap = MIN_GAP; > + else if (gap > MAX_GAP) > + gap = MAX_GAP; > + > + return PAGE_ALIGN(STACK_TOP - gap - rnd); > +} > + > +void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack) > +{ > + unsigned long random_factor = 0UL; > + > + if (current->flags & PF_RANDOMIZE) > + random_factor = arch_mmap_rnd(); > + > + if (mmap_is_legacy(rlim_stack)) { > + mm->mmap_base = TASK_UNMAPPED_BASE + random_factor; > + mm->get_unmapped_area = arch_get_unmapped_area; > + } else { > + mm->mmap_base = mmap_base(random_factor, rlim_stack); > + mm->get_unmapped_area = arch_get_unmapped_area_topdown; > + } > +} > +#elif defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT) > void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack) > { > mm->mmap_base = TASK_UNMAPPED_BASE; > -- > 2.20.1 > -- Kees Cook