Re: [PATCH] x86/hugetlb: Use 32/64 mmap bases according to syscall

[Dmitry Safonov <dsafonov@virtuozzo.com>]

On 03/14/2017 02:41 PM, Dmitry Safonov wrote:
> Commit:
>   1b028f784e8c ("x86/mm: Introduce mmap_compat_base() for 32-bit
> mmap()")
>
> introduced two mmap() bases for 32-bit syscalls and for 64-bit syscalls.
> After that commit mm->mmap_base has address to base allocations for
> 64-bit syscalls, while mm->mmap_compat_base - for 32-bit syscalls.
> mmap() code was changed accordingly, but hugetlb code was not changed,
> which introduced bogus behavior: 32-bit application which mmaps
> file on hugetlbfs uses mm->mmap_base and thou tries to allocate
> space with 64-bit mmap() base.
> Changed x86 hugetlbfs code to use two bases according to calling
> syscall, which also will fix any problems with 32-bit syscalls
> in 64-bit ELF and vice-versa.
>
> Fixes: commit 1b028f784e8c ("x86/mm: Introduce mmap_compat_base() for
> 32-bit mmap()").
> Reported-by: kernel test robot <xiaolong.ye@intel.com>
> Cc: 0x7f454c46@gmail.com
> Cc: Cyrill Gorcunov <gorcunov@openvz.org>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
> Cc: H. Peter Anvin <hpa@zytor.com>
> Cc: linux-mm@kvack.org
> Cc: Andy Lutomirski <luto@kernel.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: x86@kernel.org
> Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
> ---
> Note: I've tested it on a simple hand-written test, will reply when
> got libhugetlbfs tests running in my environment.

Can confirm: I've tested this on clean fedora-25 with libhugetlbfs
tests, it's fixed.
Sorry for the breaking.

>
>  arch/x86/include/asm/elf.h   |  1 +
>  arch/x86/kernel/sys_x86_64.c | 12 ------------
>  arch/x86/mm/hugetlbpage.c    |  9 ++++++---
>  arch/x86/mm/mmap.c           | 13 +++++++++++++
>  4 files changed, 20 insertions(+), 15 deletions(-)
>
> diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
> index ac5be5ba8527..d4d3ed456cb7 100644
> --- a/arch/x86/include/asm/elf.h
> +++ b/arch/x86/include/asm/elf.h
> @@ -305,6 +305,7 @@ static inline int mmap_is_ia32(void)
>
>  extern unsigned long tasksize_32bit(void);
>  extern unsigned long tasksize_64bit(void);
> +extern unsigned long get_mmap_base(int is_legacy);
>
>  #ifdef CONFIG_X86_32
>
> diff --git a/arch/x86/kernel/sys_x86_64.c b/arch/x86/kernel/sys_x86_64.c
> index 63e89dfc808a..207b8f2582c7 100644
> --- a/arch/x86/kernel/sys_x86_64.c
> +++ b/arch/x86/kernel/sys_x86_64.c
> @@ -100,18 +100,6 @@ SYSCALL_DEFINE6(mmap, unsigned long, addr, unsigned long, len,
>  	return error;
>  }
>
> -static unsigned long get_mmap_base(int is_legacy)
> -{
> -	struct mm_struct *mm = current->mm;
> -
> -#ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
> -	if (in_compat_syscall())
> -		return is_legacy ? mm->mmap_compat_legacy_base
> -				 : mm->mmap_compat_base;
> -#endif
> -	return is_legacy ? mm->mmap_legacy_base : mm->mmap_base;
> -}
> -
>  static void find_start_end(unsigned long flags, unsigned long *begin,
>  			   unsigned long *end)
>  {
> diff --git a/arch/x86/mm/hugetlbpage.c b/arch/x86/mm/hugetlbpage.c
> index c5066a260803..a50f4600a281 100644
> --- a/arch/x86/mm/hugetlbpage.c
> +++ b/arch/x86/mm/hugetlbpage.c
> @@ -16,6 +16,8 @@
>  #include <asm/tlb.h>
>  #include <asm/tlbflush.h>
>  #include <asm/pgalloc.h>
> +#include <asm/elf.h>
> +#include <asm/compat.h>
>
>  #if 0	/* This is just for testing */
>  struct page *
> @@ -82,8 +84,9 @@ static unsigned long hugetlb_get_unmapped_area_bottomup(struct file *file,
>
>  	info.flags = 0;
>  	info.length = len;
> -	info.low_limit = current->mm->mmap_legacy_base;
> -	info.high_limit = TASK_SIZE;
> +	info.low_limit = get_mmap_base(1);
> +	info.high_limit = in_compat_syscall() ?
> +		tasksize_32bit() : tasksize_64bit();
>  	info.align_mask = PAGE_MASK & ~huge_page_mask(h);
>  	info.align_offset = 0;
>  	return vm_unmapped_area(&info);
> @@ -100,7 +103,7 @@ static unsigned long hugetlb_get_unmapped_area_topdown(struct file *file,
>  	info.flags = VM_UNMAPPED_AREA_TOPDOWN;
>  	info.length = len;
>  	info.low_limit = PAGE_SIZE;
> -	info.high_limit = current->mm->mmap_base;
> +	info.high_limit = get_mmap_base(0);
>  	info.align_mask = PAGE_MASK & ~huge_page_mask(h);
>  	info.align_offset = 0;
>  	addr = vm_unmapped_area(&info);
> diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
> index 529ab79800af..0fbb5a71b826 100644
> --- a/arch/x86/mm/mmap.c
> +++ b/arch/x86/mm/mmap.c
> @@ -31,6 +31,7 @@
>  #include <linux/sched/signal.h>
>  #include <linux/sched/mm.h>
>  #include <asm/elf.h>
> +#include <asm/compat.h>
>
>  struct va_alignment __read_mostly va_align = {
>  	.flags = -1,
> @@ -153,6 +154,18 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
>  #endif
>  }
>
> +unsigned long get_mmap_base(int is_legacy)
> +{
> +	struct mm_struct *mm = current->mm;
> +
> +#ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
> +	if (in_compat_syscall())
> +		return is_legacy ? mm->mmap_compat_legacy_base
> +				 : mm->mmap_compat_base;
> +#endif
> +	return is_legacy ? mm->mmap_legacy_base : mm->mmap_base;
> +}
> +
>  const char *arch_vma_name(struct vm_area_struct *vma)
>  {
>  	if (vma->vm_flags & VM_MPX)
>


-- 
              Dmitry

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