<[email protected]>,Catalin Marinas <[email protected]>,Mark Rutland <[email protected]>,James Morse <[email protected]>,linux-s390 <[email protected]>,LKML <[email protected]>,Linux API <[email protected]>,the arch/x86 maintainers <[email protected]>,[email protected],Kernel Hardening <[email protected]> From: [email protected] Message-ID: <[email protected]>
On April 4, 2017 12:21:48 PM PDT, Thomas Garnier <[email protected]> wrote: >On Tue, Apr 4, 2017 at 11:27 AM, H. Peter Anvin <[email protected]> wrote: >> On 04/04/17 10:47, Thomas Garnier wrote: >>> diff --git a/arch/x86/include/asm/pgtable_64_types.h >b/arch/x86/include/asm/pgtable_64_types.h >>> index 516593e66bd6..12fa851c7fa8 100644 >>> --- a/arch/x86/include/asm/pgtable_64_types.h >>> +++ b/arch/x86/include/asm/pgtable_64_types.h >>> @@ -78,4 +78,15 @@ typedef struct { pteval_t pte; } pte_t; >>> >>> #define EARLY_DYNAMIC_PAGE_TABLES 64 >>> >>> +/* >>> + * User space process size. 47bits minus one guard page. The guard >>> + * page is necessary on Intel CPUs: if a SYSCALL instruction is at >>> + * the highest possible canonical userspace address, then that >>> + * syscall will enter the kernel with a non-canonical return >>> + * address, and SYSRET will explode dangerously. We avoid this >>> + * particular problem by preventing anything from being mapped >>> + * at the maximum canonical address. >>> + */ >>> +#define TASK_SIZE_MAX ((_AC(1, UL) << 47) - PAGE_SIZE) >>> + >>> #endif /* _ASM_X86_PGTABLE_64_DEFS_H */ >>> diff --git a/arch/x86/include/asm/processor.h >b/arch/x86/include/asm/processor.h >>> index 3cada998a402..e80822582d3e 100644 >>> --- a/arch/x86/include/asm/processor.h >>> +++ b/arch/x86/include/asm/processor.h >>> @@ -825,17 +825,6 @@ static inline void spin_lock_prefetch(const >void *x) >>> #define KSTK_ESP(task) (task_pt_regs(task)->sp) >>> >>> #else >>> -/* >>> - * User space process size. 47bits minus one guard page. The guard >>> - * page is necessary on Intel CPUs: if a SYSCALL instruction is at >>> - * the highest possible canonical userspace address, then that >>> - * syscall will enter the kernel with a non-canonical return >>> - * address, and SYSRET will explode dangerously. We avoid this >>> - * particular problem by preventing anything from being mapped >>> - * at the maximum canonical address. >>> - */ >>> -#define TASK_SIZE_MAX ((1UL << 47) - PAGE_SIZE) >>> - >>> /* This decides where the kernel will search for a free chunk of vm >>> * space during mmap's. >>> */ >>> >> >> This should be an entirely separate patch; if nothing else you need >to >> explain it in the comments. > >I will explain it in the commit message, it should be easier than a >separate patch. > >> >> Also, you say this is for "x86", but I still don't see any code for >i386 >> whatsoever. Have you verified *all* the i386 and i386-compat paths >to >> make sure they go via prepare_exit_to_usermode()? [Cc: Andy] > >I did but I will do it again for the next iteration. > >> >> Finally, I can't really believe I'm the only person for whom >"Specific >> usage of verity_pre_usermode_state" is completely opaque. > >I agree, I will improve it. > >> >> -hpa >> Easier for you, perhaps, but not for everyone else... -- Sent from my Android device with K-9 Mail. Please excuse my brevity.
