4.14-stable review patch. If anyone has any objections, please let me know.
------------------
From: Andy Lutomirski luto@kernel.org
commit 49275fef986abfb8b476e4708aaecc07e7d3e087 upstream.
The kernel is very erratic as to which pagetables have _PAGE_USER set. The vsyscall page gets lucky: it seems that all of the relevant pagetables are among the apparently arbitrary ones that set _PAGE_USER. Rather than relying on chance, just explicitly set _PAGE_USER.
This will let us clean up pagetable setup to stop setting _PAGE_USER. The added code can also be reused by pagetable isolation to manage the _PAGE_USER bit in the usermode tables.
[ tglx: Folded paravirt fix from Juergen Gross ]
Signed-off-by: Andy Lutomirski luto@kernel.org Signed-off-by: Thomas Gleixner tglx@linutronix.de Cc: Borislav Petkov bp@alien8.de Cc: Brian Gerst brgerst@gmail.com Cc: Dave Hansen dave.hansen@linux.intel.com Cc: David Laight David.Laight@aculab.com Cc: H. Peter Anvin hpa@zytor.com Cc: Josh Poimboeuf jpoimboe@redhat.com Cc: Juergen Gross jgross@suse.com Cc: Kees Cook keescook@chromium.org Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/entry/vsyscall/vsyscall_64.c | 34 +++++++++++++++++++++++++++++++++- 1 file changed, 33 insertions(+), 1 deletion(-)
--- a/arch/x86/entry/vsyscall/vsyscall_64.c +++ b/arch/x86/entry/vsyscall/vsyscall_64.c @@ -37,6 +37,7 @@ #include <asm/unistd.h> #include <asm/fixmap.h> #include <asm/traps.h> +#include <asm/paravirt.h>
#define CREATE_TRACE_POINTS #include "vsyscall_trace.h" @@ -329,16 +330,47 @@ int in_gate_area_no_mm(unsigned long add return vsyscall_mode != NONE && (addr & PAGE_MASK) == VSYSCALL_ADDR; }
+/* + * The VSYSCALL page is the only user-accessible page in the kernel address + * range. Normally, the kernel page tables can have _PAGE_USER clear, but + * the tables covering VSYSCALL_ADDR need _PAGE_USER set if vsyscalls + * are enabled. + * + * Some day we may create a "minimal" vsyscall mode in which we emulate + * vsyscalls but leave the page not present. If so, we skip calling + * this. + */ +static void __init set_vsyscall_pgtable_user_bits(void) +{ + pgd_t *pgd; + p4d_t *p4d; + pud_t *pud; + pmd_t *pmd; + + pgd = pgd_offset_k(VSYSCALL_ADDR); + set_pgd(pgd, __pgd(pgd_val(*pgd) | _PAGE_USER)); + p4d = p4d_offset(pgd, VSYSCALL_ADDR); +#if CONFIG_PGTABLE_LEVELS >= 5 + p4d->p4d |= _PAGE_USER; +#endif + pud = pud_offset(p4d, VSYSCALL_ADDR); + set_pud(pud, __pud(pud_val(*pud) | _PAGE_USER)); + pmd = pmd_offset(pud, VSYSCALL_ADDR); + set_pmd(pmd, __pmd(pmd_val(*pmd) | _PAGE_USER)); +} + void __init map_vsyscall(void) { extern char __vsyscall_page; unsigned long physaddr_vsyscall = __pa_symbol(&__vsyscall_page);
- if (vsyscall_mode != NONE) + if (vsyscall_mode != NONE) { __set_fixmap(VSYSCALL_PAGE, physaddr_vsyscall, vsyscall_mode == NATIVE ? PAGE_KERNEL_VSYSCALL : PAGE_KERNEL_VVAR); + set_vsyscall_pgtable_user_bits(); + }
BUILD_BUG_ON((unsigned long)__fix_to_virt(VSYSCALL_PAGE) != (unsigned long)VSYSCALL_ADDR);