[PATCH v8 04/14] mm/mmap: Add IBT bitmap size to address space limit check

Yu-cheng Yu
2019-08-13T21:04:08Z

The indirect branch tracking legacy bitmap takes a large address
space. This causes may_expand_vm() failure on the address limit
check. For a IBT-enabled task, add the bitmap size to the
address limit.

Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
---
arch/x86/include/asm/mmu_context.h | 10 ++++++++++
mm/mmap.c | 19 ++++++++++++++++++-
2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index a9a768529540..e18e89ef332d 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -360,6 +360,16 @@ static inline unsigned long __get_current_cr3_fast(void)
return cr3;
}

+#ifdef CONFIG_X86_INTEL_BRANCH_TRACKING_USER
+static inline unsigned long arch_as_limit(void)
+{
+ if (current->thread.cet.ibt_enabled)
+ return IBT_BITMAP_SIZE;
+ else
+ return 0;
+}
+#endif
+
typedef struct {
struct mm_struct *mm;
} temp_mm_state_t;
diff --git a/mm/mmap.c b/mm/mmap.c
index 1acded00f003..1bfd9aec9aed 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -3283,13 +3283,30 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
return NULL;
}

+#ifndef CONFIG_ARCH_HAS_AS_LIMIT
+static inline unsigned long arch_as_limit(void)
+{
+ return 0;
+}
+#endif
+
/*
* Return true if the calling process may expand its vm space by the passed
* number of pages
*/
bool may_expand_vm(struct mm_struct *mm, vm_flags_t flags, unsigned long npages)
{
- if (mm->total_vm + npages > rlimit(RLIMIT_AS) >> PAGE_SHIFT)
+ unsigned long as_limit = rlimit(RLIMIT_AS);
+ unsigned long as_limit_plus = as_limit + arch_as_limit();
+
+ /* as_limit_plus overflowed */
+ if (as_limit_plus < as_limit)
+ as_limit_plus = RLIM_INFINITY;
+
+ if (as_limit_plus > as_limit)
+ as_limit = as_limit_plus;
+
+ if (mm->total_vm + npages > as_limit >> PAGE_SHIFT)
return false;

if (is_data_mapping(flags) &&
--
2.17.1