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Subject[PATCH v5 04/11] mm/mmap: Add IBT bitmap size to address space limit check
Date
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 | 7 +++++++
mm/mmap.c | 19 ++++++++++++++++++-
2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index 8da7c999b7ee..9c726171e5c5 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -341,4 +341,11 @@ 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)
+{
+ return current->thread.cet.ibt_bitmap_size;
+}
+#endif
+
#endif /* _ASM_X86_MMU_CONTEXT_H */
diff --git a/mm/mmap.c b/mm/mmap.c
index fa581ced3f56..62b3045af005 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -3231,13 +3231,30 @@ struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
return NULL;
}

+#ifndef CONFIG_ARCH_HAS_AS_LIMIT
+static inline int 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
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