diff mbox

[RFC,v2,23/27] mm/mmap: Add IBT bitmap size to address space limit check

Message ID 20180710222639.8241-24-yu-cheng.yu@intel.com (mailing list archive)
State New, archived
Headers show

Commit Message

Yu, Yu-cheng July 10, 2018, 10:26 p.m. UTC
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/uapi/asm/resource.h |  5 +++++
 include/uapi/asm-generic/resource.h  |  3 +++
 mm/mmap.c                            | 12 +++++++++++-
 3 files changed, 19 insertions(+), 1 deletion(-)

Comments

Dave Hansen July 10, 2018, 11:57 p.m. UTC | #1
On 07/10/2018 03:26 PM, Yu-cheng Yu wrote:
> 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.

This appears to require that we set up
current->thread.cet.ibt_bitmap_size _before_ calling may_expand_vm().
What keeps the ibt_mmap() itself from hitting the address limit?
Yu, Yu-cheng July 11, 2018, 4:56 p.m. UTC | #2
On Tue, 2018-07-10 at 16:57 -0700, Dave Hansen wrote:
> On 07/10/2018 03:26 PM, Yu-cheng Yu wrote:
> > 
> > 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.
> This appears to require that we set up
> current->thread.cet.ibt_bitmap_size _before_ calling may_expand_vm().
> What keeps the ibt_mmap() itself from hitting the address limit?

Yes, that is overlooked.  I will fix it.

Thanks,
Yu-cheng
diff mbox

Patch

diff --git a/arch/x86/include/uapi/asm/resource.h b/arch/x86/include/uapi/asm/resource.h
index 04bc4db8921b..0741b2a6101a 100644
--- a/arch/x86/include/uapi/asm/resource.h
+++ b/arch/x86/include/uapi/asm/resource.h
@@ -1 +1,6 @@ 
+/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
+#ifdef CONFIG_X86_INTEL_CET
+#define rlimit_as_extra() current->thread.cet.ibt_bitmap_size
+#endif
+
 #include <asm-generic/resource.h>
diff --git a/include/uapi/asm-generic/resource.h b/include/uapi/asm-generic/resource.h
index f12db7a0da64..8a7608a09700 100644
--- a/include/uapi/asm-generic/resource.h
+++ b/include/uapi/asm-generic/resource.h
@@ -58,5 +58,8 @@ 
 # define RLIM_INFINITY		(~0UL)
 #endif
 
+#ifndef rlimit_as_extra
+#define rlimit_as_extra() 0
+#endif
 
 #endif /* _UAPI_ASM_GENERIC_RESOURCE_H */
diff --git a/mm/mmap.c b/mm/mmap.c
index d1eb87ef4b1a..fad41b291ae1 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -3242,7 +3242,17 @@  struct vm_area_struct *copy_vma(struct vm_area_struct **vmap,
  */
 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 + rlimit_as_extra();
+
+	/* 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) &&