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@xxxxxxxxx>
---
arch/x86/include/uapi/asm/resource.h | 5 +++++
arch/x86/kernel/cet.c | 10 ++++++++--
include/uapi/asm-generic/resource.h | 3 +++
mm/mmap.c | 12 +++++++++++-
4 files changed, 27 insertions(+), 3 deletions(-)
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/arch/x86/kernel/cet.c b/arch/x86/kernel/cet.c
index 071b9dd5bc5c..f700743f6f48 100644
--- a/arch/x86/kernel/cet.c
+++ b/arch/x86/kernel/cet.c
@@ -295,20 +295,26 @@ int cet_setup_ibt(void)
if (!cpu_feature_enabled(X86_FEATURE_IBT))
return -EOPNOTSUPP;
+ /*
+ * Calculate size and put in thread header.
+ * may_expand_vm() needs this information.
+ */
size = TASK_SIZE / PAGE_SIZE / BITS_PER_BYTE;
+ current->thread.cet.ibt_bitmap_size = size;
bitmap = do_mmap_locked(0, size, PROT_READ | PROT_WRITE,
MAP_ANONYMOUS | MAP_PRIVATE,
VM_DONTDUMP);
- if (bitmap >= TASK_SIZE)
+ if (bitmap >= TASK_SIZE) {
+ current->thread.cet.ibt_bitmap_size = 0;
return -ENOMEM;
+ }
rdmsrl(MSR_IA32_U_CET, r);
r |= (MSR_IA32_CET_ENDBR_EN | MSR_IA32_CET_NO_TRACK_EN);
wrmsrl(MSR_IA32_U_CET, r);
current->thread.cet.ibt_bitmap_addr = bitmap;
- current->thread.cet.ibt_bitmap_size = size;
current->thread.cet.ibt_enabled = 1;
return 0;
}
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 5f2b2b184c60..6f6c722c1484 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -3228,7 +3228,17 @@ 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) &&
--
2.17.1
