From: Rick Edgecombe <rick.p.edgecombe@intel.com>
Date: Tue, 26 Mar 2024 02:16:47 +0000 (-0700)
Subject: mm: use get_unmapped_area_vmflags()
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=8a0fe564bb2e744f21ca94e3eabe96d232cf5f41;p=linux.git
mm: use get_unmapped_area_vmflags()
When memory is being placed, mmap() will take care to respect the guard
gaps of certain types of memory (VM_SHADOWSTACK, VM_GROWSUP and
VM_GROWSDOWN). In order to ensure guard gaps between mappings, mmap()
needs to consider two things:
1. That the new mapping isn't placed in an any existing mappings guard
gaps.
2. That the new mapping isn't placed such that any existing mappings
are not in *its* guard gaps.
The long standing behavior of mmap() is to ensure 1, but not take any care
around 2. So for example, if there is a PAGE_SIZE free area, and a mmap()
with a PAGE_SIZE size, and a type that has a guard gap is being placed,
mmap() may place the shadow stack in the PAGE_SIZE free area. Then the
mapping that is supposed to have a guard gap will not have a gap to the
adjacent VMA.
Use mm_get_unmapped_area_vmflags() in the do_mmap() so future changes can
cause shadow stack mappings to be placed with a guard gap. Also use the
THP variant that takes vm_flags, such that THP shadow stack can get the
same treatment. Adjust the vm_flags calculation to happen earlier so that
the vm_flags can be passed into __get_unmapped_area().
Link: https://lkml.kernel.org/r/20240326021656.202649-6-rick.p.edgecombe@intel.com
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Aneesh Kumar K.V <aneesh.kumar@kernel.org>
Cc: Borislav Petkov (AMD) <bp@alien8.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Deepak Gupta <debug@rivosinc.com>
Cc: Guo Ren <guoren@kernel.org>
Cc: Helge Deller <deller@gmx.de>
Cc: H. Peter Anvin (Intel) <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Naveen N. Rao <naveen.n.rao@linux.ibm.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 3dda0dbcae144..1b6903f4c57b4 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3413,7 +3413,16 @@ extern int install_special_mapping(struct mm_struct *mm,
unsigned long randomize_stack_top(unsigned long stack_top);
unsigned long randomize_page(unsigned long start, unsigned long range);
-extern unsigned long get_unmapped_area(struct file *, unsigned long, unsigned long, unsigned long, unsigned long);
+unsigned long
+__get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
+ unsigned long pgoff, unsigned long flags, vm_flags_t vm_flags);
+
+static inline unsigned long
+get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
+ unsigned long pgoff, unsigned long flags)
+{
+ return __get_unmapped_area(file, addr, len, pgoff, flags, 0);
+}
extern unsigned long mmap_region(struct file *file, unsigned long addr,
unsigned long len, vm_flags_t vm_flags, unsigned long pgoff,
diff --git a/mm/mmap.c b/mm/mmap.c
index 30baba087c65e..a37c8dd29d64f 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1255,18 +1255,6 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
if (mm->map_count > sysctl_max_map_count)
return -ENOMEM;
- /* Obtain the address to map to. we verify (or select) it and ensure
- * that it represents a valid section of the address space.
- */
- addr = get_unmapped_area(file, addr, len, pgoff, flags);
- if (IS_ERR_VALUE(addr))
- return addr;
-
- if (flags & MAP_FIXED_NOREPLACE) {
- if (find_vma_intersection(mm, addr, addr + len))
- return -EEXIST;
- }
-
if (prot == PROT_EXEC) {
pkey = execute_only_pkey(mm);
if (pkey < 0)
@@ -1280,6 +1268,18 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
vm_flags |= calc_vm_prot_bits(prot, pkey) | calc_vm_flag_bits(flags) |
mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
+ /* Obtain the address to map to. we verify (or select) it and ensure
+ * that it represents a valid section of the address space.
+ */
+ addr = __get_unmapped_area(file, addr, len, pgoff, flags, vm_flags);
+ if (IS_ERR_VALUE(addr))
+ return addr;
+
+ if (flags & MAP_FIXED_NOREPLACE) {
+ if (find_vma_intersection(mm, addr, addr + len))
+ return -EEXIST;
+ }
+
if (flags & MAP_LOCKED)
if (!can_do_mlock())
return -EPERM;
@@ -1836,8 +1836,8 @@ unsigned long mm_get_unmapped_area_vmflags(struct mm_struct *mm, struct file *fi
}
unsigned long
-get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
- unsigned long pgoff, unsigned long flags)
+__get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
+ unsigned long pgoff, unsigned long flags, vm_flags_t vm_flags)
{
unsigned long (*get_area)(struct file *, unsigned long,
unsigned long, unsigned long, unsigned long)
@@ -1872,8 +1872,8 @@ get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
if (get_area)
addr = get_area(file, addr, len, pgoff, flags);
else
- addr = mm_get_unmapped_area(current->mm, file, addr, len,
- pgoff, flags);
+ addr = mm_get_unmapped_area_vmflags(current->mm, file, addr, len,
+ pgoff, flags, vm_flags);
if (IS_ERR_VALUE(addr))
return addr;