Currently MTE is permitted in two circumstances (desiring to use MTE having
been specified by the VM_MTE flag) - where MAP_ANONYMOUS is specified, as
checked by arch_calc_vm_flag_bits() and actualised by setting the
VM_MTE_ALLOWED flag, or if the file backing the mapping is shmem, in which
case we set VM_MTE_ALLOWED in shmem_mmap() when the mmap hook is activated
in mmap_region().
The function that checks that, if VM_MTE is set, VM_MTE_ALLOWED is also set
is the arm64 implementation of arch_validate_flags().
Unfortunately, we intend to refactor mmap_region() to perform this check
earlier, meaning that in the case of a shmem backing we will not have
invoked shmem_mmap() yet, causing the mapping to fail spuriously.
It is inappropriate to set this architecture-specific flag in general mm
code anyway, so a sensible resolution of this issue is to instead move the
check somewhere else.
We resolve this by setting VM_MTE_ALLOWED much earlier in do_mmap(), via
the arch_calc_vm_flag_bits() call.
This is an appropriate place to do this as we already check for the
MAP_ANONYMOUS case here, and the shmem file case is simply a variant of the
same idea - we permit RAM-backed memory.
This requires a modification to the arch_calc_vm_flag_bits() signature to
pass in a pointer to the struct file associated with the mapping, however
this is not too egregious as this is only used by two architectures anyway
- arm64 and parisc.
So this patch performs this adjustment and removes the unnecessary
assignment of VM_MTE_ALLOWED in shmem_mmap().
Suggested-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Reported-by: Jann Horn <jannh@xxxxxxxxxx>
Fixes: deb0f6562884 ("mm/mmap: undo ->mmap() when arch_validate_flags() fails")
Cc: stable <stable@xxxxxxxxxx>
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
---
arch/arm64/include/asm/mman.h | 10 +++++++---
arch/parisc/include/asm/mman.h | 5 +++--
include/linux/mman.h | 7 ++++---
mm/mmap.c | 2 +-
mm/nommu.c | 2 +-
mm/shmem.c | 3 ---
6 files changed, 16 insertions(+), 13 deletions(-)
diff --git a/arch/arm64/include/asm/mman.h b/arch/arm64/include/asm/mman.h
index 5966ee4a6154..ef35c52aabd6 100644
--- a/arch/arm64/include/asm/mman.h
+++ b/arch/arm64/include/asm/mman.h
@@ -3,6 +3,8 @@
#define __ASM_MMAN_H__
#include <linux/compiler.h>
+#include <linux/fs.h>
+#include <linux/shmem_fs.h>
#include <linux/types.h>
#include <uapi/asm/mman.h>
@@ -21,19 +23,21 @@ static inline unsigned long arch_calc_vm_prot_bits(unsigned long prot,
}
#define arch_calc_vm_prot_bits(prot, pkey) arch_calc_vm_prot_bits(prot, pkey)
-static inline unsigned long arch_calc_vm_flag_bits(unsigned long flags)
+static inline unsigned long arch_calc_vm_flag_bits(struct file *file,
+ unsigned long flags)
{
/*
* Only allow MTE on anonymous mappings as these are guaranteed to be
* backed by tags-capable memory. The vm_flags may be overridden by a
* filesystem supporting MTE (RAM-based).
*/
- if (system_supports_mte() && (flags & MAP_ANONYMOUS))
+ if (system_supports_mte() &&
+ ((flags & MAP_ANONYMOUS) || shmem_file(file)))
return VM_MTE_ALLOWED;
return 0;
}
-#define arch_calc_vm_flag_bits(flags) arch_calc_vm_flag_bits(flags)
+#define arch_calc_vm_flag_bits(file, flags) arch_calc_vm_flag_bits(file, flags)
static inline bool arch_validate_prot(unsigned long prot,
unsigned long addr __always_unused)
diff --git a/arch/parisc/include/asm/mman.h b/arch/parisc/include/asm/mman.h
index 89b6beeda0b8..663f587dc789 100644
--- a/arch/parisc/include/asm/mman.h
+++ b/arch/parisc/include/asm/mman.h
@@ -2,6 +2,7 @@
#ifndef __ASM_MMAN_H__
#define __ASM_MMAN_H__
+#include <linux/fs.h>
#include <uapi/asm/mman.h>
/* PARISC cannot allow mdwe as it needs writable stacks */
@@ -11,7 +12,7 @@ static inline bool arch_memory_deny_write_exec_supported(void)
}
#define arch_memory_deny_write_exec_supported arch_memory_deny_write_exec_supported
-static inline unsigned long arch_calc_vm_flag_bits(unsigned long flags)
+static inline unsigned long arch_calc_vm_flag_bits(struct file *file, unsigned long flags)
{
/*
* The stack on parisc grows upwards, so if userspace requests memory
@@ -23,6 +24,6 @@ static inline unsigned long arch_calc_vm_flag_bits(unsigned long flags)
return 0;
}
-#define arch_calc_vm_flag_bits(flags) arch_calc_vm_flag_bits(flags)
+#define arch_calc_vm_flag_bits(file, flags) arch_calc_vm_flag_bits(file, flags)
#endif /* __ASM_MMAN_H__ */
diff --git a/include/linux/mman.h b/include/linux/mman.h
index 651705c2bf47..b2e2677ea156 100644
--- a/include/linux/mman.h
+++ b/include/linux/mman.h
@@ -2,6 +2,7 @@
#ifndef _LINUX_MMAN_H
#define _LINUX_MMAN_H
+#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/percpu_counter.h>
@@ -94,7 +95,7 @@ static inline void vm_unacct_memory(long pages)
#endif
#ifndef arch_calc_vm_flag_bits
-#define arch_calc_vm_flag_bits(flags) 0
+#define arch_calc_vm_flag_bits(file, flags) 0
#endif
#ifndef arch_validate_prot
@@ -151,12 +152,12 @@ calc_vm_prot_bits(unsigned long prot, unsigned long pkey)
* Combine the mmap "flags" argument into "vm_flags" used internally.
*/
static inline unsigned long
-calc_vm_flag_bits(unsigned long flags)
+calc_vm_flag_bits(struct file *file, unsigned long flags)
{
return _calc_vm_trans(flags, MAP_GROWSDOWN, VM_GROWSDOWN ) |
_calc_vm_trans(flags, MAP_LOCKED, VM_LOCKED ) |
_calc_vm_trans(flags, MAP_SYNC, VM_SYNC ) |
- arch_calc_vm_flag_bits(flags);
+ arch_calc_vm_flag_bits(file, flags);
}
unsigned long vm_commit_limit(void);
diff --git a/mm/mmap.c b/mm/mmap.c
index d71ac65563b2..fca3429da2fe 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1273,7 +1273,7 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
* to. we assume access permissions have been handled by the open
* of the memory object, so we don't do any here.
*/
- vm_flags |= calc_vm_prot_bits(prot, pkey) | calc_vm_flag_bits(flags) |
+ vm_flags |= calc_vm_prot_bits(prot, pkey) | calc_vm_flag_bits(file, flags) |
mm->def_flags | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
if (flags & MAP_LOCKED)
diff --git a/mm/nommu.c b/mm/nommu.c
index 8bc339050e6d..7d37b734e66b 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -853,7 +853,7 @@ static unsigned long determine_vm_flags(struct file *file,
{
unsigned long vm_flags;
- vm_flags = calc_vm_prot_bits(prot, 0) | calc_vm_flag_bits(flags);
+ vm_flags = calc_vm_prot_bits(prot, 0) | calc_vm_flag_bits(file, flags);
if (!file) {
/*
diff --git a/mm/shmem.c b/mm/shmem.c
index 5d076022da24..78c061517a72 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2402,9 +2402,6 @@ static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
if (ret)
return ret;
- /* arm64 - allow memory tagging on RAM-based files */
- vm_flags_set(vma, VM_MTE_ALLOWED);
-
file_accessed(file);
/* This is anonymous shared memory if it is unlinked at the time of mmap */
if (inode->i_nlink)
--
2.47.0
