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mm: refactor arch_calc_vm_flag_bits() and arm64 MTE handling

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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().

[akpm@linux-foundation.org: fix whitespace, per Catalin]
Link: https://lkml.kernel.org/r/ec251b20ba1964fb64cf1607d2ad80c47f3873df.1730224667.git.lorenzo.stoakes@oracle.com
Fixes: deb0f6562884 ("mm/mmap: undo ->mmap() when arch_validate_flags() fails")
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
Reported-by: Jann Horn <jannh@google.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Andreas Larsson <andreas@gaisler.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Helge Deller <deller@gmx.de>
Cc: James E.J. Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Will Deacon <will@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Lorenzo Stoakes 2024-10-29 18:11:47 +00:00 committed by Andrew Morton
parent 0fb4a7ad27
commit 5baf8b037d
6 changed files with 16 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
arch/arm64/include/asm/mman.h
View File

@ -6,6 +6,8 @@
#ifndef BUILD_VDSO
#include <linux/compiler.h>
#include <linux/fs.h>
#include <linux/shmem_fs.h>
#include <linux/types.h>
static inline unsigned long arch_calc_vm_prot_bits(unsigned long prot,
@ -31,19 +33,21 @@ 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)

5
arch/parisc/include/asm/mman.h
View File

@ -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__ */

7
include/linux/mman.h
View File

@ -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
@ -151,13 +152,13 @@ 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 ) |
_calc_vm_trans(flags, MAP_STACK, VM_NOHUGEPAGE) |
arch_calc_vm_flag_bits(flags);
arch_calc_vm_flag_bits(file, flags);
}
unsigned long vm_commit_limit(void);

2
mm/mmap.c
View File

@ -344,7 +344,7 @@ 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;
/* Obtain the address to map to. we verify (or select) it and ensure

2
mm/nommu.c
View File

@ -842,7 +842,7 @@ 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) {
/*

3
mm/shmem.c
View File

@ -2733,9 +2733,6 @@ 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)