The patch titled Subject: mm: refactor arch_calc_vm_flag_bits() and arm64 MTE handling has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-refactor-arch_calc_vm_flag_bits-and-arm64-mte-handling.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Lorenzo Stoakes lorenzo.stoakes@oracle.com Subject: mm: refactor arch_calc_vm_flag_bits() and arm64 MTE handling Date: Tue, 29 Oct 2024 18:11:47 +0000

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().

Link: https://lkml.kernel.org/r/ec251b20ba1964fb64cf1607d2ad80c47f3873df.173022466... 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 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: Vlastimil Babka vbabka@suse.cz Cc: Will Deacon will@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

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(-)

--- a/arch/arm64/include/asm/mman.h~mm-refactor-arch_calc_vm_flag_bits-and-arm64-mte-handling +++ a/arch/arm64/include/asm/mman.h @@ -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 } #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) --- a/arch/parisc/include/asm/mman.h~mm-refactor-arch_calc_vm_flag_bits-and-arm64-mte-handling +++ a/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_writ } #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

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__ */ --- a/include/linux/mman.h~mm-refactor-arch_calc_vm_flag_bits-and-arm64-mte-handling +++ a/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 #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, un * 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); --- a/mm/mmap.c~mm-refactor-arch_calc_vm_flag_bits-and-arm64-mte-handling +++ a/mm/mmap.c @@ -344,7 +344,7 @@ unsigned long do_mmap(struct file *file, * 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 --- a/mm/nommu.c~mm-refactor-arch_calc_vm_flag_bits-and-arm64-mte-handling +++ a/mm/nommu.c @@ -842,7 +842,7 @@ static unsigned long determine_vm_flags( { 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) { /* --- a/mm/shmem.c~mm-refactor-arch_calc_vm_flag_bits-and-arm64-mte-handling +++ a/mm/shmem.c @@ -2733,9 +2733,6 @@ static int shmem_mmap(struct file *file, 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) _

Patches currently in -mm which might be from lorenzo.stoakes@oracle.com are

mm-avoid-unsafe-vma-hook-invocation-when-error-arises-on-mmap-hook.patch mm-unconditionally-close-vmas-on-error.patch mm-refactor-map_deny_write_exec.patch mm-refactor-arch_calc_vm_flag_bits-and-arm64-mte-handling.patch mm-resolve-faulty-mmap_region-error-path-behaviour.patch selftests-mm-add-pkey_sighandler_xx-hugetlb_dio-to-gitignore.patch mm-refactor-mm_access-to-not-return-null.patch mm-refactor-mm_access-to-not-return-null-fix.patch mm-madvise-unrestrict-process_madvise-for-current-process.patch maple_tree-do-not-hash-pointers-on-dump-in-debug-mode.patch tools-testing-fix-phys_addr_t-size-on-64-bit-systems.patch tools-testing-fix-phys_addr_t-size-on-64-bit-systems-fix.patch tools-testing-add-additional-vma_internalh-stubs.patch mm-isolate-mmap-internal-logic-to-mm-vmac.patch mm-refactor-__mmap_region.patch mm-remove-unnecessary-reset-state-logic-on-merge-new-vma.patch mm-defer-second-attempt-at-merge-on-mmap.patch mm-defer-second-attempt-at-merge-on-mmap-fix.patch mm-pagewalk-add-the-ability-to-install-ptes.patch mm-add-pte_marker_guard-pte-marker.patch mm-madvise-implement-lightweight-guard-page-mechanism.patch tools-testing-update-tools-uapi-header-for-mman-commonh.patch selftests-mm-add-self-tests-for-guard-page-feature.patch