mm: refactor arch_calc_vm_flag_bits() and arm64 MTE handling

[ Upstream commit 5baf8b037debf4ec60108ccfeccb8636d1dbad81 ]

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>
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/include/asm/mman.h b/arch/arm64/include/asm/mman.h
index 5966ee4a61542edfa6ec513619adde639cead9b8..ef35c52aabd66dc2b10686b2b59e81ea12160239 100644 (file)
--- 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/include/linux/mman.h b/include/linux/mman.h
index 58b3abd457a38df455a870eca02cb0e63c6a3fc0..21ea08b919d9f20040393d5a0b33e0b35311070e 100644 (file)
--- 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>
 
@@ -90,7 +91,7 @@ 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
@@ -147,12 +148,12 @@ 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 4bfec4df51c2d0ba4a8fbfabdfcf5023e4e035a3..322677f61d30268d9c6c42b04ef6d1f7eeceb151 100644 (file)
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1316,7 +1316,7 @@ 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 e0428fa575269581c237adb2a0f4e3ce036f9a79..859ba6bdeb9ce3d5526d6c948412156417bdf9d0 100644 (file)
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -903,7 +903,7 @@ 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);
        /* vm_flags |= mm->def_flags; */
 
        if (!(capabilities & NOMMU_MAP_DIRECT)) {

diff --git a/mm/shmem.c b/mm/shmem.c
index f7c08e169e4230886ff20426a3eabdab40c0af91..2e6b7db7f14bdeb0b85fb12fb285f5a1f473e5e5 100644 (file)
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2306,9 +2306,6 @@ static int shmem_mmap(struct file *file, struct vm_area_struct *vma)
        if (ret)
                return ret;
 
-       /* arm64 - allow memory tagging on RAM-based files */
-       vma->vm_flags |= VM_MTE_ALLOWED;
-
        file_accessed(file);
        vma->vm_ops = &shmem_vm_ops;
        return 0;