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 to arch_validate_flags() itself.
This requires a modification to the arch_validate_flags() 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 sparc.
So this patch performs this adjustment and moves the check to
arch_validate_flags() which resolves the issue.
We'd ideally like to have eliminated the arch_calc_vm_flag_bits() case, but
we risk inadvertently changing behaviour as we do not have mmap() flags
available at the point of the arch_validate_flags() check and a MAP_ANON |
MAP_HUGETLB case would be accepted for MTE currently, but a MAP_SHARED |
MAP_HUGETLB would not.
This is likely an oversight but we want to try to keep behaviour identical
to before in this patch.
So continue to check VM_MTE_ALLOWED which arch_calc_vm_flag_bits() sets if
MAP_ANON.
Reported-by: Jann Horn <jannh@xxxxxxxxxx>
Fixes: deb0f6562884 ("mm/mmap: undo ->mmap() when arch_validate_flags() fails")
Cc: stable <stable@xxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Tested-by: Mark Brown <broonie@xxxxxxxxxx>
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
---
arch/arm64/include/asm/mman.h | 29 +++++++++++++++++++++++++----
arch/sparc/include/asm/mman.h | 5 +++--
include/linux/mman.h | 2 +-
mm/mmap.c | 2 +-
mm/mprotect.c | 2 +-
mm/shmem.c | 3 ---
6 files changed, 31 insertions(+), 12 deletions(-)
diff --git a/arch/arm64/include/asm/mman.h b/arch/arm64/include/asm/mman.h
index 9e39217b4afb..94925a0482e3 100644
--- a/arch/arm64/include/asm/mman.h
+++ b/arch/arm64/include/asm/mman.h
@@ -6,7 +6,9 @@
#ifndef BUILD_VDSO
#include <linux/compiler.h>
+#include <linux/fs.h>
#include <linux/types.h>
+#include <linux/shmem_fs.h>
static inline unsigned long arch_calc_vm_prot_bits(unsigned long prot,
unsigned long pkey)
@@ -60,15 +62,34 @@ static inline bool arch_validate_prot(unsigned long prot,
}
#define arch_validate_prot(prot, addr) arch_validate_prot(prot, addr)
-static inline bool arch_validate_flags(unsigned long vm_flags)
+static inline bool arch_validate_flags(struct file *file, unsigned long vm_flags)
{
if (!system_supports_mte())
return true;
- /* only allow VM_MTE if VM_MTE_ALLOWED has been set previously */
- return !(vm_flags & VM_MTE) || (vm_flags & VM_MTE_ALLOWED);
+ if (!(vm_flags & VM_MTE))
+ return true;
+
+ /*
+ * We explicitly permit MAP_ANONYMOUS and shmem backed mappings to use
+ * MTE. We check for shmem explicitly here.
+ *
+ * The MAP_ANONYMOUS case is handled by arch_calc_vm_flag_bits() which
+ * explicitly sets VM_MTE_ALLOWED which we check for here also.
+ *
+ * Ideally we'd perform both checks here but existing semantics support
+ * hugetlb in MAP_ANONYMOUS mode but not a MAP_SHARED mapping, which is
+ * likely unintended but we maintain identical behaviour for
+ * consistency.
+ */
+ if (vm_flags & VM_MTE_ALLOWED)
+ return true;
+ if (shmem_file(file))
+ return true;
+
+ return false;
}
-#define arch_validate_flags(vm_flags) arch_validate_flags(vm_flags)
+#define arch_validate_flags(file, vm_flags) arch_validate_flags(file, vm_flags)
#endif /* !BUILD_VDSO */
diff --git a/arch/sparc/include/asm/mman.h b/arch/sparc/include/asm/mman.h
index af9c10c83dc5..d426e1f7c2c1 100644
--- a/arch/sparc/include/asm/mman.h
+++ b/arch/sparc/include/asm/mman.h
@@ -10,6 +10,7 @@ int sparc_mmap_check(unsigned long addr, unsigned long len);
#ifdef CONFIG_SPARC64
#include <asm/adi_64.h>
+#include <linux/fs.h>
static inline void ipi_set_tstate_mcde(void *arg)
{
@@ -54,11 +55,11 @@ static inline int sparc_validate_prot(unsigned long prot, unsigned long addr)
return 1;
}
-#define arch_validate_flags(vm_flags) arch_validate_flags(vm_flags)
+#define arch_validate_flags(file, vm_flags) arch_validate_flags(file, vm_flags)
/* arch_validate_flags() - Ensure combination of flags is valid for a
* VMA.
*/
-static inline bool arch_validate_flags(unsigned long vm_flags)
+static inline bool arch_validate_flags(struct file *file, unsigned long vm_flags)
{
/* If ADI is being enabled on this VMA, check for ADI
* capability on the platform and ensure VMA is suitable
diff --git a/include/linux/mman.h b/include/linux/mman.h
index 8ddca62d6460..82e6488026b7 100644
--- a/include/linux/mman.h
+++ b/include/linux/mman.h
@@ -117,7 +117,7 @@ static inline bool arch_validate_prot(unsigned long prot, unsigned long addr)
*
* Returns true if the VM_* flags are valid.
*/
-static inline bool arch_validate_flags(unsigned long flags)
+static inline bool arch_validate_flags(struct file *file, unsigned long flags)
{
return true;
}
diff --git a/mm/mmap.c b/mm/mmap.c
index ab71d4c3464c..40b5858ae875 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1511,7 +1511,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
}
/* Allow architectures to sanity-check the vm_flags */
- if (!arch_validate_flags(vma->vm_flags)) {
+ if (!arch_validate_flags(file, vma->vm_flags)) {
error = -EINVAL;
goto close_and_free_vma;
}
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 6f450af3252e..c6db98b893fc 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -816,7 +816,7 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
}
/* Allow architectures to sanity-check the new flags */
- if (!arch_validate_flags(newflags)) {
+ if (!arch_validate_flags(vma->vm_file, newflags)) {
error = -EINVAL;
break;
}
diff --git a/mm/shmem.c b/mm/shmem.c
index 4ba1d00fabda..e87f5d6799a7 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -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)
--
2.47.0
