The patch titled
Subject: mm: refactor map_deny_write_exec()
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-refactor-map_deny_write_exec.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-refactor-map_deny_write_exec.patch
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@xxxxxxxxxx>
Subject: mm: refactor map_deny_write_exec()
Date: Wed, 23 Oct 2024 21:38:28 +0100
Refactor the map_deny_write_exec() to not unnecessarily require a VMA
parameter but rather to accept VMA flags parameters, which allows us to
use this function early in mmap_region() in a subsequent commit.
While we're here, we refactor the function to be more readable and add
some additional documentation.
Link: https://lkml.kernel.org/r/e82d23cebaa87fe5b767fecf9e730e0059066e63.1729715266.git.lorenzo.stoakes@xxxxxxxxxx
Fixes: deb0f6562884 ("mm/mmap: undo ->mmap() when arch_validate_flags() fails")
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
Reported-by: Jann Horn <jannh@xxxxxxxxxx>
Reviewed-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
Reviewed-by: Jann Horn <jannh@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/mman.h | 21 ++++++++++++++++++---
mm/mmap.c | 2 +-
mm/mprotect.c | 2 +-
mm/vma.h | 2 +-
4 files changed, 21 insertions(+), 6 deletions(-)
--- a/include/linux/mman.h~mm-refactor-map_deny_write_exec
+++ a/include/linux/mman.h
@@ -188,16 +188,31 @@ static inline bool arch_memory_deny_writ
*
* d) mmap(PROT_READ | PROT_EXEC)
* mmap(PROT_READ | PROT_EXEC | PROT_BTI)
+ *
+ * This is only applicable if the user has set the Memory-Deny-Write-Execute
+ * (MDWE) protection mask for the current process.
+ *
+ * @old specifies the VMA flags the VMA originally possessed, and @new the ones
+ * we propose to set.
+ *
+ * Return: false if proposed change is OK, true if not ok and should be denied.
*/
-static inline bool map_deny_write_exec(struct vm_area_struct *vma, unsigned long vm_flags)
+static inline bool map_deny_write_exec(unsigned long old, unsigned long new)
{
+ /* If MDWE is disabled, we have nothing to deny. */
if (!test_bit(MMF_HAS_MDWE, ¤t->mm->flags))
return false;
- if ((vm_flags & VM_EXEC) && (vm_flags & VM_WRITE))
+ /* If the new VMA is not executable, we have nothing to deny. */
+ if (!(new & VM_EXEC))
+ return false;
+
+ /* Under MDWE we do not accept newly writably executable VMAs... */
+ if (new & VM_WRITE)
return true;
- if (!(vma->vm_flags & VM_EXEC) && (vm_flags & VM_EXEC))
+ /* ...nor previously non-executable VMAs becoming executable. */
+ if (!(old & VM_EXEC))
return true;
return false;
--- a/mm/mmap.c~mm-refactor-map_deny_write_exec
+++ a/mm/mmap.c
@@ -1504,7 +1504,7 @@ unsigned long mmap_region(struct file *f
vma_set_anonymous(vma);
}
- if (map_deny_write_exec(vma, vma->vm_flags)) {
+ if (map_deny_write_exec(vma->vm_flags, vma->vm_flags)) {
error = -EACCES;
goto close_and_free_vma;
}
--- a/mm/mprotect.c~mm-refactor-map_deny_write_exec
+++ a/mm/mprotect.c
@@ -810,7 +810,7 @@ static int do_mprotect_pkey(unsigned lon
break;
}
- if (map_deny_write_exec(vma, newflags)) {
+ if (map_deny_write_exec(vma->vm_flags, newflags)) {
error = -EACCES;
break;
}
--- a/mm/vma.h~mm-refactor-map_deny_write_exec
+++ a/mm/vma.h
@@ -42,7 +42,7 @@ struct vma_munmap_struct {
int vma_count; /* Number of vmas that will be removed */
bool unlock; /* Unlock after the munmap */
bool clear_ptes; /* If there are outstanding PTE to be cleared */
- /* 1 byte hole */
+ /* 2 byte hole */
unsigned long nr_pages; /* Number of pages being removed */
unsigned long locked_vm; /* Number of locked pages */
unsigned long nr_accounted; /* Number of VM_ACCOUNT pages */
_
Patches currently in -mm which might be from lorenzo.stoakes@xxxxxxxxxx are
fork-do-not-invoke-uffd-on-fork-if-error-occurs.patch
fork-only-invoke-khugepaged-ksm-hooks-if-no-error.patch
mm-vma-add-expand-only-vma-merge-mode-and-optimise-do_brk_flags.patch
tools-testing-add-expand-only-mode-vma-test.patch
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-resolve-faulty-mmap_region-error-path-behaviour.patch
tools-testing-add-additional-vma_internalh-stubs.patch
mm-isolate-mmap-internal-logic-to-mm-vmac.patch
mm-refactor-__mmap_region.patch
mm-defer-second-attempt-at-merge-on-mmap.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
