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Message-ID: <e67b7f6c682bddbea2fe8b2d87b8441e4d2ea6e6.1729628198.git.lorenzo.stoakes@oracle.com>
Date: Tue, 22 Oct 2024 21:40:54 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: "Liam R . Howlett" <Liam.Howlett@...cle.com>,
Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
Linus Torvalds <torvalds@...ux-foundation.org>,
Peter Xu <peterx@...hat.com>
Subject: [PATCH hotfix 6.12 3/8] mm: refactor map_deny_write_exec()
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.
Reported-by: Jann Horn <jannh@...gle.com>
Fixes: deb0f6562884 ("mm/mmap: undo ->mmap() when arch_validate_flags() fails")
Cc: stable <stable@...nel.org>
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
---
include/linux/mman.h | 21 ++++++++++++++++++---
mm/mmap.c | 2 +-
mm/mprotect.c | 2 +-
3 files changed, 20 insertions(+), 5 deletions(-)
diff --git a/include/linux/mman.h b/include/linux/mman.h
index bcb201ab7a41..d71f83b821ef 100644
--- a/include/linux/mman.h
+++ b/include/linux/mman.h
@@ -188,16 +188,31 @@ static inline bool arch_memory_deny_write_exec_supported(void)
*
* 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 absolutely do not accept writably executable... */
+ if (new & VM_WRITE)
return true;
- if (!(vma->vm_flags & VM_EXEC) && (vm_flags & VM_EXEC))
+ /* ...nor newly executable VMAs. */
+ if (!(old & VM_EXEC))
return true;
return false;
diff --git a/mm/mmap.c b/mm/mmap.c
index d55c58e99a54..66edf0ebba94 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1508,7 +1508,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
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;
}
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 0c5d6d06107d..6f450af3252e 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -810,7 +810,7 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
break;
}
- if (map_deny_write_exec(vma, newflags)) {
+ if (map_deny_write_exec(vma->vm_flags, newflags)) {
error = -EACCES;
break;
}
--
2.47.0
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