Merge tag 'mm-stable-2024-05-24-11-49' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull more mm updates from Andrew Morton:
 "Jeff Xu's implementation of the mseal() syscall"

* tag 'mm-stable-2024-05-24-11-49' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm:
  selftest mm/mseal read-only elf memory segment
  mseal: add documentation
  selftest mm/mseal memory sealing
  mseal: add mseal syscall
  mseal: wire up mseal syscall

1 files changed, 30 insertions, 1 deletions

diff --git a/mm/mmap.c b/mm/mmap.c
index d6d8ab119b72..83b4682ec85c 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1255,6 +1255,16 @@ unsigned long do_mmap(struct file *file, unsigned long addr,
 	if (mm->map_count > sysctl_max_map_count)
 		return -ENOMEM;
 
+	/*
+	 * addr is returned from get_unmapped_area,
+	 * There are two cases:
+	 * 1> MAP_FIXED == false
+	 *	unallocated memory, no need to check sealing.
+	 * 1> MAP_FIXED == true
+	 *	sealing is checked inside mmap_region when
+	 *	do_vmi_munmap is called.
+	 */
+
 	if (prot == PROT_EXEC) {
 		pkey = execute_only_pkey(mm);
 		if (pkey < 0)
@@ -2727,6 +2737,14 @@ int do_vmi_munmap(struct vma_iterator *vmi, struct mm_struct *mm,
 	if (end == start)
 		return -EINVAL;
 
+	/*
+	 * Check if memory is sealed before arch_unmap.
+	 * Prevent unmapping a sealed VMA.
+	 * can_modify_mm assumes we have acquired the lock on MM.
+	 */
+	if (unlikely(!can_modify_mm(mm, start, end)))
+		return -EPERM;
+
 	 /* arch_unmap() might do unmaps itself.  */
 	arch_unmap(mm, start, end);
 
@@ -2789,7 +2807,10 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 	}
 
 	/* Unmap any existing mapping in the area */
-	if (do_vmi_munmap(&vmi, mm, addr, len, uf, false))
+	error = do_vmi_munmap(&vmi, mm, addr, len, uf, false);
+	if (error == -EPERM)
+		return error;
+	else if (error)
 		return -ENOMEM;
 
 	/*
@@ -3139,6 +3160,14 @@ int do_vma_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma,
 {
 	struct mm_struct *mm = vma->vm_mm;
 
+	/*
+	 * Check if memory is sealed before arch_unmap.
+	 * Prevent unmapping a sealed VMA.
+	 * can_modify_mm assumes we have acquired the lock on MM.
+	 */
+	if (unlikely(!can_modify_mm(mm, start, end)))
+		return -EPERM;
+
 	arch_unmap(mm, start, end);
 	return do_vmi_align_munmap(vmi, vma, mm, start, end, uf, unlock);
 }