Commit 0fb4a7ad authored by Lorenzo Stoakes's avatar Lorenzo Stoakes Committed by Andrew Morton
Browse files

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.

Link: https://lkml.kernel.org/r/6be8bb59cd7c68006ebb006eb9d8dc27104b1f70.1730224667.git.lorenzo.stoakes@oracle.com


Fixes: deb0f656 ("mm/mmap: undo ->mmap() when arch_validate_flags() fails")
Signed-off-by: default avatarLorenzo Stoakes <lorenzo.stoakes@oracle.com>
Reported-by: default avatarJann Horn <jannh@google.com>
Reviewed-by: default avatarLiam R. Howlett <Liam.Howlett@oracle.com>
Reviewed-by: default avatarVlastimil Babka <vbabka@suse.cz>
Reviewed-by: default avatarJann Horn <jannh@google.com>
Cc: Andreas Larsson <andreas@gaisler.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Helge Deller <deller@gmx.de>
Cc: James E.J. Bottomley <James.Bottomley@HansenPartnership.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: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 4080ef15

include/linux/mman.h

+18 −3
Original line number Diff line number Diff line
@@ -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, &current->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;

mm/mmap.c

+1 −1
Original line number Diff line number Diff line
@@ -1505,7 +1505,7 @@ 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;

	}

mm/mprotect.c

+1 −1
Original line number Diff line number Diff line
@@ -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;

		}

mm/vma.h

+1 −1
Original line number Diff line number Diff line
@@ -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 */