The mseal implementation is still rather confusing, so tighten things up a
little.

The only user of do_mseal() outside of the system call is the MMAP_PAGE_ZERO
process personality - retain better control over how mseal is utilised by
providing mseal_mmap_page_zero() for this instead.

The comments are overly long and confusion, so cut them down so they're a lot
clearer.

Remove confusing mm_struct params (mseal can not be used on remote mm's) and
wrap the actual system call logic into the system call declaration.

---
v2:
* Added tags (thanks everyone!)
* Abstracted mm as per David.
* Renamed [__]mseal() to [__]mseal_range() as per Pedro.
* Moved to reverse xmas tree declarations.
* Tweaked commit message for 2/3.

v1:
https://patch.msgid.link/20260716-mseal-fixups-v1-0-3a9609bf041b@kernel.org

To: Andrew Morton <akpm@linux-foundation.org>
To: "Liam R. Howlett" <liam@infradead.org>
To: Vlastimil Babka <vbabka@kernel.org>
To: Jann Horn <jannh@google.com>
To: Pedro Falcato <pfalcato@suse.de>
To: Alexander Viro <viro@zeniv.linux.org.uk>
To: Christian Brauner <brauner@kernel.org>
To: Jan Kara <jack@suse.cz>
To: Kees Cook <kees@kernel.org>
To: David Hildenbrand <david@kernel.org>
To: Mike Rapoport <rppt@kernel.org>
To: Suren Baghdasaryan <surenb@google.com>
To: Michal Hocko <mhocko@suse.com>
Cc: ljs@kernel.org
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org

---
Lorenzo Stoakes (ARM) (3):
      mm/mseal: remove superfluous comments, fix confusion around mm
      mm/mseal: limit scope of mseal address zero to address zero
      mm/mseal: remove further superfluous comments, do_mseal()

 fs/binfmt_elf.c    |   7 +--
 include/linux/mm.h |   8 +--
 mm/mseal.c         | 160 ++++++++++++++++++-----------------------------------
 3 files changed, 58 insertions(+), 117 deletions(-)
---
base-commit: 59c684a9908d2e6f7a791f7f033eae57ec2b3a61
change-id: 20260716-mseal-fixups-131ad0939de2

Cheers,
-- 
Lorenzo Stoakes (ARM) <ljs@kernel.org>

On Fri, 17 Jul 2026 18:27:08 +0100 "Lorenzo Stoakes (ARM)" <ljs@kernel.org> wrote:

> 
> The mseal implementation is still rather confusing, so tighten things up a
> little.
> 
> The only user of do_mseal() outside of the system call is the MMAP_PAGE_ZERO
> process personality - retain better control over how mseal is utilised by
> providing mseal_mmap_page_zero() for this instead.
> 
> The comments are overly long and confusion, so cut them down so they're a lot
> clearer.
> 
> Remove confusing mm_struct params (mseal can not be used on remote mm's) and
> wrap the actual system call logic into the system call declaration.

Thanks, I've updated mm-new to this version.

> v2:
> * Added tags (thanks everyone!)
> * Abstracted mm as per David.
> * Renamed [__]mseal() to [__]mseal_range() as per Pedro.
> * Moved to reverse xmas tree declarations.
> * Tweaked commit message for 2/3.

Here's how v2 altered mm.git:

 mm/mseal.c |   16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

--- a/mm/mseal.c~b
+++ a/mm/mseal.c
@@ -18,9 +18,9 @@
 
 static bool range_contains_unmapped(unsigned long start, unsigned long end)
 {
-	struct vm_area_struct *vma;
-	unsigned long prev_end = start;
 	VMA_ITERATOR(vmi, current->mm, start);
+	unsigned long prev_end = start;
+	struct vm_area_struct *vma;
 
 	for_each_vma_range(vmi, vma, end) {
 		if (vma->vm_start > prev_end)
@@ -32,10 +32,10 @@ static bool range_contains_unmapped(unsi
 	return prev_end < end;
 }
 
-static int __mseal(unsigned long start, unsigned long end)
+static int __mseal_range(unsigned long start, unsigned long end)
 {
-	struct vm_area_struct *vma, *prev;
 	VMA_ITERATOR(vmi, current->mm, start);
+	struct vm_area_struct *vma, *prev;
 
 	/* We know there are no gaps so this will be non-NULL. */
 	vma = vma_iter_load(&vmi);
@@ -66,7 +66,7 @@ static int __mseal(unsigned long start,
 	return 0;
 }
 
-static int mseal(unsigned long start, unsigned long end)
+static int mseal_range(unsigned long start, unsigned long end)
 {
 	int err;
 
@@ -76,7 +76,7 @@ static int mseal(unsigned long start, un
 	if (range_contains_unmapped(start, end))
 		err = -ENOMEM;
 	else
-		err = __mseal(start, end);
+		err = __mseal_range(start, end);
 	mmap_write_unlock(current->mm);
 	return err;
 }
@@ -92,7 +92,7 @@ void mseal_mmap_page_zero(void)
 	if (WARN_ON_ONCE(!(current->personality & MMAP_PAGE_ZERO)))
 		return;
 
-	err = mseal(0, PAGE_SIZE);
+	err = mseal_range(0, PAGE_SIZE);
 	if (err)
 		pr_warn_ratelimited("pid=%d, couldn't seal address 0, ret=%d.\n",
 				    task_pid_nr(current), err);
@@ -139,5 +139,5 @@ SYSCALL_DEFINE3(mseal, unsigned long, st
 	if (end == start)
 		return 0;
 
-	return mseal(start, end);
+	return mseal_range(start, end);
 }
_