[PATCH 1/3] mm/mseal: remove superfluous comments, fix confusion around mm

[Lorenzo Stoakes (ARM)]

Remove comment blocks that don't add value and eliminate any confusion
about whether or not we permit mseal()'ing of remote mm's by explicitly
referencing current->mm consistently.

Also avoid ugly goto by using an else branch.

No functional change intended.

Signed-off-by: Lorenzo Stoakes (ARM) <ljs@xxxxxxxxxx>
---
 mm/mseal.c | 48 ++++++++----------------------------------------
 1 file changed, 8 insertions(+), 40 deletions(-)

diff --git a/mm/mseal.c b/mm/mseal.c
index 9781647483d1..207fea89c61e 100644
--- a/mm/mseal.c
+++ b/mm/mseal.c
@@ -16,28 +16,7 @@
 #include <linux/sched.h>
 #include "internal.h"
 
-/*
- * mseal() disallows an input range which contain unmapped ranges (VMA holes).
- *
- * It disallows unmapped regions from start to end whether they exist at the
- * start, in the middle, or at the end of the range, or any combination thereof.
- *
- * This is because after sealing a range, there's nothing to stop memory mapping
- * of ranges in the remaining gaps later, meaning that the user might then
- * wrongly consider the entirety of the mseal()'d range to be sealed when it
- * in fact isn't.
- */
-
-/*
- * Does the [start, end) range contain any unmapped memory?
- *
- * We ensure that:
- * - start is part of a valid VMA.
- * - end is part of a valid VMA.
- * - no gap (unallocated memory) exists between start and end.
- */
-static bool range_contains_unmapped(struct mm_struct *mm,
-		unsigned long start, unsigned long end)
+static bool range_contains_unmapped(unsigned long start, unsigned long end)
 {
 	struct vm_area_struct *vma;
 	unsigned long prev_end = start;
@@ -53,11 +32,10 @@ static bool range_contains_unmapped(struct mm_struct *mm,
 	return prev_end < end;
 }
 
-static int mseal_apply(struct mm_struct *mm,
-		unsigned long start, unsigned long end)
+static int mseal_apply(unsigned long start, unsigned long end)
 {
 	struct vm_area_struct *vma, *prev;
-	VMA_ITERATOR(vmi, mm, start);
+	VMA_ITERATOR(vmi, current->mm, start);
 
 	/* We know there are no gaps so this will be non-NULL. */
 	vma = vma_iter_load(&vmi);
@@ -145,7 +123,6 @@ int do_mseal(unsigned long start, size_t len_in, unsigned long flags)
 	size_t len;
 	int ret = 0;
 	unsigned long end;
-	struct mm_struct *mm = current->mm;
 
 	/* Verify flags not set. */
 	if (flags)
@@ -167,24 +144,15 @@ int do_mseal(unsigned long start, size_t len_in, unsigned long flags)
 	if (end == start)
 		return 0;
 
-	if (mmap_write_lock_killable(mm))
+	if (mmap_write_lock_killable(current->mm))
 		return -EINTR;
 
-	if (range_contains_unmapped(mm, start, end)) {
+	if (range_contains_unmapped(start, end))
 		ret = -ENOMEM;
-		goto out;
-	}
-
-	/*
-	 * Second pass, this should success, unless there are errors
-	 * from vma_modify_flags, e.g. merge/split error, or process
-	 * reaching the max supported VMAs, however, those cases shall
-	 * be rare.
-	 */
-	ret = mseal_apply(mm, start, end);
+	else
+		ret = mseal_apply(start, end);
 
-out:
-	mmap_write_unlock(mm);
+	mmap_write_unlock(current->mm);
 	return ret;
 }
 

-- 
2.55.0