linux-kernel - [PATCH v4 10/21] mm/mmap: Support vma == NULL in init_vma

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Message-ID: <20240710192250.4114783-11-Liam.Howlett@oracle.com>
Date: Wed, 10 Jul 2024 15:22:39 -0400
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>
Cc: Suren Baghdasaryan <surenb@...gle.com>, Vlastimil Babka <vbabka@...e.cz>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        Matthew Wilcox <willy@...radead.org>, sidhartha.kumar@...cle.com,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Bert Karwatzki <spasswolf@....de>, Jiri Olsa <olsajiri@...il.com>,
        linux-kernel@...r.kernel.org, Kees Cook <kees@...nel.org>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>
Subject: [PATCH v4 10/21] mm/mmap: Support vma == NULL in init_vma_munmap()

From: "Liam R. Howlett" <Liam.Howlett@...cle.com>

Adding support for a NULL vma means the init_vma_munmap() can be
initialized for a less error-prone process when calling
vms_complete_munmap_vmas() later on.

Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
---
 mm/mmap.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/mm/mmap.c b/mm/mmap.c
index a1544a68558e..e2e6b3202c25 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -516,10 +516,12 @@ static inline void init_vma_munmap(struct vma_munmap_struct *vms,
 		bool unlock)
 {
 	vms->vmi = vmi;
-	vms->vma = vma;
-	vms->mm = vma->vm_mm;
-	vms->start = start;
-	vms->end = end;
+	if (vma) {
+		vms->vma = vma;
+		vms->mm = vma->vm_mm;
+		vms->start = start;
+		vms->end = end;
+	}
 	vms->unlock = unlock;
 	vms->uf = uf;
 	vms->vma_count = 0;
@@ -2950,11 +2952,11 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
 
 	/* Find the first overlapping VMA */
 	vma = vma_find(&vmi, end);
+	init_vma_munmap(&vms, &vmi, vma, addr, end, uf, /* unlock = */ false);
 	if (vma) {
 		mt_init_flags(&mt_detach, vmi.mas.tree->ma_flags & MT_FLAGS_LOCK_MASK);
 		mt_on_stack(mt_detach);
 		mas_init(&mas_detach, &mt_detach, /* addr = */ 0);
-		init_vma_munmap(&vms, &vmi, vma, addr, end, uf, /* unlock = */ false);
 		/* Prepare to unmap any existing mapping in the area */
 		if (vms_gather_munmap_vmas(&vms, &mas_detach))
 			return -ENOMEM;
-- 
2.43.0