[merged mm-stable] mm-prepare-lock_vma_under_rcu-for-vma-reuse-possibility.patch removed from -mm tree

[merged mm-stable] mm-prepare-lock_vma_under_rcu-for-vma-reuse-possibility.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: mm: prepare lock_vma_under_rcu() for vma reuse possibility
has been removed from the -mm tree.  Its filename was
     mm-prepare-lock_vma_under_rcu-for-vma-reuse-possibility.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Suren Baghdasaryan <surenb@google.com>
Subject: mm: prepare lock_vma_under_rcu() for vma reuse possibility
Date: Thu, 13 Feb 2025 14:46:53 -0800

Once we make vma cache SLAB_TYPESAFE_BY_RCU, it will be possible for a vma
to be reused and attached to another mm after lock_vma_under_rcu() locks
the vma.  lock_vma_under_rcu() should ensure that vma_start_read() is
using the original mm and after locking the vma it should ensure that
vma->vm_mm has not changed from under us.

Link: https://lkml.kernel.org/r/20250213224655.1680278-17-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Tested-by: Shivank Garg <shivankg@amd.com>
  Link: https://lkml.kernel.org/r/5e19ec93-8307-47c2-bb13-3ddf7150624e@amd.com
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Klara Modin <klarasmodin@gmail.com>
Cc: Liam R. Howlett <Liam.Howlett@Oracle.com>
Cc: Lokesh Gidra <lokeshgidra@google.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Mateusz Guzik <mjguzik@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: "Paul E . McKenney" <paulmck@kernel.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Sourav Panda <souravpanda@google.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Will Deacon <will@kernel.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/mm.h |   12 ++++++++----
 mm/memory.c        |    7 ++++---
 2 files changed, 12 insertions(+), 7 deletions(-)

--- a/include/linux/mm.h~mm-prepare-lock_vma_under_rcu-for-vma-reuse-possibility
+++ a/include/linux/mm.h
@@ -739,10 +739,13 @@ static inline void vma_refcount_put(stru
  * Try to read-lock a vma. The function is allowed to occasionally yield false
  * locked result to avoid performance overhead, in which case we fall back to
  * using mmap_lock. The function should never yield false unlocked result.
+ * False locked result is possible if mm_lock_seq overflows or if vma gets
+ * reused and attached to a different mm before we lock it.
  * Returns the vma on success, NULL on failure to lock and EAGAIN if vma got
  * detached.
  */
-static inline struct vm_area_struct *vma_start_read(struct vm_area_struct *vma)
+static inline struct vm_area_struct *vma_start_read(struct mm_struct *mm,
+						    struct vm_area_struct *vma)
 {
 	int oldcnt;
 
@@ -753,7 +756,7 @@ static inline struct vm_area_struct *vma
 	 * we don't rely on for anything - the mm_lock_seq read against which we
 	 * need ordering is below.
 	 */
-	if (READ_ONCE(vma->vm_lock_seq) == READ_ONCE(vma->vm_mm->mm_lock_seq.sequence))
+	if (READ_ONCE(vma->vm_lock_seq) == READ_ONCE(mm->mm_lock_seq.sequence))
 		return NULL;
 
 	/*
@@ -780,7 +783,7 @@ static inline struct vm_area_struct *vma
 	 * after it has been unlocked.
 	 * This pairs with RELEASE semantics in vma_end_write_all().
 	 */
-	if (unlikely(vma->vm_lock_seq == raw_read_seqcount(&vma->vm_mm->mm_lock_seq))) {
+	if (unlikely(vma->vm_lock_seq == raw_read_seqcount(&mm->mm_lock_seq))) {
 		vma_refcount_put(vma);
 		return NULL;
 	}
@@ -914,7 +917,8 @@ struct vm_area_struct *lock_vma_under_rc
 #else /* CONFIG_PER_VMA_LOCK */
 
 static inline void vma_lock_init(struct vm_area_struct *vma, bool reset_refcnt) {}
-static inline struct vm_area_struct *vma_start_read(struct vm_area_struct *vma)
+static inline struct vm_area_struct *vma_start_read(struct mm_struct *mm,
+						    struct vm_area_struct *vma)
 		{ return NULL; }
 static inline void vma_end_read(struct vm_area_struct *vma) {}
 static inline void vma_start_write(struct vm_area_struct *vma) {}
--- a/mm/memory.c~mm-prepare-lock_vma_under_rcu-for-vma-reuse-possibility
+++ a/mm/memory.c
@@ -6452,7 +6452,7 @@ retry:
 	if (!vma)
 		goto inval;
 
-	vma = vma_start_read(vma);
+	vma = vma_start_read(mm, vma);
 	if (IS_ERR_OR_NULL(vma)) {
 		/* Check if the VMA got isolated after we found it */
 		if (PTR_ERR(vma) == -EAGAIN) {
@@ -6471,8 +6471,9 @@ retry:
 	 * fields are accessible for RCU readers.
 	 */
 
-	/* Check since vm_start/vm_end might change before we lock the VMA */
-	if (unlikely(address < vma->vm_start || address >= vma->vm_end))
+	/* Check if the vma we locked is the right one. */
+	if (unlikely(vma->vm_mm != mm ||
+		     address < vma->vm_start || address >= vma->vm_end))
 		goto inval_end_read;
 
 	rcu_read_unlock();
_

Patches currently in -mm which might be from surenb@google.com are