[merged mm-stable] mm-consistently-validate-vma-state-after-mmap-hooks.patch removed from -mm tree

[merged mm-stable] mm-consistently-validate-vma-state-after-mmap-hooks.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: mm: consistently validate VMA state after mmap[_prepare] hooks
has been removed from the -mm tree.  Its filename was
     mm-consistently-validate-vma-state-after-mmap-hooks.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: "Lorenzo Stoakes (ARM)" <ljs@kernel.org>
Subject: mm: consistently validate VMA state after mmap[_prepare] hooks
Date: Tue, 13 Oct 2026 16:04:43 +0100

When the f_op->mmap_prepare or deprecated f_op->mmap hooks are invoked, the
driver might have done something crazy that is not permitted by the kernel.

Currently we check for three such cases in __mmap_new_file_vma(), but only
if the legacy f_op->mmap hook is used:

* Did sparc ADI result in invalid flags?

* Did the driver alter vma->vm_start?

* Did the driver make a file-backed mapping on a read-only file writable?

Generalise these checks for both mmap_prepare and mmap and apply to all
invocations of mmap_file(), the f_op->mmap and f_op->mmap_prepare handling
in the core VMA code and the mmap_prepare compatibility layer.

Also extend the vm_start check to vm_end also - drivers must not change the
VMA range at all.

We also WARN_ON_ONCE() on these conditions as they are things that should
simply not occur in the kernel and it's important to call it out when it
does.

We invoke mmap_prepare_validate() after mmap_action_prepare(), as mmap
actions often manipulate state in the descriptor thus providing the final
state the VMA will be derived from.

Also call mmap_validate_vma_flags() in insert_vm_struct() to ensure that
special regions which are inserted (such as a VDSO or VVAR) also satisfy
the sanity checks.

This way every VMA established through an mmap hook, whether via mmap() or
the compatibility layer, or inserted via insert_vm_struct(), has been
validated. brk() VMAs never pass through a driver hook and so need no such
check.

While we're here, also fixup a couple disjoint blocks of #ifdef CONFIG_MMU.

Finally, update the VMA userland tests to reflect the change.

Link: https://lore.kernel.org/20261013-b4-mmap-prepare-vma-flag-sanify-v6-3-1aa3c9b139f9@kernel.org
Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Gregory Price (Meta) <gourry@gourry.net>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Jann Horn <jannh@google.com>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: David Hildenbrand <david@kernel.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Leon Romanovsky <leon@kernel.org>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Stephen Smalley <stephen.smalley.work@gmail.com>
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Takashi Iwai <tiwai@suse.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Eduard Zingerman <eddyz87@gmail.com>
Cc: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Nico Pache <nico.pache@linux.dev>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Usama Arif <usama.arif@linux.dev>
Cc: Kiryl Shutsemau <kas@kernel.org>
Cc: Doug Gilbert <dgilbert@interlog.com>
Cc: James Bottomley <james.bottomley@hansenpartnership.com>
Cc: Martin K. Petersen <mkp@kernel.org>
Cc: Simona Vetter <simona@ffwll.ch>
Cc: Helge Deller <deller@gmx.de>
Cc: Sebastian Reichel <sre@kernel.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Harry Yoo <harry@kernel.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Maxime Ripard <mripard@kernel.org>
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: David Airlie <airlied@gmail.com>
Cc: Will Deacon <will@kernel.org>
Cc: Aneesh Kumar K.V <aneesh.kumar@kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Oliver Upton <oupton@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Anup Patel <anup@brainfault.org>
Cc: Paul Walmsley <pjw@kernel.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Janosch Frank <frankja@linux.ibm.com>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Andreas Larsson <andreas@gaisler.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Matthew Brost <matthew.brost@intel.com>
Cc: Joshua Hahn <joshua.hahnjy@gmail.com>
Cc: Rakie Kim <rakie.kim@sk.com>
Cc: Byungchul Park <byungchul@sk.com>
Cc: Ying Huang <ying.huang@linux.alibaba.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Kairui Song <kasong@tencent.com>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Baoquan He <baoquan.he@linux.dev>
Cc: Youngjun Park <youngjun.park@lge.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Qi Zheng <qi.zheng@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Cc: Wei Xu <weixugc@google.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Xu Xin <xu.xin@linux.dev>
Cc: Ihor Solodrai <ihor.solodrai@linux.dev>
Cc: Bert Karwatzki <spasswolf@web.de>
---

 mm/internal.h                     |   50 ++++++++-----
 mm/util.c                         |   19 +++--
 mm/vma.c                          |  106 ++++++++++++++++++++++++----
 mm/vma.h                          |   25 +++++-
 tools/testing/vma/include/dup.h   |   10 ++
 tools/testing/vma/include/stubs.h |    4 +
 6 files changed, 172 insertions(+), 42 deletions(-)

--- a/mm/internal.h~mm-consistently-validate-vma-state-after-mmap-hooks
+++ a/mm/internal.h
@@ -214,6 +214,24 @@ static inline void *folio_raw_mapping(co
 }
 
 /*
+ * If the VMA has a close hook then close it, and since closing it might leave
+ * it in an inconsistent state which makes the use of any hooks suspect, clear
+ * them down by installing dummy empty hooks.
+ */
+static inline void vma_close(struct vm_area_struct *vma)
+{
+	if (vma->vm_ops && vma->vm_ops->close) {
+		vma->vm_ops->close(vma);
+
+		/*
+		 * The mapping is in an inconsistent state, and no further hooks
+		 * may be invoked upon it.
+		 */
+		vma->vm_ops = &vma_dummy_vm_ops;
+	}
+}
+
+/*
  * This is a file-backed mapping, and is about to be memory mapped - invoke its
  * mmap hook and safely handle error conditions. On error, VMA hooks will be
  * mutated.
@@ -225,8 +243,12 @@ static inline void *folio_raw_mapping(co
  */
 static inline int mmap_file(struct file *file, struct vm_area_struct *vma)
 {
-	int err = vfs_mmap(file, vma);
+	const unsigned long orig_start = vma->vm_start;
+	const unsigned long orig_end = vma->vm_end;
+	const vma_flags_t orig_flags = vma->flags;
+	int err;
 
+	err = vfs_mmap(file, vma);
 	/*
 	 * Either we tried to call the file hook for mmap() and an error arose
 	 * or a driver set vma->vm_ops = NULL intending there to be no VMA
@@ -239,26 +261,16 @@ static inline int mmap_file(struct file
 	 */
 	if (unlikely(err || !vma->vm_ops))
 		vma->vm_ops = &vma_dummy_vm_ops;
+	if (unlikely(err))
+		return err;
 
-	return err;
-}
-
-/*
- * If the VMA has a close hook then close it, and since closing it might leave
- * it in an inconsistent state which makes the use of any hooks suspect, clear
- * them down by installing dummy empty hooks.
- */
-static inline void vma_close(struct vm_area_struct *vma)
-{
-	if (vma->vm_ops && vma->vm_ops->close) {
-		vma->vm_ops->close(vma);
-
-		/*
-		 * The mapping is in an inconsistent state, and no further hooks
-		 * may be invoked upon it.
-		 */
-		vma->vm_ops = &vma_dummy_vm_ops;
+	err = mmap_hook_validate(orig_start, orig_end, &orig_flags, vma);
+	if (unlikely(err)) {
+		vma->vm_start = orig_start;
+		vma->vm_end = orig_end;
 	}
+
+	return err;
 }
 
 /* unmap_vmas is in mm/memory.c */
--- a/mm/util.c~mm-consistently-validate-vma-state-after-mmap-hooks
+++ a/mm/util.c
@@ -1224,19 +1224,28 @@ EXPORT_SYMBOL(compat_set_desc_from_vma);
 int __compat_vma_mmap(struct vm_area_desc *desc,
 		      struct vm_area_struct *vma)
 {
+	struct vm_area_desc orig_desc;
 	int err;
 
+	/* Derive state prior to mmap_prepare hook. */
+	compat_set_desc_from_vma(&orig_desc, desc->file, vma);
 	/* Perform any preparatory tasks for mmap action. */
 	err = mmap_action_prepare(desc);
-	if (err) {
-		if (desc->vm_file != vma->vm_file)
-			fput(desc->vm_file);
-		return err;
-	}
+	if (err)
+		goto err_put;
+	/* Check the caller did nothing crazy. */
+	err = mmap_prepare_validate(&orig_desc, desc);
+	if (err)
+		goto err_put;
 	/* Update the VMA from the descriptor. */
 	compat_set_vma_from_desc(vma, desc);
 	/* Complete any specified mmap actions. */
 	return mmap_action_complete(vma, &desc->action, /*is_compat=*/true);
+
+err_put:
+	if (desc->vm_file != vma->vm_file)
+		fput(desc->vm_file);
+	return err;
 }
 EXPORT_SYMBOL(__compat_vma_mmap);
 
--- a/mm/vma.c~mm-consistently-validate-vma-state-after-mmap-hooks
+++ a/mm/vma.c
@@ -2631,6 +2631,12 @@ static int __mmap_new_file_vma(struct mm
 	if (error) {
 		UNMAP_STATE(unmap, vmi, vma, vma->vm_start, vma->vm_end,
 			    map->prev, map->next);
+
+		if (vma->vm_ops->close) {
+			zap_vma(vma);
+			/* Safe, because VMA zapped. */
+			vma_close(vma);
+		}
 		if (map_same_file(map))
 			fput(map->vm_file);
 
@@ -2641,16 +2647,6 @@ static int __mmap_new_file_vma(struct mm
 		return error;
 	}
 
-	/* Drivers cannot alter the address of the VMA. */
-	WARN_ON_ONCE(map->addr != vma->vm_start);
-	/*
-	 * Drivers should not permit writability when previously it was
-	 * disallowed.
-	 */
-	VM_WARN_ON_ONCE(!vma_flags_same_pair(&map->vma_flags, &vma->flags) &&
-			!vma_flags_test(&map->vma_flags, VMA_MAYWRITE_BIT) &&
-			vma_test(vma, VMA_MAYWRITE_BIT));
-
 	map->vma_flags = vma->flags;
 
 	return 0;
@@ -2728,11 +2724,6 @@ static int __mmap_new_vma(struct mmap_st
 		vma->flags = map->vma_flags;
 	}
 
-#ifdef CONFIG_SPARC64
-	/* TODO: Fix SPARC ADI! */
-	WARN_ON_ONCE(!arch_validate_flags(map->vm_flags));
-#endif
-
 	/* Lock the VMA since it is modified after insertion into VMA tree */
 	vma_start_write(vma);
 	vma_iter_store_new(vmi, vma);
@@ -2795,6 +2786,80 @@ static void __mmap_complete(struct mmap_
 	vma_set_page_prot(vma);
 }
 
+/* Check to ensure that the VMA flags of a newly mapped VMA are sane. */
+static int mmap_validate_vma_flags(const vma_flags_t *flags)
+{
+#ifdef CONFIG_SPARC64
+	const vm_flags_t legacy_flags = vma_flags_to_legacy(*flags);
+
+	/* TODO: Fix SPARC ADI! */
+	if (WARN_ON_ONCE(!arch_validate_flags(legacy_flags)))
+		return -EINVAL;
+#endif
+
+	return 0;
+}
+
+/* Check to ensure a driver hasn't done something crazy. */
+static int mmap_validate(unsigned long orig_start, unsigned long orig_end,
+			 unsigned long curr_start, unsigned long curr_end,
+			 const vma_flags_t *orig_flags,
+			 const vma_flags_t *curr_flags)
+{
+	bool was_maywrite, is_maywrite;
+
+	/* Drivers cannot alter the range of the VMA. */
+	if (WARN_ON_ONCE(orig_start != curr_start || orig_end != curr_end))
+		return -EINVAL;
+
+	was_maywrite = vma_flags_test(orig_flags, VMA_MAYWRITE_BIT);
+	is_maywrite = vma_flags_test(curr_flags, VMA_MAYWRITE_BIT);
+
+	/* A driver may not make a previously unwritable mapping writable. */
+	if (WARN_ON_ONCE(!was_maywrite && is_maywrite))
+		return -EINVAL;
+
+	return mmap_validate_vma_flags(curr_flags);
+}
+
+/**
+ * mmap_prepare_validate() - Ensure the driver hasn't violated invariants in its
+ * f_op->mmap_prepare hook.
+ * @orig_desc: The VMA descriptor prior to the mmap_prepare hook being called.
+ * @desc: The VMA descriptor after the mmap_prepare hook has been called.
+ *
+ * Returns: 0 on success, otherwise an error.
+ */
+int mmap_prepare_validate(const struct vm_area_desc *orig_desc,
+			  const struct vm_area_desc *desc)
+{
+	return mmap_validate(orig_desc->start, orig_desc->end,
+			     desc->start, desc->end,
+			     &orig_desc->vma_flags, &desc->vma_flags);
+}
+
+/**
+ * mmap_hook_validate() - Ensure the driver hasn't violated invariants in
+ * its f_op->mmap hook.
+ * @orig_start: The start of the mapping prior to the mmap hook.
+ * @orig_end: The end of the mapping prior to the mmap hook.
+ * @orig_flags: The VMA flags set for the VMA prior to the mmap hook.
+ * @vma: The VMA after the hook has been applied.
+ *
+ * Returns: 0 on success, otherwise an error.
+ */
+int mmap_hook_validate(unsigned long orig_start, unsigned long orig_end,
+		       const vma_flags_t *orig_flags,
+		       const struct vm_area_struct *vma)
+{
+	const unsigned long start = vma->vm_start;
+	const unsigned long end = vma->vm_end;
+	const vma_flags_t *flags = &vma->flags;
+
+	return mmap_validate(orig_start, orig_end, start, end, orig_flags,
+			     flags);
+}
+
 static int call_action_prepare(struct mmap_state *map,
 			       struct vm_area_desc *desc)
 {
@@ -2821,6 +2886,7 @@ static int call_action_prepare(struct mm
 static int call_mmap_prepare(struct mmap_state *map,
 		struct vm_area_desc *desc)
 {
+	const struct vm_area_desc orig_desc = *desc;
 	int err;
 
 	/* Invoke the hook. */
@@ -2840,6 +2906,11 @@ static int call_mmap_prepare(struct mmap
 	if (err)
 		return err;
 
+	/* Check the caller did nothing crazy. */
+	err = mmap_prepare_validate(&orig_desc, desc);
+	if (err)
+		return err;
+
 	/* Update fields permitted to be changed. */
 	map->pgoff = desc->pgoff;
 	map->vma_flags = desc->vma_flags;
@@ -3475,10 +3546,15 @@ int __vm_munmap(unsigned long start, siz
 int insert_vm_struct(struct mm_struct *mm, struct vm_area_struct *vma)
 {
 	unsigned long charged = vma_pages(vma);
+	int err;
 
 	if (find_vma_intersection(mm, vma->vm_start, vma->vm_end))
 		return -ENOMEM;
 
+	err = mmap_validate_vma_flags(&vma->flags);
+	if (err)
+		return err;
+
 	if (vma_test(vma, VMA_ACCOUNT_BIT) &&
 	     security_vm_enough_memory_mm(mm, charged))
 		return -ENOMEM;
--- a/mm/vma.h~mm-consistently-validate-vma-state-after-mmap-hooks
+++ a/mm/vma.h
@@ -787,14 +787,19 @@ struct vm_area_struct *vm_area_alloc(str
 struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig);
 void vm_area_free(struct vm_area_struct *vma);
 
-/* vma_exec.c */
 #ifdef CONFIG_MMU
+int mmap_prepare_validate(const struct vm_area_desc *orig_desc,
+			  const struct vm_area_desc *desc);
+
+int mmap_hook_validate(unsigned long orig_start, unsigned long orig_end,
+		       const vma_flags_t *orig_flags,
+		       const struct vm_area_struct *vma);
+
+/* vma_exec.c */
 int create_init_stack_vma(struct mm_struct *mm, struct vm_area_struct **vmap,
 			  unsigned long *top_mem_p);
 int relocate_vma_down(struct vm_area_struct *vma, unsigned long shift);
-#endif
 
-#ifdef CONFIG_MMU
 /*
  * Denies creating a writable executable mapping or gaining executable permissions.
  *
@@ -843,6 +848,20 @@ static inline bool map_deny_write_exec(c
 
 	return false;
 }
+#else
+static inline int mmap_prepare_validate(const struct vm_area_desc *orig_desc,
+					const struct vm_area_desc *desc)
+{
+	return 0;
+}
+
+static inline int mmap_hook_validate(unsigned long orig_start,
+				     unsigned long orig_end,
+				     const vma_flags_t *orig_flags,
+				     const struct vm_area_struct *vma)
+{
+	return 0;
+}
 #endif
 
 struct vm_area_struct *__install_special_mapping(struct mm_struct *mm,
--- a/tools/testing/vma/include/dup.h~mm-consistently-validate-vma-state-after-mmap-hooks
+++ a/tools/testing/vma/include/dup.h
@@ -1359,15 +1359,25 @@ static inline int vfs_mmap_prepare(struc
 	return file->f_op->mmap_prepare(desc);
 }
 
+int mmap_prepare_validate(const struct vm_area_desc *orig_desc,
+			  const struct vm_area_desc *desc);
+
 static inline int __compat_vma_mmap(struct vm_area_desc *desc,
 		struct vm_area_struct *vma)
 {
+	struct vm_area_desc orig_desc;
 	int err;
 
+	/* Derive state prior to mmap_prepare hook. */
+	compat_set_desc_from_vma(&orig_desc, desc->file, vma);
 	/* Perform any preparatory tasks for mmap action. */
 	err = mmap_action_prepare(desc);
 	if (err)
 		return err;
+	/* Check the caller did nothing crazy. */
+	err = mmap_prepare_validate(&orig_desc, desc);
+	if (err)
+		return err;
 	/* Update the VMA from the descriptor. */
 	compat_set_vma_from_desc(vma, desc);
 	/* Complete any specified mmap actions. */
--- a/tools/testing/vma/include/stubs.h~mm-consistently-validate-vma-state-after-mmap-hooks
+++ a/tools/testing/vma/include/stubs.h
@@ -329,6 +329,10 @@ static inline void vma_close(struct vm_a
 {
 }
 
+static inline void zap_vma(struct vm_area_struct *vma)
+{
+}
+
 static inline int mmap_file(struct file *file, struct vm_area_struct *vma)
 {
 	return 0;
_

Patches currently in -mm which might be from ljs@kernel.org are

mm-vma-fix-expansion-of-vma_mixedmap_bit-vmas.patch
mm-do-not-unintentionally-overwrite-atomic-vma-flags.patch
mm-vma-avoid-losing-atomic-vma-flags-when-setting-sticky-vma-flags.patch