FAILED: patch "[PATCH] mm/vma: fix expansion of VMA_MIXEDMAP_BIT VMAs" failed to apply to 7.3-stable tree

FAILED: patch "[PATCH] mm/vma: fix expansion of VMA_MIXEDMAP_BIT VMAs" failed to apply to 7.3-stable tree

[Sasha Levin]

The patch below does not apply to the 7.3-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-7.3.y
git checkout FETCH_HEAD
git cherry-pick -x 8146c6478224d8f6395c6b08a19c344a56d79867
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261109200136-failed-7.3-8146c6478224@kernel.org' --subject-prefix 'PATCH 7.3.y' 'HEAD^..'

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

From 8146c6478224d8f6395c6b08a19c344a56d79867 Mon Sep 17 00:00:00 2001
From: "Lorenzo Stoakes (ARM)" <ljs@kernel.org>
Date: Fri, 23 Oct 2026 16:17:31 +0100
Subject: [PATCH] mm/vma: fix expansion of VMA_MIXEDMAP_BIT VMAs
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Commit ca3d76b0aa80 ("mm: add merging after mremap resize") combined
merging with expansion of mremap()'d VMAs, however it also unintentionally
disallowed the expansion of unmergeable VMAs.

Previously it was possible to expand a mixed mapping which mremap() had
already ensured was a legal expansion.

This is clearly seen in the mremap() logic, as it checks
vma_is_fixed_mapping() to determine legality of an expansion rather than
vma_can_merge().

Additionally, copy_vma() allows for a failed merge to result in a new VMA
being instantiated if MREMAP_MAYMOVE is specified.

However, this is not attempted, as a failure in vma_merge_extend() is
assumed to be an -ENOMEM failure.

Since vma_merge_extend() is used exclusively by mremap() to perform a merge
and/or expansion, resolve the issue by invoking vma_expand() for
unmergeable VMAs there.

Explicitly assert that the VMA is both non-fixed and a mixed mapping.
This provides double insurance against broken changes in future.

Note that khugepaged_enter_vma() (which vma_merge_new_range() runs) is
redundant in this case, as a mixed mapping is not subject to khugepaged.

Also update the VMA userland tests to add a required predicate.

Link: https://lore.kernel.org/20261023-vma-expansion-fix-v1-1-6142baf1f46b@kernel.org
Fixes: ca3d76b0aa80 ("mm: add merging after mremap resize")
Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reported-by: Luiz Capitulino <luizcap@redhat.com>
Closes: https://lore.kernel.org/all/20261023023106.515365-1-luizcap@redhat.com/
Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Jann Horn <jannh@google.com>
Cc: Jakub Matěna <matenajakub@gmail.com>
Cc: <stable@vger.kernel.org>
---
 mm/vma.c                        | 19 ++++++++++++++++---
 tools/testing/vma/include/dup.h |  5 +++++
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/mm/vma.c b/mm/vma.c
index 1be613044b4a5..88ef92ab24ecf 100644
--- a/mm/vma.c
+++ b/mm/vma.c
@@ -1851,12 +1851,25 @@ struct vm_area_struct *vma_merge_extend(struct vma_iterator *vmi,
 					struct vm_area_struct *vma,
 					unsigned long delta)
 {
-	VMG_VMA_STATE(vmg, vmi, vma, vma, vma->vm_end, vma->vm_end + delta);
+	const unsigned long start =
+		vma_can_merge(vma) ? vma->vm_end : vma->vm_start;
+	VMG_VMA_STATE(vmg, vmi, vma, vma, start, vma->vm_end + delta);
 
-	vmg.next = vma_iter_next_rewind(vmi, NULL);
 	vmg.middle = NULL; /* We use the VMA to populate VMG fields only. */
 
-	return vma_merge_new_range(&vmg);
+	if (vma_can_merge(vma)) {
+		vmg.next = vma_iter_next_rewind(vmi, NULL);
+		return vma_merge_new_range(&vmg);
+	}
+
+	/* Mixed mappings are permitted to be expanded, not merged. */
+	VM_WARN_ON_ONCE(vma_is_fixed_mapping(vma));
+	VM_WARN_ON_ONCE(!vma_test(vma, VMA_MIXEDMAP_BIT));
+	vma_prev(vmi); /* Reposition to start of VMA. */
+	vmg.target = vma;
+	if (vma_expand(&vmg))
+		return NULL;
+	return vma;
 }
 
 void unlink_file_vma_batch_init(struct unlink_vma_file_batch *vb)
diff --git a/tools/testing/vma/include/dup.h b/tools/testing/vma/include/dup.h
index f449129ea97a9..e0eab4eca998e 100644
--- a/tools/testing/vma/include/dup.h
+++ b/tools/testing/vma/include/dup.h
@@ -1727,3 +1727,8 @@ static inline bool vma_flags_can_merge(const vma_flags_t *flags)
 	 */
 	return !vma_flags_is_hugetlb(flags);
 }
+
+static inline bool vma_can_merge(const struct vm_area_struct *vma)
+{
+	return vma_flags_can_merge(&vma->flags);
+}
-- 
2.53.0

[PATCH 7.3.y] mm/vma: fix expansion of VMA_MIXEDMAP_BIT VMAs

[Sasha Levin]

From: "Lorenzo Stoakes (ARM)" <ljs@kernel.org>

[ Upstream commit 8146c6478224d8f6395c6b08a19c344a56d79867 ]

Commit ca3d76b0aa80 ("mm: add merging after mremap resize") combined
merging with expansion of mremap()'d VMAs, however it also unintentionally
disallowed the expansion of unmergeable VMAs.

Previously it was possible to expand a mixed mapping which mremap() had
already ensured was a legal expansion.

This is clearly seen in the mremap() logic, as it checks
vma_is_fixed_mapping() to determine legality of an expansion rather than
vma_can_merge().

Additionally, copy_vma() allows for a failed merge to result in a new VMA
being instantiated if MREMAP_MAYMOVE is specified.

However, this is not attempted, as a failure in vma_merge_extend() is
assumed to be an -ENOMEM failure.

Since vma_merge_extend() is used exclusively by mremap() to perform a merge
and/or expansion, resolve the issue by invoking vma_expand() for
unmergeable VMAs there.

Explicitly assert that the VMA is both non-fixed and a mixed mapping.
This provides double insurance against broken changes in future.

Note that khugepaged_enter_vma() (which vma_merge_new_range() runs) is
redundant in this case, as a mixed mapping is not subject to khugepaged.

Also update the VMA userland tests to add a required predicate.

Link: https://lore.kernel.org/20261023-vma-expansion-fix-v1-1-6142baf1f46b@kernel.org
Fixes: ca3d76b0aa80 ("mm: add merging after mremap resize")
Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reported-by: Luiz Capitulino <luizcap@redhat.com>
Closes: https://lore.kernel.org/all/20261023023106.515365-1-luizcap@redhat.com/
Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Jann Horn <jannh@google.com>
Cc: Jakub Matěna <matenajakub@gmail.com>
Cc: <stable@vger.kernel.org>
[ sashal: Replaced vma_can_merge() and vma_is_fixed_mapping() with equivalent flag checks and is_vm_hugetlb_page(). ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 mm/vma.c | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/mm/vma.c b/mm/vma.c
index e382fd32f0fff..9863668b9d6bc 100644
--- a/mm/vma.c
+++ b/mm/vma.c
@@ -1882,12 +1882,28 @@ struct vm_area_struct *vma_merge_extend(struct vma_iterator *vmi,
 					struct vm_area_struct *vma,
 					unsigned long delta)
 {
-	VMG_VMA_STATE(vmg, vmi, vma, vma, vma->vm_end, vma->vm_end + delta);
+	const bool can_merge = !vma_test_any(vma, VMA_PFNMAP_BIT,
+					   VMA_DONTEXPAND_BIT, VMA_MIXEDMAP_BIT) &&
+			      !is_vm_hugetlb_page(vma);
+	const unsigned long start =
+		can_merge ? vma->vm_end : vma->vm_start;
+	VMG_VMA_STATE(vmg, vmi, vma, vma, start, vma->vm_end + delta);
 
-	vmg.next = vma_iter_next_rewind(vmi, NULL);
 	vmg.middle = NULL; /* We use the VMA to populate VMG fields only. */
 
-	return vma_merge_new_range(&vmg);
+	if (can_merge) {
+		vmg.next = vma_iter_next_rewind(vmi, NULL);
+		return vma_merge_new_range(&vmg);
+	}
+
+	/* Mixed mappings are permitted to be expanded, not merged. */
+	VM_WARN_ON_ONCE(vma_test_any(vma, VMA_PFNMAP_BIT, VMA_DONTEXPAND_BIT));
+	VM_WARN_ON_ONCE(!vma_test(vma, VMA_MIXEDMAP_BIT));
+	vma_prev(vmi); /* Reposition to start of VMA. */
+	vmg.target = vma;
+	if (vma_expand(&vmg))
+		return NULL;
+	return vma;
 }
 
 void unlink_file_vma_batch_init(struct unlink_vma_file_batch *vb)
-- 
2.53.0

Re: [PATCH 7.3.y] mm/vma: fix expansion of VMA_MIXEDMAP_BIT VMAs

[Luiz Capitulino]

On 11/11/26 10:10 PM, Sasha Levin wrote:
> From: "Lorenzo Stoakes (ARM)" <ljs@kernel.org>
> 
> [ Upstream commit 8146c6478224d8f6395c6b08a19c344a56d79867 ]
> 
> Commit ca3d76b0aa80 ("mm: add merging after mremap resize") combined
> merging with expansion of mremap()'d VMAs, however it also unintentionally
> disallowed the expansion of unmergeable VMAs.
> 
> Previously it was possible to expand a mixed mapping which mremap() had
> already ensured was a legal expansion.
> 
> This is clearly seen in the mremap() logic, as it checks
> vma_is_fixed_mapping() to determine legality of an expansion rather than
> vma_can_merge().
> 
> Additionally, copy_vma() allows for a failed merge to result in a new VMA
> being instantiated if MREMAP_MAYMOVE is specified.
> 
> However, this is not attempted, as a failure in vma_merge_extend() is
> assumed to be an -ENOMEM failure.
> 
> Since vma_merge_extend() is used exclusively by mremap() to perform a merge
> and/or expansion, resolve the issue by invoking vma_expand() for
> unmergeable VMAs there.
> 
> Explicitly assert that the VMA is both non-fixed and a mixed mapping.
> This provides double insurance against broken changes in future.
> 
> Note that khugepaged_enter_vma() (which vma_merge_new_range() runs) is
> redundant in this case, as a mixed mapping is not subject to khugepaged.
> 
> Also update the VMA userland tests to add a required predicate.
> 
> Link: https://lore.kernel.org/20261023-vma-expansion-fix-v1-1-6142baf1f46b@kernel.org
> Fixes: ca3d76b0aa80 ("mm: add merging after mremap resize")
> Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> Reported-by: Luiz Capitulino <luizcap@redhat.com>
> Closes: https://lore.kernel.org/all/20261023023106.515365-1-luizcap@redhat.com/
> Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
> Reviewed-by: Pedro Falcato <pfalcato@suse.de>
> Cc: Liam R. Howlett <liam@infradead.org>
> Cc: Jann Horn <jannh@google.com>
> Cc: Jakub Matěna <matenajakub@gmail.com>
> Cc: <stable@vger.kernel.org>
> [ sashal: Replaced vma_can_merge() and vma_is_fixed_mapping() with equivalent flag checks and is_vm_hugetlb_page(). ]
> Signed-off-by: Sasha Levin <sashal@kernel.org>

I tested this against the in-tree reproducer, ran the MM kselftests and
the vma selftest, all is good:

Tested-by: Luiz Capitulino <luizcap@redhat.com>

> ---
>   mm/vma.c | 22 +++++++++++++++++++---
>   1 file changed, 19 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/vma.c b/mm/vma.c
> index e382fd32f0fff..9863668b9d6bc 100644
> --- a/mm/vma.c
> +++ b/mm/vma.c
> @@ -1882,12 +1882,28 @@ struct vm_area_struct *vma_merge_extend(struct vma_iterator *vmi,
>   					struct vm_area_struct *vma,
>   					unsigned long delta)
>   {
> -	VMG_VMA_STATE(vmg, vmi, vma, vma, vma->vm_end, vma->vm_end + delta);
> +	const bool can_merge = !vma_test_any(vma, VMA_PFNMAP_BIT,
> +					   VMA_DONTEXPAND_BIT, VMA_MIXEDMAP_BIT) &&
> +			      !is_vm_hugetlb_page(vma);
> +	const unsigned long start =
> +		can_merge ? vma->vm_end : vma->vm_start;
> +	VMG_VMA_STATE(vmg, vmi, vma, vma, start, vma->vm_end + delta);
>   
> -	vmg.next = vma_iter_next_rewind(vmi, NULL);
>   	vmg.middle = NULL; /* We use the VMA to populate VMG fields only. */
>   
> -	return vma_merge_new_range(&vmg);
> +	if (can_merge) {
> +		vmg.next = vma_iter_next_rewind(vmi, NULL);
> +		return vma_merge_new_range(&vmg);
> +	}
> +
> +	/* Mixed mappings are permitted to be expanded, not merged. */
> +	VM_WARN_ON_ONCE(vma_test_any(vma, VMA_PFNMAP_BIT, VMA_DONTEXPAND_BIT));
> +	VM_WARN_ON_ONCE(!vma_test(vma, VMA_MIXEDMAP_BIT));
> +	vma_prev(vmi); /* Reposition to start of VMA. */
> +	vmg.target = vma;
> +	if (vma_expand(&vmg))
> +		return NULL;
> +	return vma;
>   }
>   
>   void unlink_file_vma_batch_init(struct unlink_vma_file_batch *vb)