FAILED: patch "[PATCH] arm64: Restrict pagetable teardown to avoid false warning" failed to apply to 5.15-stable tree

FAILED: patch "[PATCH] arm64: Restrict pagetable teardown to avoid false warning" failed to apply to 5.15-stable tree

[gregkh]

The patch below does not apply to the 5.15-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-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 650768c512faba8070bf4cfbb28c95eb5cd203f3
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2025062304-prune-getup-2943@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:



thanks,

greg k-h

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

From 650768c512faba8070bf4cfbb28c95eb5cd203f3 Mon Sep 17 00:00:00 2001
From: Dev Jain <dev.jain@arm.com>
Date: Tue, 27 May 2025 13:56:33 +0530
Subject: [PATCH] arm64: Restrict pagetable teardown to avoid false warning

Commit 9c006972c3fe ("arm64: mmu: drop pXd_present() checks from
pXd_free_pYd_table()") removes the pxd_present() checks because the
caller checks pxd_present(). But, in case of vmap_try_huge_pud(), the
caller only checks pud_present(); pud_free_pmd_page() recurses on each
pmd through pmd_free_pte_page(), wherein the pmd may be none. Thus it is
possible to hit a warning in the latter, since pmd_none => !pmd_table().
Thus, add a pmd_present() check in pud_free_pmd_page().

This problem was found by code inspection.

Fixes: 9c006972c3fe ("arm64: mmu: drop pXd_present() checks from pXd_free_pYd_table()")
Cc: stable@vger.kernel.org
Reported-by: Ryan Roberts <ryan.roberts@arm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Dev Jain <dev.jain@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Link: https://lore.kernel.org/r/20250527082633.61073-1-dev.jain@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 8fcf59ba39db..00ab1d648db6 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -1305,7 +1305,8 @@ int pud_free_pmd_page(pud_t *pudp, unsigned long addr)
 	next = addr;
 	end = addr + PUD_SIZE;
 	do {
-		pmd_free_pte_page(pmdp, next);
+		if (pmd_present(pmdp_get(pmdp)))
+			pmd_free_pte_page(pmdp, next);
 	} while (pmdp++, next += PMD_SIZE, next != end);
 
 	pud_clear(pudp);

[PATCH 5.15.y] arm64: Restrict pagetable teardown to avoid false warning

[Dev Jain]

[Commit 650768c512faba8070bf4cfbb28c95eb5cd203f3 upstream]

Commit 9c006972c3fe ("arm64: mmu: drop pXd_present() checks from
pXd_free_pYd_table()") removes the pxd_present() checks because the
caller checks pxd_present(). But, in case of vmap_try_huge_pud(), the
caller only checks pud_present(); pud_free_pmd_page() recurses on each
pmd through pmd_free_pte_page(), wherein the pmd may be none. Thus it is
possible to hit a warning in the latter, since pmd_none => !pmd_table().
Thus, add a pmd_present() check in pud_free_pmd_page().

This problem was found by code inspection.

Fixes: 9c006972c3fe ("arm64: mmu: drop pXd_present() checks from pXd_free_pYd_table()")
Cc: stable@vger.kernel.org
Reported-by: Ryan Roberts <ryan.roberts@arm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Dev Jain <dev.jain@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Link: https://lore.kernel.org/r/20250527082633.61073-1-dev.jain@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
(cherry picked from commit 650768c512faba8070bf4cfbb28c95eb5cd203f3)
(use READ_ONCE since pmdp_get() is not defined)
---
 arch/arm64/mm/mmu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index fc86e7465df4..e3e4defdea42 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -1466,7 +1466,8 @@ int pud_free_pmd_page(pud_t *pudp, unsigned long addr)
 	next = addr;
 	end = addr + PUD_SIZE;
 	do {
-		pmd_free_pte_page(pmdp, next);
+		if (pmd_present(READ_ONCE(*pmdp)))
+			pmd_free_pte_page(pmdp, next);
 	} while (pmdp++, next += PMD_SIZE, next != end);
 
 	pud_clear(pudp);
-- 
2.30.2

Re: [PATCH 5.15.y] arm64: Restrict pagetable teardown to avoid false warning

[Sasha Levin]

[ Sasha's backport helper bot ]

Hi,

✅ All tests passed successfully. No issues detected.
No action required from the submitter.

The upstream commit SHA1 provided is correct: 650768c512faba8070bf4cfbb28c95eb5cd203f3

Status in newer kernel trees:
6.15.y | Present (different SHA1: 1d03bbcb2b98)
6.12.y | Present (different SHA1: 47f34289d100)
6.6.y | Present (different SHA1: 6562806f3200)
6.1.y | Not found

Note: The patch differs from the upstream commit:
---
1:  650768c512fab ! 1:  fe24ec1815e3d arm64: Restrict pagetable teardown to avoid false warning
    @@ Metadata
      ## Commit message ##
         arm64: Restrict pagetable teardown to avoid false warning
     
    +    [Commit 650768c512faba8070bf4cfbb28c95eb5cd203f3 upstream]
    +
         Commit 9c006972c3fe ("arm64: mmu: drop pXd_present() checks from
         pXd_free_pYd_table()") removes the pxd_present() checks because the
         caller checks pxd_present(). But, in case of vmap_try_huge_pud(), the
    @@ Commit message
         Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
         Link: https://lore.kernel.org/r/20250527082633.61073-1-dev.jain@arm.com
         Signed-off-by: Will Deacon <will@kernel.org>
    +    (cherry picked from commit 650768c512faba8070bf4cfbb28c95eb5cd203f3)
    +    (use READ_ONCE since pmdp_get() is not defined)
     
      ## arch/arm64/mm/mmu.c ##
     @@ arch/arm64/mm/mmu.c: int pud_free_pmd_page(pud_t *pudp, unsigned long addr)
    @@ arch/arm64/mm/mmu.c: int pud_free_pmd_page(pud_t *pudp, unsigned long addr)
      	end = addr + PUD_SIZE;
      	do {
     -		pmd_free_pte_page(pmdp, next);
    -+		if (pmd_present(pmdp_get(pmdp)))
    ++		if (pmd_present(READ_ONCE(*pmdp)))
     +			pmd_free_pte_page(pmdp, next);
      	} while (pmdp++, next += PMD_SIZE, next != end);
      
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-5.15.y       |  Success    |  Success   |