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From:   Arvind Sankar <nivedita@alum.mit.edu>
To:     Ard Biesheuvel <ardb@kernel.org>, linux-efi@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org
Subject: [PATCH] efi/x86: Free efi_pgd with free_pages()
Date:   Tue, 10 Nov 2020 11:39:19 -0500
Message-Id: <20201110163919.1134431-1-nivedita@alum.mit.edu>
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Commit
  d9e9a6418065 ("x86/mm/pti: Allocate a separate user PGD")
changed the PGD allocation to allocate PGD_ALLOCATION_ORDER pages, so in
the error path it should be freed using free_pages() rather than
free_page().

Commit
  06ace26f4e6f ("x86/efi: Free efi_pgd with free_pages()")
fixed one instance of this, but missed another.

Move the freeing out-of-line to avoid code duplication and fix this bug.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Fixes: d9e9a6418065 ("x86/mm/pti: Allocate a separate user PGD")
---
 arch/x86/platform/efi/efi_64.c | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index 8f5759df7776..e1e8d4e3a213 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -78,28 +78,30 @@ int __init efi_alloc_page_tables(void)
 	gfp_mask = GFP_KERNEL | __GFP_ZERO;
 	efi_pgd = (pgd_t *)__get_free_pages(gfp_mask, PGD_ALLOCATION_ORDER);
 	if (!efi_pgd)
-		return -ENOMEM;
+		goto fail;
 
 	pgd = efi_pgd + pgd_index(EFI_VA_END);
 	p4d = p4d_alloc(&init_mm, pgd, EFI_VA_END);
-	if (!p4d) {
-		free_page((unsigned long)efi_pgd);
-		return -ENOMEM;
-	}
+	if (!p4d)
+		goto free_pgd;
 
 	pud = pud_alloc(&init_mm, p4d, EFI_VA_END);
-	if (!pud) {
-		if (pgtable_l5_enabled())
-			free_page((unsigned long) pgd_page_vaddr(*pgd));
-		free_pages((unsigned long)efi_pgd, PGD_ALLOCATION_ORDER);
-		return -ENOMEM;
-	}
+	if (!pud)
+		goto free_p4d;
 
 	efi_mm.pgd = efi_pgd;
 	mm_init_cpumask(&efi_mm);
 	init_new_context(NULL, &efi_mm);
 
 	return 0;
+
+free_p4d:
+	if (pgtable_l5_enabled())
+		free_page((unsigned long)pgd_page_vaddr(*pgd));
+free_pgd:
+	free_pages((unsigned long)efi_pgd, PGD_ALLOCATION_ORDER);
+fail:
+	return -ENOMEM;
 }
 
 /*
-- 
2.26.2