linux-kernel - [PATCH 2/4] x86/mm/pat: Ensure that populate

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Date:   Tue,  3 Mar 2020 15:54:43 -0500
From:   Arvind Sankar <nivedita@...m.mit.edu>
To:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Ard Biesheuvel <ardb@...nel.org>, linux-efi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/4] x86/mm/pat: Ensure that populate_pud only handles one PUD

Add a check in populate_pgd to make sure that populate_pud is called on
a range that actually fits inside a PUD.

Signed-off-by: Arvind Sankar <nivedita@...m.mit.edu>
---
 arch/x86/mm/pat/set_memory.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index d0b7b06253a5..a1003bc9fdf6 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -1420,6 +1420,7 @@ static int populate_pgd(struct cpa_data *cpa, unsigned long addr)
 	p4d_t *p4d;
 	pgd_t *pgd_entry;
 	long ret;
+	unsigned long end, end_p4d;
 
 	pgd_entry = cpa->pgd + pgd_index(addr);
 
@@ -1443,6 +1444,15 @@ static int populate_pgd(struct cpa_data *cpa, unsigned long addr)
 		set_p4d(p4d, __p4d(__pa(pud) | _KERNPG_TABLE));
 	}
 
+	/*
+	 * Ensure that the range fits inside one p4d entry. If a larger range
+	 * was requested, __change_page_attr_set_clr will loop to finish it.
+	 */
+	end = addr + (cpa->numpages << PAGE_SHIFT);
+	end_p4d = (addr + P4D_SIZE) & P4D_MASK;
+	if (end_p4d < end)
+		cpa->numpages = (end_p4d - addr) >> PAGE_SHIFT;
+
 	pgprot_val(pgprot) &= ~pgprot_val(cpa->mask_clr);
 	pgprot_val(pgprot) |=  pgprot_val(cpa->mask_set);
 
-- 
2.24.1