linux-kernel - [PATCH v5 2/6] x86/sev: Fix calculation of end address based on number of pages

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Date:   Tue, 27 Sep 2022 12:04:17 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     <linux-kernel@...r.kernel.org>, <x86@...nel.org>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        "H. Peter Anvin" <hpa@...or.com>,
        Michael Roth <michael.roth@....com>,
        Joerg Roedel <jroedel@...e.de>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH v5 2/6] x86/sev: Fix calculation of end address based on number of pages

When calculating an end address based on an unsigned int number of pages,
the number of pages must be cast to an unsigned long so that any value
greater than or equal to 0x100000 does not result in zero after the shift.

Fixes: dc3f3d2474b8 ("x86/mm: Validate memory when changing the C-bit")
Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
---
 arch/x86/kernel/sev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index cac56540929d..c90a47c39f6b 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -875,7 +875,7 @@ static void set_pages_state(unsigned long vaddr, unsigned int npages, int op)
 		panic("SNP: failed to allocate memory for PSC descriptor\n");
 
 	vaddr = vaddr & PAGE_MASK;
-	vaddr_end = vaddr + (npages << PAGE_SHIFT);
+	vaddr_end = vaddr + ((unsigned long)npages << PAGE_SHIFT);
 
 	while (vaddr < vaddr_end) {
 		/* Calculate the last vaddr that fits in one struct snp_psc_desc. */
-- 
2.37.3