linux-kernel - [PATCH] x86/ioremap: tighten integer overflow checking

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Date:   Thu, 25 Oct 2018 09:16:33 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Dave Hansen <dave.hansen@...ux.intel.com>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH] x86/ioremap: tighten integer overflow checking

The current check is a bit off in the case where "phys_addr + size"
wraps to zero because then "last_addr" is set to ULONG_MAX which is >=
phys_addr.

Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
---
 arch/x86/mm/ioremap.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 5378d10f1d31..ee43df3ebe66 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -146,9 +146,9 @@ static void __iomem *__ioremap_caller(resource_size_t phys_addr,
 	void __iomem *ret_addr;
 
 	/* Don't allow wraparound or zero size */
-	last_addr = phys_addr + size - 1;
-	if (!size || last_addr < phys_addr)
+	if (!size || phys_addr + size < phys_addr)
 		return NULL;
+	last_addr = phys_addr + size - 1;
 
 	if (!phys_addr_valid(phys_addr)) {
 		printk(KERN_WARNING "ioremap: invalid physical address %llx\n",
-- 
2.11.0