linux-kernel - [PATCH 1/1] lib/ioremap.c: avoid endless loop under ioremapping page unaligned ranges

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Date:   Wed, 21 Sep 2016 12:19:53 +0800
From:   zijun_hu <zijun_hu@...o.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org, zijun_hu@....com,
        tj@...nel.org, mingo@...nel.org, rientjes@...gle.com,
        iamjoonsoo.kim@....com, mgorman@...hsingularity.net
Subject: [PATCH 1/1] lib/ioremap.c: avoid endless loop under ioremapping page
 unaligned ranges

From: zijun_hu <zijun_hu@....com>

endless loop maybe happen if either of parameter addr and end is not
page aligned for kernel API function ioremap_page_range()

in order to fix this issue and alert improper range parameters to user
WARN_ON() checkup and rounding down range lower boundary are performed
firstly, loop end condition within ioremap_pte_range() is optimized due
to lack of relevant macro pte_addr_end()

Signed-off-by: zijun_hu <zijun_hu@....com>
---
 lib/ioremap.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lib/ioremap.c b/lib/ioremap.c
index 86c8911..911bdca 100644
--- a/lib/ioremap.c
+++ b/lib/ioremap.c
@@ -64,7 +64,7 @@ static int ioremap_pte_range(pmd_t *pmd, unsigned long addr,
 		BUG_ON(!pte_none(*pte));
 		set_pte_at(&init_mm, addr, pte, pfn_pte(pfn, prot));
 		pfn++;
-	} while (pte++, addr += PAGE_SIZE, addr != end);
+	} while (pte++, addr += PAGE_SIZE, addr < end && addr >= PAGE_SIZE);
 	return 0;
 }
 
@@ -129,7 +129,9 @@ int ioremap_page_range(unsigned long addr,
 	int err;
 
 	BUG_ON(addr >= end);
+	WARN_ON(!PAGE_ALIGNED(addr) || !PAGE_ALIGNED(end));
 
+	addr = round_down(addr, PAGE_SIZE);
 	start = addr;
 	phys_addr -= addr;
 	pgd = pgd_offset_k(addr);
-- 
1.9.1