linux-kernel - [PATCH 1/3] resource: Fix locking in find_next_iomem

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Message-Id: <20190613045903.4922-2-namit@vmware.com>
Date:   Wed, 12 Jun 2019 21:59:01 -0700
From:   Nadav Amit <namit@...are.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Nadav Amit <namit@...are.com>, stable@...r.kernel.org,
        Borislav Petkov <bp@...e.de>, Toshi Kani <toshi.kani@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Ingo Molnar <mingo@...nel.org>
Subject: [PATCH 1/3] resource: Fix locking in find_next_iomem_res()

Since resources can be removed, locking should ensure that the resource
is not removed while accessing it. However, find_next_iomem_res() does
not hold the lock while copying the data of the resource.

Keep holding the lock while the data is copied. While at it, change the
return value to a more informative value. It is disregarded by the
callers.

Fixes: ff3cc952d3f00 ("resource: Add remove_resource interface")
Cc: stable@...r.kernel.org
Cc: Borislav Petkov <bp@...e.de>
Cc: Toshi Kani <toshi.kani@....com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Nadav Amit <namit@...are.com>
---
 kernel/resource.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/kernel/resource.c b/kernel/resource.c
index 158f04ec1d4f..c0f7ba0ece52 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -365,16 +365,16 @@ static int find_next_iomem_res(resource_size_t start, resource_size_t end,
 			break;
 	}
 
+	if (p) {
+		/* copy data */
+		res->start = max(start, p->start);
+		res->end = min(end, p->end);
+		res->flags = p->flags;
+		res->desc = p->desc;
+	}
+
 	read_unlock(&resource_lock);
-	if (!p)
-		return -1;
-
-	/* copy data */
-	res->start = max(start, p->start);
-	res->end = min(end, p->end);
-	res->flags = p->flags;
-	res->desc = p->desc;
-	return 0;
+	return p ? 0 : -ENODEV;
 }
 
 static int __walk_iomem_res_desc(resource_size_t start, resource_size_t end,
-- 
2.20.1