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Subject[PATCH AUTOSEL 4.19 144/167] resource: fix locking in find_next_iomem_res()
Date
From: Nadav Amit <namit@vmware.com>

[ Upstream commit 49f17c26c123b60fd1c74629eef077740d16ffc2 ]

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.

[akpm@linux-foundation.org: fix find_next_iomem_res() documentation]
Link: http://lkml.kernel.org/r/20190613045903.4922-2-namit@vmware.com
Fixes: ff3cc952d3f00 ("resource: Add remove_resource interface")
Signed-off-by: Nadav Amit <namit@vmware.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: Toshi Kani <toshi.kani@hpe.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/resource.c | 20 ++++++++++----------
1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/kernel/resource.c b/kernel/resource.c
index 38b8d11c9eaf4..bce773cc5e416 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -325,7 +325,7 @@ EXPORT_SYMBOL(release_resource);
*
* If a resource is found, returns 0 and *res is overwritten with the part
* of the resource that's within [start..end]; if none is found, returns
- * -1.
+ * -ENODEV. Returns -EINVAL for invalid parameters.
*
* This function walks the whole tree and not just first level children
* unless @first_level_children_only is true.
@@ -359,16 +359,16 @@ 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
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