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    Subject[PATCH 4.19 164/190] resource: fix locking in find_next_iomem_res()
    Date
    [ 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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