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    Subject[PATCH 5.3 099/105] RDMA/qib: Validate ->show()/store() callbacks before calling them
    Date
    From: Viresh Kumar <viresh.kumar@linaro.org>

    commit 7ee23491b39259ae83899dd93b2a29ef0f22f0a7 upstream.

    The permissions of the read-only or write-only sysfs files can be
    changed (as root) and the user can then try to read a write-only file or
    write to a read-only file which will lead to kernel crash here.

    Protect against that by always validating the show/store callbacks.

    Link: https://lore.kernel.org/r/d45cc26361a174ae12dbb86c994ef334d257924b.1573096807.git.viresh.kumar@linaro.org
    Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
    Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/infiniband/hw/qib/qib_sysfs.c | 6 ++++++
    1 file changed, 6 insertions(+)

    --- a/drivers/infiniband/hw/qib/qib_sysfs.c
    +++ b/drivers/infiniband/hw/qib/qib_sysfs.c
    @@ -301,6 +301,9 @@ static ssize_t qib_portattr_show(struct
    struct qib_pportdata *ppd =
    container_of(kobj, struct qib_pportdata, pport_kobj);

    + if (!pattr->show)
    + return -EIO;
    +
    return pattr->show(ppd, buf);
    }

    @@ -312,6 +315,9 @@ static ssize_t qib_portattr_store(struct
    struct qib_pportdata *ppd =
    container_of(kobj, struct qib_pportdata, pport_kobj);

    + if (!pattr->store)
    + return -EIO;
    +
    return pattr->store(ppd, buf, len);
    }


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