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    Subject[PATCH 03/14] GPU-DRM-OMAP: Less function calls in tiler_map_show() after error detection
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    Date
    From: Markus Elfring <elfring@users.sourceforge.net>
    Date: Wed, 21 Sep 2016 13:16:20 +0200

    The kfree() function was called in up to two cases
    by the tiler_map_show() function during error handling even if
    the passed variable contained a null pointer.

    * Adjust jump targets according to the Linux coding style convention.

    * Split a condition check for memory allocation failures so that
    each pointer from these function calls will be checked immediately.

    See also background information:
    Topic "CWE-754: Improper check for unusual or exceptional conditions"
    Link: https://cwe.mitre.org/data/definitions/754.html

    * Return directly after a call of the function "kmalloc_array" failed
    at the beginning.

    * Move an assignment for the local variable "w_adj" behind the first
    memory allocation.

    Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
    ---
    drivers/gpu/drm/omapdrm/omap_dmm_tiler.c | 14 ++++++++------
    1 file changed, 8 insertions(+), 6 deletions(-)

    diff --git a/drivers/gpu/drm/omapdrm/omap_dmm_tiler.c b/drivers/gpu/drm/omapdrm/omap_dmm_tiler.c
    index 3a4f91b..60beeb9 100644
    --- a/drivers/gpu/drm/omapdrm/omap_dmm_tiler.c
    +++ b/drivers/gpu/drm/omapdrm/omap_dmm_tiler.c
    @@ -916,11 +916,14 @@ int tiler_map_show(struct seq_file *s, void *arg)
    }

    h_adj = omap_dmm->container_height / ydiv;
    - w_adj = omap_dmm->container_width / xdiv;
    map = kmalloc_array(h_adj, sizeof(*map), GFP_KERNEL);
    + if (!map)
    + return 0;
    +
    + w_adj = omap_dmm->container_width / xdiv;
    global_map = kmalloc_array(h_adj, w_adj + 1, GFP_KERNEL);
    - if (!map || !global_map)
    - goto error;
    + if (!global_map)
    + goto free_map;

    for (lut_idx = 0; lut_idx < omap_dmm->num_lut; lut_idx++) {
    memset(map, 0, h_adj * sizeof(*map));
    @@ -982,10 +985,9 @@ int tiler_map_show(struct seq_file *s, void *arg)
    }
    }

    -error:
    - kfree(map);
    kfree(global_map);
    -
    + free_map:
    + kfree(map);
    return 0;
    }
    #endif
    --
    2.10.0
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