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drm/mcde: dsi: Fix invalid pointer dereference if panel cannot be found

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The "panel" pointer is not reset to NULL if of_drm_find_panel()
returns an error. Therefore we later assume that a panel was found,
and try to dereference the error pointer, resulting in:

    mcde-dsi a0351000.dsi: failed to find panel try bridge (4294966779)
    Unable to handle kernel paging request at virtual address fffffe03
    PC is at drm_panel_bridge_add.part.0+0x10/0x5c
    LR is at mcde_dsi_bind+0x120/0x464
    ...

Reset "panel" to NULL to avoid this problem.
Also change the format string of the error to %ld to print
the negative errors correctly. The crash above then becomes:

    mcde-dsi a0351000.dsi: failed to find panel try bridge (-517)
    mcde-dsi a0351000.dsi: no panel or bridge
    ...

Fixes: 5fc537bfd0 ("drm/mcde: Add new driver for ST-Ericsson MCDE")
Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20191118130252.170324-1-stephan@gerhold.net
This commit is contained in:
Stephan Gerhold 2019-11-18 14:02:52 +01:00 committed by Linus Walleij
parent 0b8e7bbde5
commit c131280c03
1 changed files with 4 additions and 2 deletions
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6
drivers/gpu/drm/mcde/mcde_dsi.c
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@ -935,11 +935,13 @@ static int mcde_dsi_bind(struct device *dev, struct device *master,
for_each_available_child_of_node(dev->of_node, child) {
panel = of_drm_find_panel(child);
if (IS_ERR(panel)) {
dev_err(dev, "failed to find panel try bridge (%lu)\n",
dev_err(dev, "failed to find panel try bridge (%ld)\n",
PTR_ERR(panel));
panel = NULL;
bridge = of_drm_find_bridge(child);
if (IS_ERR(bridge)) {
dev_err(dev, "failed to find bridge (%lu)\n",
dev_err(dev, "failed to find bridge (%ld)\n",
PTR_ERR(bridge));
return PTR_ERR(bridge);
}