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    Subject[PATCH 6.0 378/862] drm/bridge: megachips: Fix a null pointer dereference bug
    Date
    From: Zheyu Ma <zheyuma97@gmail.com>

    [ Upstream commit 1ff673333d46d2c1b053ebd0c1c7c7c79e36943e ]

    When removing the module we will get the following warning:

    [ 31.911505] i2c-core: driver [stdp2690-ge-b850v3-fw] unregistered
    [ 31.912484] general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN PTI
    [ 31.913338] KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f]
    [ 31.915280] RIP: 0010:drm_bridge_remove+0x97/0x130
    [ 31.921825] Call Trace:
    [ 31.922533] stdp4028_ge_b850v3_fw_remove+0x34/0x60 [megachips_stdpxxxx_ge_b850v3_fw]
    [ 31.923139] i2c_device_remove+0x181/0x1f0

    The two bridges (stdp2690, stdp4028) do not probe at the same time, so
    the driver does not call ge_b850v3_resgiter() when probing, causing the
    driver to try to remove the object that has not been initialized.

    Fix this by checking whether both the bridges are probed.

    Fixes: 11632d4aa2b3 ("drm/bridge: megachips: Ensure both bridges are probed before registration")
    Signed-off-by: Zheyu Ma <zheyuma97@gmail.com>
    Signed-off-by: Robert Foss <robert.foss@linaro.org>
    Link: https://patchwork.freedesktop.org/patch/msgid/20220830073450.1897020-1-zheyuma97@gmail.com
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/gpu/drm/bridge/megachips-stdpxxxx-ge-b850v3-fw.c | 4 +++-
    1 file changed, 3 insertions(+), 1 deletion(-)

    diff --git a/drivers/gpu/drm/bridge/megachips-stdpxxxx-ge-b850v3-fw.c b/drivers/gpu/drm/bridge/megachips-stdpxxxx-ge-b850v3-fw.c
    index cce98bf2a4e7..72248a565579 100644
    --- a/drivers/gpu/drm/bridge/megachips-stdpxxxx-ge-b850v3-fw.c
    +++ b/drivers/gpu/drm/bridge/megachips-stdpxxxx-ge-b850v3-fw.c
    @@ -296,7 +296,9 @@ static void ge_b850v3_lvds_remove(void)
    * This check is to avoid both the drivers
    * removing the bridge in their remove() function
    */
    - if (!ge_b850v3_lvds_ptr)
    + if (!ge_b850v3_lvds_ptr ||
    + !ge_b850v3_lvds_ptr->stdp2690_i2c ||
    + !ge_b850v3_lvds_ptr->stdp4028_i2c)
    goto out;

    drm_bridge_remove(&ge_b850v3_lvds_ptr->bridge);
    --
    2.35.1


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