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Subject: Re: [PATCH] spmi: Add a check for remove callback when removing a SPMI driver
From:   Stephen Boyd <sboyd@kernel.org>
Cc:     linux-arm-msm@vger.kernel.org, linux-arm-msm-owner@vger.kernel.org,
        Jishnu Prakash <quic_jprakash@quicinc.com>
To:     Jishnu Prakash <quic_jprakash@quicinc.com>, agross@kernel.org,
        devicetree@vger.kernel.org, gregkh@linuxfoundation.org,
        linus.walleij@linaro.org, linux-kernel@vger.kernel.org,
        quic_collinsd@quicinc.com, quic_kamalw@quicinc.com,
        quic_subbaram@quicinc.com, robh+dt@kernel.org
Date:   Wed, 12 Apr 2023 21:15:39 -0700
User-Agent: alot/0.10
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Quoting Jishnu Prakash (2022-12-20 21:37:12)
> When removing a SPMI driver, there can be a crash due to NULL pointer
> dereference if it does not have a remove callback defined. This is
> one such call trace observed when removing the QCOM SPMI PMIC driver:
>=20
>  dump_backtrace.cfi_jt+0x0/0x8
>  dump_stack_lvl+0xd8/0x16c
>  panic+0x188/0x498
>  __cfi_slowpath+0x0/0x214
>  __cfi_slowpath+0x1dc/0x214
>  spmi_drv_remove+0x16c/0x1e0
>  device_release_driver_internal+0x468/0x79c
>  driver_detach+0x11c/0x1a0
>  bus_remove_driver+0xc4/0x124
>  driver_unregister+0x58/0x84
>  cleanup_module+0x1c/0xc24 [qcom_spmi_pmic]
>  __do_sys_delete_module+0x3ec/0x53c
>  __arm64_sys_delete_module+0x18/0x28
>  el0_svc_common+0xdc/0x294
>  el0_svc+0x38/0x9c
>  el0_sync_handler+0x8c/0xf0
>  el0_sync+0x1b4/0x1c0
>=20
> If a driver has all its resources allocated through devm_() APIs and
> does not need any other explicit cleanup, it would not require a
> remove callback to be defined. Hence, add a check for remove callback
> presence before calling it when removing a SPMI driver.
>=20
> Signed-off-by: Jishnu Prakash <quic_jprakash@quicinc.com>
> ---

Applied to spmi-next