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    Subject[PATCH 5.10 714/717] rtc: ep93xx: Fix NULL pointer dereference in ep93xx_rtc_read_time
    Date
    From: Nikita Shubin <nikita.shubin@maquefel.me>

    commit 00c33482bb6110bce8110daa351f9b3baf4df7dc upstream.

    Mismatch in probe platform_set_drvdata set's and method's that call
    dev_get_platdata will result in "Unable to handle kernel NULL pointer
    dereference", let's use according method for getting driver data after
    platform_set_drvdata.

    8<--- cut here ---
    Unable to handle kernel NULL pointer dereference at virtual address 00000000
    pgd = (ptrval)
    [00000000] *pgd=00000000
    Internal error: Oops: 5 [#1] ARM
    Modules linked in:
    CPU: 0 PID: 1 Comm: swapper Not tainted 5.9.10-00003-g723e101e0037-dirty #4
    Hardware name: Technologic Systems TS-72xx SBC
    PC is at ep93xx_rtc_read_time+0xc/0x2c
    LR is at __rtc_read_time+0x4c/0x8c
    [...]
    [<c02b01c8>] (ep93xx_rtc_read_time) from [<c02ac38c>] (__rtc_read_time+0x4c/0x8c)
    [<c02ac38c>] (__rtc_read_time) from [<c02ac3f8>] (rtc_read_time+0x2c/0x4c)
    [<c02ac3f8>] (rtc_read_time) from [<c02acc54>] (__rtc_read_alarm+0x28/0x358)
    [<c02acc54>] (__rtc_read_alarm) from [<c02abd80>] (__rtc_register_device+0x124/0x2ec)
    [<c02abd80>] (__rtc_register_device) from [<c02b028c>] (ep93xx_rtc_probe+0xa4/0xac)
    [<c02b028c>] (ep93xx_rtc_probe) from [<c026424c>] (platform_drv_probe+0x24/0x5c)
    [<c026424c>] (platform_drv_probe) from [<c0262918>] (really_probe+0x218/0x374)
    [<c0262918>] (really_probe) from [<c0262da0>] (device_driver_attach+0x44/0x60)
    [<c0262da0>] (device_driver_attach) from [<c0262e70>] (__driver_attach+0xb4/0xc0)
    [<c0262e70>] (__driver_attach) from [<c0260d44>] (bus_for_each_dev+0x68/0xac)
    [<c0260d44>] (bus_for_each_dev) from [<c026223c>] (driver_attach+0x18/0x24)
    [<c026223c>] (driver_attach) from [<c0261dd8>] (bus_add_driver+0x150/0x1b4)
    [<c0261dd8>] (bus_add_driver) from [<c026342c>] (driver_register+0xb0/0xf4)
    [<c026342c>] (driver_register) from [<c0264210>] (__platform_driver_register+0x30/0x48)
    [<c0264210>] (__platform_driver_register) from [<c04cb9ac>] (ep93xx_rtc_driver_init+0x10/0x1c)
    [<c04cb9ac>] (ep93xx_rtc_driver_init) from [<c000973c>] (do_one_initcall+0x7c/0x1c0)
    [<c000973c>] (do_one_initcall) from [<c04b9ecc>] (kernel_init_freeable+0x168/0x1ac)
    [<c04b9ecc>] (kernel_init_freeable) from [<c03b2228>] (kernel_init+0x8/0xf4)
    [<c03b2228>] (kernel_init) from [<c00082c0>] (ret_from_fork+0x14/0x34)
    Exception stack(0xc441dfb0 to 0xc441dff8)
    dfa0: 00000000 00000000 00000000 00000000
    dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
    dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
    Code: e12fff1e e92d4010 e590303c e1a02001 (e5933000)
    ---[ end trace c914d6030eaa95c8 ]---

    Fixes: b809d192eb98 ("rtc: ep93xx: stop setting platform_data")
    Signed-off-by: Nikita Shubin <nikita.shubin@maquefel.me>
    Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
    Cc: stable@vger.kernel.org
    Link: https://lore.kernel.org/r/20201201095507.10317-1-nikita.shubin@maquefel.me
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/rtc/rtc-ep93xx.c | 6 +++---
    1 file changed, 3 insertions(+), 3 deletions(-)

    --- a/drivers/rtc/rtc-ep93xx.c
    +++ b/drivers/rtc/rtc-ep93xx.c
    @@ -33,7 +33,7 @@ struct ep93xx_rtc {
    static int ep93xx_rtc_get_swcomp(struct device *dev, unsigned short *preload,
    unsigned short *delete)
    {
    - struct ep93xx_rtc *ep93xx_rtc = dev_get_platdata(dev);
    + struct ep93xx_rtc *ep93xx_rtc = dev_get_drvdata(dev);
    unsigned long comp;

    comp = readl(ep93xx_rtc->mmio_base + EP93XX_RTC_SWCOMP);
    @@ -51,7 +51,7 @@ static int ep93xx_rtc_get_swcomp(struct

    static int ep93xx_rtc_read_time(struct device *dev, struct rtc_time *tm)
    {
    - struct ep93xx_rtc *ep93xx_rtc = dev_get_platdata(dev);
    + struct ep93xx_rtc *ep93xx_rtc = dev_get_drvdata(dev);
    unsigned long time;

    time = readl(ep93xx_rtc->mmio_base + EP93XX_RTC_DATA);
    @@ -62,7 +62,7 @@ static int ep93xx_rtc_read_time(struct d

    static int ep93xx_rtc_set_time(struct device *dev, struct rtc_time *tm)
    {
    - struct ep93xx_rtc *ep93xx_rtc = dev_get_platdata(dev);
    + struct ep93xx_rtc *ep93xx_rtc = dev_get_drvdata(dev);
    unsigned long secs = rtc_tm_to_time64(tm);

    writel(secs + 1, ep93xx_rtc->mmio_base + EP93XX_RTC_LOAD);

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