Date:   Mon, 28 Sep 2020 09:46:22 +0200
From:   Michael Walle <michael@...le.cc>
To:     Krzysztof Kozlowski <krzk@...nel.org>
Cc:     Vladimir Oltean <olteanv@...il.com>, linux-spi@...r.kernel.org,
        linux-kernel@...r.kernel.org, Mark Brown <broonie@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>
Subject: Re: [PATCH] spi: fsl-dspi: fix NULL pointer dereference

Am 2020-09-28 09:29, schrieb Krzysztof Kozlowski:
> On Mon, 28 Sep 2020 at 01:28, Vladimir Oltean <olteanv@...il.com> 
> wrote:
>> 
>> On Mon, Sep 28, 2020 at 12:43:36AM +0200, Michael Walle wrote:
>> > Since commit 530b5affc675 ("spi: fsl-dspi: fix use-after-free in remove
>> > path") this driver causes a kernel oops:
>> >
>> > [    1.891065] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000080
>> > [    1.899889] Mem abort info:
>> > [    1.902692]   ESR = 0x96000004
>> > [    1.905754]   EC = 0x25: DABT (current EL), IL = 32 bits
>> > [    1.911089]   SET = 0, FnV = 0
>> > [    1.914156]   EA = 0, S1PTW = 0
>> > [    1.917303] Data abort info:
>> > [    1.920193]   ISV = 0, ISS = 0x00000004
>> > [    1.924044]   CM = 0, WnR = 0
>> > [    1.927022] [0000000000000080] user address but active_mm is swapper
>> > [    1.933403] Internal error: Oops: 96000004 [#1] PREEMPT SMP
>> > [    1.938995] Modules linked in:
>> > [    1.942060] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.9.0-rc6-next-20200925-00026-gae556cc74e28-dirty #94
>> > [    1.951838] Hardware name: Kontron SMARC-sAL28 (Single PHY) on SMARC Eval 2.0 carrier (DT)
>> > [    1.960135] pstate: 40000005 (nZcv daif -PAN -UAO -TCO BTYPE=--)
>> > [    1.966168] pc : dspi_setup+0xc8/0x2e0
>> > [    1.969926] lr : dspi_setup+0xbc/0x2e0
>> > [    1.973684] sp : ffff80001139b930
>> > [    1.977005] x29: ffff80001139b930 x28: ffff00207a5d2000
>> > [    1.982338] x27: 0000000000000006 x26: ffff00207a44d410
>> > [    1.987669] x25: ffff002079c08100 x24: ffff00207a5d2400
>> > [    1.993000] x23: ffff00207a5d2600 x22: ffff800011169948
>> > [    1.998332] x21: ffff800010cbcd20 x20: ffff00207a58a800
>> > [    2.003663] x19: ffff00207a76b700 x18: 0000000000000010
>> > [    2.008994] x17: 0000000000000001 x16: 0000000000000019
>> > [    2.014326] x15: ffffffffffffffff x14: 0720072007200720
>> > [    2.019657] x13: 0720072007200720 x12: ffff8000111fc5e0
>> > [    2.024989] x11: 0000000000000003 x10: ffff8000111e45a0
>> > [    2.030320] x9 : 0000000000000000 x8 : ffff00207a76b780
>> > [    2.035651] x7 : 0000000000000000 x6 : 000000000000003f
>> > [    2.040982] x5 : 0000000000000040 x4 : ffff80001139b918
>> > [    2.046313] x3 : 0000000000000001 x2 : 64b62cc917af5100
>> > [    2.051643] x1 : 0000000000000000 x0 : 0000000000000000
>> > [    2.056973] Call trace:
>> > [    2.059425]  dspi_setup+0xc8/0x2e0
>> > [    2.062837]  spi_setup+0xcc/0x248
>> > [    2.066160]  spi_add_device+0xb4/0x198
>> > [    2.069918]  of_register_spi_device+0x250/0x370
>> > [    2.074462]  spi_register_controller+0x4f4/0x770
>> > [    2.079094]  dspi_probe+0x5bc/0x7b0
>> > [    2.082594]  platform_drv_probe+0x5c/0xb0
>> > [    2.086615]  really_probe+0xec/0x3c0
>> > [    2.090200]  driver_probe_device+0x60/0xc0
>> > [    2.094308]  device_driver_attach+0x7c/0x88
>> > [    2.098503]  __driver_attach+0x60/0xe8
>> > [    2.102263]  bus_for_each_dev+0x7c/0xd0
>> > [    2.106109]  driver_attach+0x2c/0x38
>> > [    2.109692]  bus_add_driver+0x194/0x1f8
>> > [    2.113538]  driver_register+0x6c/0x128
>> > [    2.117385]  __platform_driver_register+0x50/0x60
>> > [    2.122105]  fsl_dspi_driver_init+0x24/0x30
>> > [    2.126302]  do_one_initcall+0x54/0x2d0
>> > [    2.130149]  kernel_init_freeable+0x1ec/0x258
>> > [    2.134520]  kernel_init+0x1c/0x120
>> > [    2.138018]  ret_from_fork+0x10/0x34
>> > [    2.141606] Code: 97e0b11d aa0003f3 b4000680 f94006e0 (f9404000)
>> > [    2.147723] ---[ end trace 26cf63e6cbba33a8 ]---
>> > [    2.152374] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
>> > [    2.160061] SMP: stopping secondary CPUs
>> > [    2.163999] Kernel Offset: disabled
>> > [    2.167496] CPU features: 0x0040022,20006008
>> > [    2.171777] Memory Limit: none
>> > [    2.174840] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b ]---
>> >
>> > This is because since this commit, the allocation of the drivers private
>> > data is done explicitly and in this case spi_alloc_master() won't set the
>> > correct pointer.
>> >
>> > Fixes: 530b5affc675 ("spi: fsl-dspi: fix use-after-free in remove path")
>> > Signed-off-by: Michael Walle <michael@...le.cc>
>> > ---
>> 
>> Sascha, how did you test commit 530b5affc675?
> 
> Hi,
> 
> I just hit it on my Vybrid systems as well. It fails on every boot, so
> I have doubts that it was actually tested. The fix was posted on 23rd
> and applied within a few hours... also no time for anyone else to test
> it.

Mhh, given the benefit of the doubt, I could imagine that the allocs 
align up in a way, that the pointer is valid afterwards, no?

>> 
>> >  drivers/spi/spi-fsl-dspi.c | 2 ++
>> >  1 file changed, 2 insertions(+)
>> >
>> > diff --git a/drivers/spi/spi-fsl-dspi.c b/drivers/spi/spi-fsl-dspi.c
>> > index a939618f5e47..dd80be987bf9 100644
>> > --- a/drivers/spi/spi-fsl-dspi.c
>> > +++ b/drivers/spi/spi-fsl-dspi.c
>> > @@ -1236,6 +1236,8 @@ static int dspi_probe(struct platform_device *pdev)
>> >       if (!ctlr)
>> >               return -ENOMEM;
>> >
>> > +     spi_controller_set_devdata(ctlr, dspi);
> 
> Michael,
> 
> How about moving here platform_set_drvdata(pdev, dspi) from the end of
> the probe to keep them close to each other?

Given that this patch has a fixes tag, I'd rather keep the changes to a 
minimum to avoid future conflicts.

OTOH I don't know if its better if the "move platform_set_drvdata()" is 
in a seperate patch, conflict-wise.

Any suggestions?

-michael

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