Re: [PATCH] media: i2c: max9286: fix kernel oops when removing module

[Kieran Bingham]

Hi Laurentiu,

Quoting Laurentiu Palcu (2022-03-07 13:37:50)
> When removing the max9286 module we get a kernel oops:
> 
> Unable to handle kernel paging request at virtual address 000000aa00000094
> Mem abort info:
>   ESR = 0x96000004
>   EC = 0x25: DABT (current EL), IL = 32 bits
>   SET = 0, FnV = 0
>   EA = 0, S1PTW = 0
>   FSC = 0x04: level 0 translation fault
> Data abort info:
>   ISV = 0, ISS = 0x00000004
>   CM = 0, WnR = 0
> user pgtable: 4k pages, 48-bit VAs, pgdp=0000000880d85000
> [000000aa00000094] pgd=0000000000000000, p4d=0000000000000000
> Internal error: Oops: 96000004 [#1] PREEMPT SMP
> Modules linked in: fsl_jr_uio caam_jr rng_core libdes caamkeyblob_desc caamhash_desc caamalg_desc crypto_engine max9271 authenc crct10dif_ce mxc_jpeg_encdec
> CPU: 2 PID: 713 Comm: rmmod Tainted: G         C        5.15.5-00057-gaebcd29c8ed7-dirty #5
> Hardware name: Freescale i.MX8QXP MEK (DT)
> pstate: 80000005 (Nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : i2c_mux_del_adapters+0x24/0xf0
> lr : max9286_remove+0x28/0xd0 [max9286]
> sp : ffff800013a9bbf0
> x29: ffff800013a9bbf0 x28: ffff00080b6da940 x27: 0000000000000000
> x26: 0000000000000000 x25: 0000000000000000 x24: 0000000000000000
> x23: ffff000801a5b970 x22: ffff0008048b0890 x21: ffff800009297000
> x20: ffff0008048b0f70 x19: 000000aa00000064 x18: 0000000000000000
> x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000
> x14: 0000000000000014 x13: 0000000000000000 x12: ffff000802da49e8
> x11: ffff000802051918 x10: ffff000802da4920 x9 : ffff000800030098
> x8 : 0101010101010101 x7 : 7f7f7f7f7f7f7f7f x6 : fefefeff6364626d
> x5 : 8080808000000000 x4 : 0000000000000000 x3 : 0000000000000000
> x2 : ffffffffffffffff x1 : ffff00080b6da940 x0 : 0000000000000000
> Call trace:
>  i2c_mux_del_adapters+0x24/0xf0
>  max9286_remove+0x28/0xd0 [max9286]
>  i2c_device_remove+0x40/0x110
>  __device_release_driver+0x188/0x234
>  driver_detach+0xc4/0x150
>  bus_remove_driver+0x60/0xe0
>  driver_unregister+0x34/0x64
>  i2c_del_driver+0x58/0xa0
>  max9286_i2c_driver_exit+0x1c/0x490 [max9286]
>  __arm64_sys_delete_module+0x194/0x260
>  invoke_syscall+0x48/0x114
>  el0_svc_common.constprop.0+0xd4/0xfc
>  do_el0_svc+0x2c/0x94
>  el0_svc+0x28/0x80
>  el0t_64_sync_handler+0xa8/0x130
>  el0t_64_sync+0x1a0/0x1a4
> 
> The Oops happens because the I2C client data does not point to
> max9286_priv anymore but to v4l2_subdev. The change happened in
> max9286_init() which calls v4l2_i2c_subdev_init() later on...
> 

I think this needs a Fixes tag, but it looks like it happened when we
merged the driver. So that makes it:

Fixes: 66d8c9d2422d ("media: i2c: Add MAX9286 driver")

I see in max9286_probe() we set
	i2c_set_clientdata(client, (struct max9286_priv) priv);

And indeed, then we call 

max9286_init()
 max9286_v4l2_register()
  v4l2_i2c_subdev_init(&priv->sd, priv->client, &max9286_subdev_ops);

So I think this patch should probably also remove the call to 
i2c_set_clientdata() in probe to prevent confusion.



> Signed-off-by: Laurentiu Palcu <laurentiu.palcu@xxxxxxxxxxx>
> ---
>  drivers/media/i2c/max9286.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/media/i2c/max9286.c b/drivers/media/i2c/max9286.c
> index d2a4915ed9f7..04f5b7e3a9e5 100644
> --- a/drivers/media/i2c/max9286.c
> +++ b/drivers/media/i2c/max9286.c
> @@ -1385,7 +1385,7 @@ static int max9286_probe(struct i2c_client *client)
>  
>  static int max9286_remove(struct i2c_client *client)
>  {
> -       struct max9286_priv *priv = i2c_get_clientdata(client);
> +       struct max9286_priv *priv = sd_to_max9286(i2c_get_clientdata(client));

What happens if the module load failed before calling max9286_init(), in
that case, would the i2c_get_clientdata() return NULL?

If so, should this be checked?

--
Kieran


>  
>         i2c_mux_del_adapters(priv->mux);
>  
> -- 
> 2.17.1
>