Re: [PATCH] mtd: pxa3xx_nand: fix driver when num_cs is 0

[Ezequiel Garcia <ezequiel.garcia@free-electrons.com>]

On 02/08/2015 05:02 PM, Robert Jarzmik wrote:
> As the devicetree binding doesn't require num_cs to exist or be strictly
> positive, and neither does the platform data case, a bug appear when
> num_cs is set to 0 and panics the kernel.
> 
> The issue is that in alloc_nand_resource(), chip is dereferenced without
> having a value assigned when num_cs == 0.
> 
> Fix this by returning ENODEV is num_cs == 0.
> 
> The panic seen is :
> Unable to handle kernel NULL pointer dereference at virtual address 000002b8
> pgd = c0004000
> [000002b8] *pgd=00000000
> Internal error: Oops: 5 [#1] PREEMPT ARM
> Modules linked in:
> Hardware name: Marvell PXA3xx (Device Tree Support)
> task: c3822aa0 ti: c3826000 task.ti: c3826000
> PC is at alloc_nand_resource+0x180/0x4a8
> LR is at alloc_nand_resource+0xa0/0x4a8
> pc : [<c0275b90>]    lr : [<c0275ab0>]    psr: 68000013
> sp : c3827d90  ip : 00000000  fp : 00000000
> r10: c3862200  r9 : 0000005e  r8 : 00000000
> r7 : c3865610  r6 : c3862210  r5 : c3924210  r4 : c3862200
> r3 : 00000000  r2 : 00000000  r1 : 00000000  r0 : 00000000
> Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment kernel
> Control: 0000397f  Table: 80004018  DAC: 00000035
> Process swapper (pid: 1, stack limit = 0xc3826198)
> Stack: (0xc3827d90 to 0xc3828000)
> ...zip...
> [<c0275b90>] (alloc_nand_resource) from [<c0275ff8>] (pxa3xx_nand_probe+0x140/0x978)
> [<c0275ff8>] (pxa3xx_nand_probe) from [<c0258c40>] (platform_drv_probe+0x48/0xa4)
> [<c0258c40>] (platform_drv_probe) from [<c0257650>] (driver_probe_device+0x80/0x21c)
> [<c0257650>] (driver_probe_device) from [<c0257878>] (__driver_attach+0x8c/0x90)
> [<c0257878>] (__driver_attach) from [<c0255ec4>] (bus_for_each_dev+0x58/0x88)
> [<c0255ec4>] (bus_for_each_dev) from [<c0256ec8>] (bus_add_driver+0xd8/0x1d4)
> [<c0256ec8>] (bus_add_driver) from [<c0257f14>] (driver_register+0x78/0xf4)
> [<c0257f14>] (driver_register) from [<c00088a8>] (do_one_initcall+0x80/0x1e4)
> [<c00088a8>] (do_one_initcall) from [<c048ed08>] (kernel_init_freeable+0xec/0x1b4)
> [<c048ed08>] (kernel_init_freeable) from [<c0377d8c>] (kernel_init+0x8/0xe4)
> [<c0377d8c>] (kernel_init) from [<c00095f8>] (ret_from_fork+0x14/0x3c)
> Code: e503b234 e5953008 e1530001 caffffd1 (e59002b8)
> ---[ end trace a5770060c8441895 ]---
> 
> Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
> ---
>  drivers/mtd/nand/pxa3xx_nand.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/mtd/nand/pxa3xx_nand.c b/drivers/mtd/nand/pxa3xx_nand.c
> index 96b0b1d..4a2df63 100644
> --- a/drivers/mtd/nand/pxa3xx_nand.c
> +++ b/drivers/mtd/nand/pxa3xx_nand.c
> @@ -1572,6 +1572,8 @@ static int alloc_nand_resource(struct platform_device *pdev)
>  	int ret, irq, cs;
>  
>  	pdata = dev_get_platdata(&pdev->dev);
> +	if (pdata->num_cs <= 0)
> +		return -ENODEV;
>  	info = devm_kzalloc(&pdev->dev, sizeof(*info) + (sizeof(*mtd) +
>  			    sizeof(*host)) * pdata->num_cs, GFP_KERNEL);
>  	if (!info)
> 

Looks good,

Acked-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>

-- 
Ezequiel García, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com