mtd: pxa3xx_nand: fix driver when num_cs is 0

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Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=e423c90a6520d704cd885d742b499dfd6b0f6277
Commit:     e423c90a6520d704cd885d742b499dfd6b0f6277
Parent:     8dad0386b97c4bd6edd56752ca7f2e735fe5beb4
Author:     Robert Jarzmik <robert.jarzmik at free.fr>
AuthorDate: Sun Feb 8 21:02:09 2015 +0100
Committer:  Brian Norris <computersforpeace at gmail.com>
CommitDate: Sat Feb 28 01:22:07 2015 -0800

    mtd: pxa3xx_nand: fix driver when num_cs is 0
    
    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 at free.fr>
    Acked-by: Ezequiel Garcia <ezequiel.garcia at free-electrons.com>
    Signed-off-by: Brian Norris <computersforpeace at gmail.com>
---
 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 bc67736..10b1f7a 100644
--- a/drivers/mtd/nand/pxa3xx_nand.c
+++ b/drivers/mtd/nand/pxa3xx_nand.c
@@ -1608,6 +1608,8 @@ 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)