mtd: m25p80: fix null pointer dereference bug

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Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=edcb3b14863e1a6aa1923eeaa81125a00cf51a80
Commit:     edcb3b14863e1a6aa1923eeaa81125a00cf51a80
Parent:     37d0892c5a94e208cf863e3b7bac014edee4346d
Author:     Anton Vorontsov <avorontsov at ru.mvista.com>
AuthorDate: Thu Aug 6 15:18:37 2009 -0700
Committer:  David Woodhouse <David.Woodhouse at intel.com>
CommitDate: Thu Sep 3 13:58:02 2009 +0100

    mtd: m25p80: fix null pointer dereference bug
    
    This patch fixes the following oops, observed with MTD_PARTITIONS=n:
    
    m25p80 spi32766.0: m25p80 (1024 Kbytes)
    Unable to handle kernel paging request for data at address 0x00000008
    Faulting instruction address: 0xc03a54b0
    Oops: Kernel access of bad area, sig: 11 [#1]
    Modules linked in:
    NIP: c03a54b0 LR: c03a5494 CTR: c01e98b8
    REGS: ef82bb60 TRAP: 0300   Not tainted  (2.6.31-rc4-00167-g4733fd3)
    MSR: 00029000 <EE,ME,CE>  CR: 24022022  XER: 20000000
    DEAR: 00000008, ESR: 00000000
    TASK = ef82c000[1] 'swapper' THREAD: ef82a000
    GPR00: 00000000 ef82bc10 ef82c000 0000002e 00001eb8 ffffffff c01e9824 00000036
    GPR08: c054ed40 c0542a08 00001eb8 00004000 22022022 1001a1a0 3ff8fd00 00000000
    GPR16: 00000000 00000001 00000000 00000000 ef82bddc c0530000 efbef500 ef8356d0
    GPR24: 00000000 ef8356d0 00000000 efbf7a00 c0530ec4 ffffffed efbf5300 c0541f98
    NIP [c03a54b0] m25p_probe+0x22c/0x354
    LR [c03a5494] m25p_probe+0x210/0x354
    Call Trace:
    [ef82bc10] [c03a5494] m25p_probe+0x210/0x354 (unreliable)
    [ef82bca0] [c024e37c] spi_drv_probe+0x2c/0x3c
    [ef82bcb0] [c01f1afc] driver_probe_device+0xa4/0x178
    [ef82bcd0] [c01f06e8] bus_for_each_drv+0x6c/0xa8
    [ef82bd00] [c01f1a34] device_attach+0x84/0xa8
    ...
    
    Signed-off-by: Anton Vorontsov <avorontsov at ru.mvista.com>
    Cc: David Brownell <david-b at pacbell.net>
    Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
    Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy at nokia.com>
    Signed-off-by: David Woodhouse <David.Woodhouse at intel.com>
---
 drivers/mtd/devices/m25p80.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/mtd/devices/m25p80.c b/drivers/mtd/devices/m25p80.c
index ae5fe91..10ed195 100644
--- a/drivers/mtd/devices/m25p80.c
+++ b/drivers/mtd/devices/m25p80.c
@@ -736,7 +736,7 @@ static int __devinit m25p_probe(struct spi_device *spi)
 			flash->partitioned = 1;
 			return add_mtd_partitions(&flash->mtd, parts, nr_parts);
 		}
-	} else if (data->nr_parts)
+	} else if (data && data->nr_parts)
 		dev_warn(&spi->dev, "ignoring %d default partitions on %s\n",
 				data->nr_parts, data->name);