Re: [PATCH] mtd: rawnand: qcom: fix memory corruption that causes panic

[Miquel Raynal <miquel.raynal@bootlin.com>]

Hi Christian,

Christian Lamparter <chunkeey@gmail.com> wrote on Sun, 23 Dec 2018
01:31:26 +0100:

> This patch fixes a memory corruption that occurred in the
> qcom-nandc driver since it was converted to nand_scan().
> 
> On boot, an affected device will panic from a NPE at a weird place:
> | Unable to handle kernel NULL pointer dereference at virtual address 0
> | pgd = (ptrval)
> | [00000000] *pgd=00000000
> | Internal error: Oops: 80000005 [#1] SMP ARM
> | CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.19.9 #0
> | Hardware name: Generic DT based system
> | PC is at   (null)
> | LR is at nand_block_isbad+0x90/0xa4
> | pc : [<00000000>]    lr : [<c0592240>]    psr: 80000013
> | sp : cf839d40  ip : 00000000  fp : cfae9e20
> | r10: cf815810  r9 : 00000000  r8 : 00000000
> | r7 : 00000000  r6 : 00000000  r5 : 00000001  r4 : cf815810
> | r3 : 00000000  r2 : cfae9810  r1 : ffffffff  r0 : cf815810
> | Flags: Nzcv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
> | Control: 10c5387d  Table: 8020406a  DAC: 00000051
> | Process swapper/0 (pid: 1, stack limit = 0x(ptrval))
> | [<c0592240>] (nand_block_isbad) from [<c0580a94>]
> | [<c0580a94>] (allocate_partition) from [<c05811e4>]
> | [<c05811e4>] (add_mtd_partitions) from [<c0581164>]
> | [<c0581164>] (parse_mtd_partitions) from [<c057def4>]
> | [<c057def4>] (mtd_device_parse_register) from [<c059d274>]
> | [<c059d274>] (qcom_nandc_probe) from [<c0567f00>]
> 
> The problem is that the nand_scan()'s qcom_nand_attach_chip callback
> is updating the nandc->max_cwperpage from 1 to 4. This causes the
> sg_init_table of clear_bam_transaction() in the driver's
> qcom_nandc_block_bad() to memset much more than what was initially
> allocated by alloc_bam_transaction().
> 
> This patch restores the old behavior by reallocating the shared bam
> transaction alloc_bam_transaction() after the chip was identified,
> but before mtd_device_parse_register() (which is an alias for
> mtd_device_register() - see panic) gets called. This fixes the
> corruption and the driver is working again.
> 
> Cc: stable@vger.kernel.org
> Fixes: 6a3cec64f18c ("mtd: rawnand: qcom: convert driver to nand_scan()")
> Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
> ---

Acked-by: Miquel Raynal <miquel.raynal@bootlin.com>

Thanks,
Miquèl