Re: [PATCH v3 4/5] mtd: rawnand: brcmnand: Fix potential out-of-bounds access in oob write

William Zhang
2023-07-05T00:43:20Z

[-- Attachment #1: Type: text/plain, Size: 2687 bytes --]

Hi Miquel,

On 07/04/2023 08:28 AM, Miquel Raynal wrote:
> Hi William,
>
> william.zhang@broadcom.com wrote on Tue, 27 Jun 2023 12:37:37 -0700:
>
>> When the oob buffer length is not in multiple of words, the oob write
>> function does out-of-bounds read on the oob source buffer at the last
>> iteration. Fix that by always checking length limit on the oob buffer
>> read and fill with 0xff when reaching the end of the buffer to the oob
>> registers.
>>
>> Fixes: 27c5b17cd1b1 ("mtd: nand: add NAND driver "library" for Broadcom STB NAND controller")
>
> Wrong Fixes.
Same here. The function write_oob_to_regs was added by this commit and
no change since then.

>
> Missing Cc stable.
Will add
>
>> Signed-off-by: William Zhang <william.zhang@broadcom.com>
>> Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
>>
>> ---
>>
>> Changes in v3:
>> - Fix kernel test robot sparse warning:
>> drivers/mtd/nand/raw/brcmnand/brcmnand.c:1500:54: sparse: expected unsigned int [usertype] data
>> drivers/mtd/nand/raw/brcmnand/brcmnand.c:1500:54: sparse: got restricted __be32 [usertype]
>>
>> Changes in v2:
>> - Handle the remaining unaligned oob data after the oob data write loop
>>
>> drivers/mtd/nand/raw/brcmnand/brcmnand.c | 13 +++++++++++--
>> 1 file changed, 11 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/mtd/nand/raw/brcmnand/brcmnand.c b/drivers/mtd/nand/raw/brcmnand/brcmnand.c
>> index ea03104692bf..407bf79cbaf4 100644
>> --- a/drivers/mtd/nand/raw/brcmnand/brcmnand.c
>> +++ b/drivers/mtd/nand/raw/brcmnand/brcmnand.c
>> @@ -1477,19 +1477,28 @@ static int write_oob_to_regs(struct brcmnand_controller *ctrl, int i,
>> const u8 *oob, int sas, int sector_1k)
>> {
>> int tbytes = sas << sector_1k;
>> - int j;
>> + int j, k = 0;
>> + u32 last = 0xffffffff;
>> + u8 *plast = (u8 *)&last;
>>
>> /* Adjust OOB values for 1K sector size */
>> if (sector_1k && (i & 0x01))
>> tbytes = max(0, tbytes - (int)ctrl->max_oob);
>> tbytes = min_t(int, tbytes, ctrl->max_oob);
>>
>> - for (j = 0; j < tbytes; j += 4)
>> + for (j = 0; (j + 3) < tbytes; j += 4)
>
> Maybe a comment here as well to mention that you stop at the last
> iteration? Otherwise, just reading the line does not make you choice
> obvious.
>
Will add comment.

>> oob_reg_write(ctrl, j,
>> (oob[j + 0] << 24) |
>> (oob[j + 1] << 16) |
>> (oob[j + 2] << 8) |
>> (oob[j + 3] << 0));
>> +
>> + while (j < tbytes)
>> + plast[k++] = oob[j++];
>> +
>> + if (tbytes & 0x3)
>> + oob_reg_write(ctrl, (tbytes & ~0x3), (__force u32)cpu_to_be32(last));
>> +
>> return tbytes;
>> }
>>
>
>
> Thanks,
> Miquèl