From mboxrd@z Thu Jan 1 00:00:00 1970 From: Przemyslaw Marczak Date: Tue, 22 Oct 2013 13:04:20 +0200 Subject: [U-Boot] [PATCH 3/4] usb: ums: fix bug in partition capacity computation. In-Reply-To: <201310190257.20728.marex@denx.de> References: <1381929675-26165-1-git-send-email-p.marczak@samsung.com> <201310171941.20573.marex@denx.de> <52614E49.8010109@samsung.com> <201310190257.20728.marex@denx.de> Message-ID: <52665BB4.4040103@samsung.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de Hello Marek, On 10/19/2013 02:57 AM, Marek Vasut wrote: > Dear Przemyslaw Marczak, > >> Hi Marek, >> >> On 10/17/2013 07:41 PM, Marek Vasut wrote: >>> Dear Przemyslaw Marczak, >>> >>>> Before this change ums disk capacity was miscalculated because >>>> of integer overflow. >>>> >>>> Signed-off-by: Przemyslaw Marczak >>>> Cc: Marek Vasut >>>> --- >>>> >>>> board/samsung/common/ums.c | 16 ++++++++++++---- >>>> 1 file changed, 12 insertions(+), 4 deletions(-) >>>> >>>> diff --git a/board/samsung/common/ums.c b/board/samsung/common/ums.c >>>> index 1f28590..6c4e6c4 100644 >>>> --- a/board/samsung/common/ums.c >>>> +++ b/board/samsung/common/ums.c >>>> @@ -37,11 +37,19 @@ static int ums_write_sector(struct ums *ums_dev, >>>> >>>> static void ums_get_capacity(struct ums *ums_dev, long long int >>>> *capacity) { >>>> >>>> - long long int tmp_capacity; >>>> + int64_t mmc_capacity = (int64_t)ums_dev->mmc->capacity; >>> >>> Why are these casts here? >>> >>>> + int64_t ums_capacity = (int64_t)ums_dev->part_size * SECTOR_SIZE; >>>> + int64_t ums_offset = (int64_t)ums_dev->offset * SECTOR_SIZE; >>> >>> And here all around? And why are these values signed, can there ever be >>> negative value in them? >> >> I tried to fix it without changes in ums driver because it works fine. >> Of course capacity can't be a negative value. >> >> When we set some offset and some part size we have an integer overflow >> >> at this line, just before cast to long long int: >>>> - tmp_capacity = (long long int)((ums_dev->offset + ums_dev->part_size) >>>> - * SECTOR_SIZE); >>>> - *capacity = ums_dev->mmc->capacity - tmp_capacity; >> >> In the best case of overflow - ums partition capacity will have the same >> value as mmc cap, but if offset was set, then the partition size will be >> exceeded. >> >>>> + if (ums_capacity && ((ums_capacity + ums_offset) < mmc_capacity)) >>>> + *capacity = ums_capacity; >>>> + else >>>> + *capacity = mmc_capacity - ums_offset; >>> >>> Urgh, what exactly does this code achieve again? >> >> This code above avoids situation when tmp_capacity value is bigger than >> real mmc capacity. I don't check next the offset but this is also the >> reason why I put printf here. I assume that developer should know how to >> define UMS_START_BLOCK and UMS_PART_SIZE if no, some information will be >> printed. >> >>>> + printf("UMS: partition capacity: %#llx blocks\n" >>>> + "UMS: partition start block: %#x\n", >>>> + *capacity / SECTOR_SIZE, >>>> + ums_dev->offset); >>>> >>>> } >>>> >>>> static struct ums ums_dev = { >>> >>> Best regards, >>> Marek Vasut >> >> In summary I will change signed variables to unsigned here and few in >> the ums gadget driver. >> Moreover now I think that it will be better to replace part_size from >> the struct ums_dev with part_blk_num and compute its value at ums_init >> function. And then pointer to ums_get_capacity is not needed in ums >> structure. >> >> What do you think about this? > > I think the first screaming thing here is ... why is this all multiplied by > SECTOR_SIZE before doing the comparisons and stuffs ? You can do that later > (that does mean do it later, yes). You're right, but actually we don't need to use real card capacity but only sector count. Patch v2 will include this. > > Try this: > > u64 mmc_cap = ums_dev->mmc->capacity / SECTOR_SIZE; > u64 ums_start = ums_dev->offset; > u64 ums_end = ums_start + ums_dev->part_size; > > /* Start past MMC size. */ > if (ums_start >= mmc_cap) > return -EINVAL; > > /* End past MMC size. */ > if (ums_end > mmc_cap) { > puts("UMS region larger than MMC device, capping\n"); > ums_end = mmc_cap; > } > > *capacity = (ums_end - ums_start) * SECTOR_SIZE; > > Does this work? You'd need to add debug. > It will only work if UMS_PART_SIZE and UMS_START_BLOCK are set correctly. In default case when both values are defined as 0 - function returns null capacity but we don't want this. Patch v2 will include cases for default, valid and bad definitions of UMS_PART_SIZE and UMS_START_BLOCK. I will also remove unnecessary code around capacity validation from ums gadget driver. Next patch set will be send soon. Regards -- Przemyslaw Marczak Samsung R&D Institute Poland Samsung Electronics p.marczak at samsung.com