Re: [PATCH 08/10][next] scsi: aacraid: Replace one-element array with flexible-array member in struct sgmap

Gustavo A. R. Silva
2023-06-28T21:21:50Z

On 6/28/23 14:36, Kees Cook wrote:
> On Wed, Jun 28, 2023 at 11:57:13AM -0600, Gustavo A. R. Silva wrote:
>> Replace one-element array with flexible-array member in struct
>> sgmap and refactor the rest of the code, accordingly.
>>
>> Issue found with the help of Coccinelle and audited and fixed,
>> manually.
>
> This change _does_ have binary output differences, although it looks
> like you got most of them. I still see:
>
> commsup.o:
> - mov $0x40,%edx
> + mov $0x38,%edx
>
> This appears to be the sizeof() here:
>
> ret = aac_fib_send(ScsiPortCommand64, fibptr, sizeof(struct aac_srb),
> FsaNormal, 1, 1, NULL, NULL);
>
> struct aac_srb includes struct sgmap. I think this needs to explicitly
> include the 1 sgmap, which seems to be sent in the fibptr:

I see your point. Yeah; this is one of those cases of nested struct-with-flex-array.

The flex-array is a couple of layers into the main enclosing structure.

However, I would like to have the input of a maintainer here, just to confirm
this would be the expected change.

Thanks a lot for the feedback! :)
--
Gustavo

>
> srbcmd = (struct aac_srb *)fib_data(fibptr);
> ...
> sg64 = (struct sgmap64 *)&srbcmd->sg;
> sg64->count = cpu_to_le32(1);
>
> i.e. "sending 1". This seems to fix it:
>
> - ret = aac_fib_send(ScsiPortCommand64, fibptr, sizeof(struct aac_srb),
> + ret = aac_fib_send(ScsiPortCommand64, fibptr,
> + struct_size(srbcmd, sg.sg, 1),
>
> Then I see changes in both aac_write_block() and aac_scsi_32(), but they
> match the changes you made to get the correct size (it's just an easier
> calculation for the compiler to perform, so the code is slightly
> simplified).
>
> So I think with the hunk I suggested at the start, and a comment on the
> (expected) binary changes, this should be good to go.
>
> -Kees
>
>> Link: https://github.com/KSPP/linux/issues/79
>> Link: https://github.com/ClangBuiltLinux/linux/issues/1851
>> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
>> ---
>> drivers/scsi/aacraid/aachba.c | 24 ++++++++++--------------
>> drivers/scsi/aacraid/aacraid.h | 2 +-
>> drivers/scsi/aacraid/commctrl.c | 4 ++--
>> drivers/scsi/aacraid/comminit.c | 3 +--
>> 4 files changed, 14 insertions(+), 19 deletions(-)
>>
>> diff --git a/drivers/scsi/aacraid/aachba.c b/drivers/scsi/aacraid/aachba.c
>> index 03ba974f6b2a..b2849e5cc104 100644
>> --- a/drivers/scsi/aacraid/aachba.c
>> +++ b/drivers/scsi/aacraid/aachba.c
>> @@ -1336,8 +1336,7 @@ static int aac_read_block(struct fib * fib, struct scsi_cmnd * cmd, u64 lba, u32
>> if (ret < 0)
>> return ret;
>> fibsize = sizeof(struct aac_read) +
>> - ((le32_to_cpu(readcmd->sg.count) - 1) *
>> - sizeof (struct sgentry));
>> + le32_to_cpu(readcmd->sg.count) * sizeof(struct sgentry);
>> BUG_ON (fibsize > (fib->dev->max_fib_size -
>> sizeof(struct aac_fibhdr)));
>> /*
>> @@ -1471,8 +1470,7 @@ static int aac_write_block(struct fib * fib, struct scsi_cmnd * cmd, u64 lba, u3
>> if (ret < 0)
>> return ret;
>> fibsize = sizeof(struct aac_write) +
>> - ((le32_to_cpu(writecmd->sg.count) - 1) *
>> - sizeof (struct sgentry));
>> + le32_to_cpu(writecmd->sg.count) * sizeof(struct sgentry);
>> BUG_ON (fibsize > (fib->dev->max_fib_size -
>> sizeof(struct aac_fibhdr)));
>> /*
>> @@ -1590,9 +1588,9 @@ static int aac_scsi_64(struct fib * fib, struct scsi_cmnd * cmd)
>> /*
>> * Build Scatter/Gather list
>> */
>> - fibsize = sizeof (struct aac_srb) - sizeof (struct sgentry) +
>> - ((le32_to_cpu(srbcmd->sg.count) & 0xff) *
>> - sizeof (struct sgentry64));
>> + fibsize = sizeof(struct aac_srb) +
>> + (le32_to_cpu(srbcmd->sg.count) & 0xff) *
>> + sizeof(struct sgentry64);
>> BUG_ON (fibsize > (fib->dev->max_fib_size -
>> sizeof(struct aac_fibhdr)));
>>
>> @@ -1621,9 +1619,9 @@ static int aac_scsi_32(struct fib * fib, struct scsi_cmnd * cmd)
>> /*
>> * Build Scatter/Gather list
>> */
>> - fibsize = sizeof (struct aac_srb) +
>> - (((le32_to_cpu(srbcmd->sg.count) & 0xff) - 1) *
>> - sizeof (struct sgentry));
>> + fibsize = sizeof(struct aac_srb) +
>> + (le32_to_cpu(srbcmd->sg.count) & 0xff) *
>> + sizeof(struct sgentry);
>> BUG_ON (fibsize > (fib->dev->max_fib_size -
>> sizeof(struct aac_fibhdr)));
>>
>> @@ -1691,8 +1689,7 @@ static int aac_send_safw_bmic_cmd(struct aac_dev *dev,
>> fibptr->hw_fib_va->header.XferState &=
>> ~cpu_to_le32(FastResponseCapable);
>>
>> - fibsize = sizeof(struct aac_srb) - sizeof(struct sgentry) +
>> - sizeof(struct sgentry64);
>> + fibsize = sizeof(struct aac_srb) + sizeof(struct sgentry64);
>>
>> /* allocate DMA buffer for response */
>> addr = dma_map_single(&dev->pdev->dev, xfer_buf, xfer_len,
>> @@ -2264,8 +2261,7 @@ int aac_get_adapter_info(struct aac_dev* dev)
>> dev->a_ops.adapter_bounds = aac_bounds_32;
>> dev->scsi_host_ptr->sg_tablesize = (dev->max_fib_size -
>> sizeof(struct aac_fibhdr) -
>> - sizeof(struct aac_write) + sizeof(struct sgentry)) /
>> - sizeof(struct sgentry);
>> + sizeof(struct aac_write)) / sizeof(struct sgentry);
>> if (dev->dac_support) {
>> dev->a_ops.adapter_read = aac_read_block64;
>> dev->a_ops.adapter_write = aac_write_block64;
>> diff --git a/drivers/scsi/aacraid/aacraid.h b/drivers/scsi/aacraid/aacraid.h
>> index 94eb83d38be6..3fbc22ae72b6 100644
>> --- a/drivers/scsi/aacraid/aacraid.h
>> +++ b/drivers/scsi/aacraid/aacraid.h
>> @@ -507,7 +507,7 @@ struct sge_ieee1212 {
>>
>> struct sgmap {
>> __le32 count;
>> - struct sgentry sg[1];
>> + struct sgentry sg[];
>> };
>>
>> struct user_sgmap {
>> diff --git a/drivers/scsi/aacraid/commctrl.c b/drivers/scsi/aacraid/commctrl.c
>> index e7cc927ed952..df811ad4afaa 100644
>> --- a/drivers/scsi/aacraid/commctrl.c
>> +++ b/drivers/scsi/aacraid/commctrl.c
>> @@ -561,8 +561,8 @@ static int aac_send_raw_srb(struct aac_dev* dev, void __user * arg)
>> rcode = -EINVAL;
>> goto cleanup;
>> }
>> - actual_fibsize = sizeof(struct aac_srb) - sizeof(struct sgentry) +
>> - ((user_srbcmd->sg.count & 0xff) * sizeof(struct sgentry));
>> + actual_fibsize = sizeof(struct aac_srb) +
>> + (user_srbcmd->sg.count & 0xff) * sizeof(struct sgentry);
>> actual_fibsize64 = actual_fibsize + (user_srbcmd->sg.count & 0xff) *
>> (sizeof(struct sgentry64) - sizeof(struct sgentry));
>> /* User made a mistake - should not continue */
>> diff --git a/drivers/scsi/aacraid/comminit.c b/drivers/scsi/aacraid/comminit.c
>> index bd99c5492b7d..d8dd89c87b01 100644
>> --- a/drivers/scsi/aacraid/comminit.c
>> +++ b/drivers/scsi/aacraid/comminit.c
>> @@ -523,8 +523,7 @@ struct aac_dev *aac_init_adapter(struct aac_dev *dev)
>> dev->max_fib_size = sizeof(struct hw_fib);
>> dev->sg_tablesize = host->sg_tablesize = (dev->max_fib_size
>> - sizeof(struct aac_fibhdr)
>> - - sizeof(struct aac_write) + sizeof(struct sgentry))
>> - / sizeof(struct sgentry);
>> + - sizeof(struct aac_write)) / sizeof(struct sgentry);
>> dev->comm_interface = AAC_COMM_PRODUCER;
>> dev->raw_io_interface = dev->raw_io_64 = 0;
>>
>> --
>> 2.34.1
>>
>