2022-02-02 10:04:42

by Ira Weiny

Subject: [PATCH V6 08/10] cxl/cdat: Introduce cdat_hdr_valid()

From: Ira Weiny <[email protected]>

The CDAT data is protected by a checksum which should be checked when
the CDAT is read to ensure it is valid. In addition the lengths
specified should be checked.

Introduce cdat_hdr_valid() to check the checksum. While at it check and
store the sequence number.

Signed-off-by: Ira Weiny <[email protected]>

---
Changes from V5
New patch, split out
Update cdat_hdr_valid()
Remove revision and cs field parsing
There is no point in these
Add seq check and debug print.
---
drivers/cxl/cdat.h | 2 ++
drivers/cxl/pci.c | 32 ++++++++++++++++++++++++++++++++
2 files changed, 34 insertions(+)

diff --git a/drivers/cxl/cdat.h b/drivers/cxl/cdat.h
index 4722b6bbbaf0..a7725d26f2d2 100644
--- a/drivers/cxl/cdat.h
+++ b/drivers/cxl/cdat.h
@@ -88,10 +88,12 @@
*
* @table: cache of CDAT table
* @length: length of cached CDAT table
+ * @seq: Last read Sequence number of the CDAT table
*/
struct cxl_cdat {
void *table;
size_t length;
+ u32 seq;
};

#endif /* !__CXL_CDAT_H__ */
diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
index 28b973a9e29e..c362c75feed2 100644
--- a/drivers/cxl/pci.c
+++ b/drivers/cxl/pci.c
@@ -586,6 +586,35 @@ static int cxl_setup_doe_devices(struct cxl_dev_state *cxlds)
return 0;
}

+static bool cxl_cdat_hdr_valid(struct device *dev, struct cxl_cdat *cdat)
+{
+ u32 *table = cdat->table;
+ u8 *data8 = cdat->table;
+ u32 length, seq;
+ u8 check;
+ int i;
+
+ length = FIELD_GET(CDAT_HEADER_DW0_LENGTH, table[0]);
+ if (length < CDAT_HEADER_LENGTH_BYTES)
+ return false;
+
+ if (length > cdat->length)
+ return false;
+
+ seq = FIELD_GET(CDAT_HEADER_DW3_SEQUENCE, table[3]);
+
+ /* Store the sequence for now. */
+ if (cdat->seq != seq) {
+ dev_info(dev, "CDAT seq change %x -> %x\n", cdat->seq, seq);
+ cdat->seq = seq;
+ }
+
+ for (check = 0, i = 0; i < length; i++)
+ check += data8[i];
+
+ return check == 0;
+}
+
#define CDAT_DOE_REQ(entry_handle) \
(FIELD_PREP(CXL_DOE_TABLE_ACCESS_REQ_CODE, \
CXL_DOE_TABLE_ACCESS_REQ_CODE_READ) | \
@@ -658,6 +687,9 @@ static int cxl_cdat_read_table(struct cxl_dev_state *cxlds,

} while (entry_handle != 0xFFFF);

+ if (!cxl_cdat_hdr_valid(cxlds->dev, cdat))
+ return -EIO;
+
return 0;
}

--
2.31.1

2022-02-02 15:44:18

by Ben Widawsky

Subject: Re: [PATCH V6 08/10] cxl/cdat: Introduce cdat_hdr_valid()

On 22-01-31 23:19:50, [email protected] wrote:
> From: Ira Weiny <[email protected]>
>
> The CDAT data is protected by a checksum which should be checked when
> the CDAT is read to ensure it is valid. In addition the lengths
> specified should be checked.
>
> Introduce cdat_hdr_valid() to check the checksum. While at it check and
> store the sequence number.
>
> Signed-off-by: Ira Weiny <[email protected]>
>
> ---
> Changes from V5
> New patch, split out
> Update cdat_hdr_valid()
> Remove revision and cs field parsing
> There is no point in these
> Add seq check and debug print.
> ---
> drivers/cxl/cdat.h | 2 ++
> drivers/cxl/pci.c | 32 ++++++++++++++++++++++++++++++++
> 2 files changed, 34 insertions(+)
>
> diff --git a/drivers/cxl/cdat.h b/drivers/cxl/cdat.h
> index 4722b6bbbaf0..a7725d26f2d2 100644
> --- a/drivers/cxl/cdat.h
> +++ b/drivers/cxl/cdat.h
> @@ -88,10 +88,12 @@
> *
> * @table: cache of CDAT table
> * @length: length of cached CDAT table
> + * @seq: Last read Sequence number of the CDAT table
> */
> struct cxl_cdat {
> void *table;
> size_t length;
> + u32 seq;
> };
>
> #endif /* !__CXL_CDAT_H__ */
> diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> index 28b973a9e29e..c362c75feed2 100644
> --- a/drivers/cxl/pci.c
> +++ b/drivers/cxl/pci.c
> @@ -586,6 +586,35 @@ static int cxl_setup_doe_devices(struct cxl_dev_state *cxlds)
> return 0;
> }
>
> +static bool cxl_cdat_hdr_valid(struct device *dev, struct cxl_cdat *cdat)
> +{
> + u32 *table = cdat->table;
> + u8 *data8 = cdat->table;
> + u32 length, seq;
> + u8 check;
> + int i;
> +
> + length = FIELD_GET(CDAT_HEADER_DW0_LENGTH, table[0]);
> + if (length < CDAT_HEADER_LENGTH_BYTES)
> + return false;
> +
> + if (length > cdat->length)
> + return false;
> +
> + seq = FIELD_GET(CDAT_HEADER_DW3_SEQUENCE, table[3]);
> +
> + /* Store the sequence for now. */
> + if (cdat->seq != seq) {
> + dev_info(dev, "CDAT seq change %x -> %x\n", cdat->seq, seq);
> + cdat->seq = seq;
> + }

If sequence hasn't changed you could short-circuit the checksum.

> +
> + for (check = 0, i = 0; i < length; i++)
> + check += data8[i];
> +
> + return check == 0;
> +}
> +
> #define CDAT_DOE_REQ(entry_handle) \
> (FIELD_PREP(CXL_DOE_TABLE_ACCESS_REQ_CODE, \
> CXL_DOE_TABLE_ACCESS_REQ_CODE_READ) | \
> @@ -658,6 +687,9 @@ static int cxl_cdat_read_table(struct cxl_dev_state *cxlds,
>
> } while (entry_handle != 0xFFFF);
>
> + if (!cxl_cdat_hdr_valid(cxlds->dev, cdat))
> + return -EIO;
> +
> return 0;
> }
>
> --
> 2.31.1
>