[PATCH] ipmi: Fix kernel panic at ipmi_ssif_thread()

[Joeseph Chang]

From: Joeseph Chang <joechang@xxxxxxxxxxxxxx>

msg_written_handler() may set ssif_info->multi_data to NULL
when using ipmitool to write fru.
Change the ssif i2c send data sequence in msg_written_handler()
to fix NULL pointer kernel panic and incorrect ssif_info->multi_pos.

Signed-off-by: Joeseph Chang <joechang@xxxxxxxxxxxxxx>
---
 drivers/char/ipmi/ipmi_ssif.c | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/drivers/char/ipmi/ipmi_ssif.c b/drivers/char/ipmi/ipmi_ssif.c
index cca6e5b..39346ee 100644
--- a/drivers/char/ipmi/ipmi_ssif.c
+++ b/drivers/char/ipmi/ipmi_ssif.c
@@ -899,21 +899,13 @@ static void msg_written_handler(struct ssif_info *ssif_info, int result,
 			left = 32;
 		/* Length byte. */
 		ssif_info->multi_data[ssif_info->multi_pos] = left;
-		ssif_info->multi_pos += left;
-		if (left < 32)
-			/*
-			 * Write is finished.  Note that we must end
-			 * with a write of less than 32 bytes to
-			 * complete the transaction, even if it is
-			 * zero bytes.
-			 */
-			ssif_info->multi_data = NULL;
 
 		rv = ssif_i2c_send(ssif_info, msg_written_handler,
 				  I2C_SMBUS_WRITE,
 				  SSIF_IPMI_MULTI_PART_REQUEST_MIDDLE,
 				  ssif_info->multi_data + ssif_info->multi_pos,
 				  I2C_SMBUS_BLOCK_DATA);
+
 		if (rv < 0) {
 			/* request failed, just return the error. */
 			ssif_inc_stat(ssif_info, send_errors);
@@ -922,6 +914,16 @@ static void msg_written_handler(struct ssif_info *ssif_info, int result,
 				pr_info("Error from i2c_non_blocking_op(3)\n");
 			msg_done_handler(ssif_info, -EIO, NULL, 0);
 		}
+
+		ssif_info->multi_pos += left;
+		if (left < 32)
+			/*
+			 * Write is finished.  Note that we must end
+			 * with a write of less than 32 bytes to
+			 * complete the transaction, even if it is
+			 * zero bytes.
+			 */
+			ssif_info->multi_data = NULL;
 	} else {
 		/* Ready to request the result. */
 		unsigned long oflags, *flags;
-- 
1.9.1