[PATCH 4.9 75/80] ipmi: Fix kernel panic at ipmi_ssif_thread()

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Joeseph Chang <joechang@xxxxxxxxxxxxxx>

commit 6de65fcfdb51835789b245203d1bfc8d14cb1e06 upstream.

msg_written_handler() may set ssif_info->multi_data to NULL
when using ipmitool to write fru.

Before setting ssif_info->multi_data to NULL, add new local
pointer "data_to_send" and store correct i2c data pointer to
it to fix NULL pointer kernel panic and incorrect ssif_info->multi_pos.

Signed-off-by: Joeseph Chang <joechang@xxxxxxxxxxxxxx>
Signed-off-by: Corey Minyard <cminyard@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/char/ipmi/ipmi_ssif.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/char/ipmi/ipmi_ssif.c
+++ b/drivers/char/ipmi/ipmi_ssif.c
@@ -892,6 +892,7 @@ static void msg_written_handler(struct s
 		 * for details on the intricacies of this.
 		 */
 		int left;
+		unsigned char *data_to_send;
 
 		ssif_inc_stat(ssif_info, sent_messages_parts);
 
@@ -900,6 +901,7 @@ static void msg_written_handler(struct s
 			left = 32;
 		/* Length byte. */
 		ssif_info->multi_data[ssif_info->multi_pos] = left;
+		data_to_send = ssif_info->multi_data + ssif_info->multi_pos;
 		ssif_info->multi_pos += left;
 		if (left < 32)
 			/*
@@ -913,7 +915,7 @@ static void msg_written_handler(struct s
 		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,
+				  data_to_send,
 				  I2C_SMBUS_BLOCK_DATA);
 		if (rv < 0) {
 			/* request failed, just return the error. */