[PATCH] scsi: arcmsr: Avoid over-read of sense buffer

[Kees Cook]

In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memcpy(), memmove(), and memset(), avoid
intentionally reading across neighboring array fields.

pcmd->sense_buffer is 96 bytes, and was being manually zero-filled.
However, struct SENSE_DATA is 18 bytes, with ccb->arcmsr_cdb.SenseData
only being 15 bytes, resulting in a 3 byte over-read.

Copy only the contents of ccb->arcmsr_cdb.SenseData and zero fill the
remainder, avoiding potential over-reads.

Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
 drivers/scsi/arcmsr/arcmsr_hba.c | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/drivers/scsi/arcmsr/arcmsr_hba.c b/drivers/scsi/arcmsr/arcmsr_hba.c
index e5149c9fd4e6..ec1a834c922d 100644
--- a/drivers/scsi/arcmsr/arcmsr_hba.c
+++ b/drivers/scsi/arcmsr/arcmsr_hba.c
@@ -1323,16 +1323,19 @@ static void arcmsr_ccb_complete(struct CommandControlBlock *ccb)
 
 static void arcmsr_report_sense_info(struct CommandControlBlock *ccb)
 {
-
 	struct scsi_cmnd *pcmd = ccb->pcmd;
-	struct SENSE_DATA *sensebuffer = (struct SENSE_DATA *)pcmd->sense_buffer;
+
 	pcmd->result = (DID_OK << 16) | SAM_STAT_CHECK_CONDITION;
-	if (sensebuffer) {
-		int sense_data_length =
-			sizeof(struct SENSE_DATA) < SCSI_SENSE_BUFFERSIZE
-			? sizeof(struct SENSE_DATA) : SCSI_SENSE_BUFFERSIZE;
-		memset(sensebuffer, 0, SCSI_SENSE_BUFFERSIZE);
-		memcpy(sensebuffer, ccb->arcmsr_cdb.SenseData, sense_data_length);
+	if (pcmd->sense_buffer) {
+		struct SENSE_DATA *sensebuffer;
+
+		memcpy_and_pad(pcmd->sense_buffer,
+			       SCSI_SENSE_BUFFERSIZE,
+			       ccb->arcmsr_cdb.SenseData,
+			       sizeof(ccb->arcmsr_cdb.SenseData),
+			       0);
+
+		sensebuffer = (struct SENSE_DATA *)pcmd->sense_buffer;
 		sensebuffer->ErrorCode = SCSI_SENSE_CURRENT_ERRORS;
 		sensebuffer->Valid = 1;
 	}
-- 
2.25.1