[PATCH] USB: usb-storage: Prevent divide-by-0 error in isd200_ata_command

[Alan Stern]

The isd200 sub-driver in usb-storage uses the HEADS and SECTORS values
in the ATA ID information to calculate cylinder and head values when
creating a CDB for READ or WRITE commands.  The calculation involves
division and modulus operations, which will cause a crash if either of
these values is 0.  While this never happens with a genuine device, it
could happen with a flawed or subversive emulation, as reported by the 
syzbot fuzzer.

Protect against this possibility by refusing to bind to the device if
either the ATA_ID_HEADS or ATA_ID_SECTORS value in the device's ID
information is 0.  This requires isd200_Initialization() to return a
negative error code when initialization fails; currently it always
returns 0 (even when there is an error).

Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Reported-and-tested-by: syzbot+28748250ab47a8f04100@xxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://lore.kernel.org/linux-usb/0000000000003eb868061245ba7f@xxxxxxxxxx/
Fixes: 1da177e4c3f4 ("v2.6.12-rc2")
Cc: <stable@xxxxxxxxxxxxxxx>

---

 drivers/usb/storage/isd200.c |   23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

Index: usb-devel/drivers/usb/storage/isd200.c
===================================================================
--- usb-devel.orig/drivers/usb/storage/isd200.c
+++ usb-devel/drivers/usb/storage/isd200.c
@@ -1105,7 +1105,7 @@ static void isd200_dump_driveid(struct u
 static int isd200_get_inquiry_data( struct us_data *us )
 {
 	struct isd200_info *info = (struct isd200_info *)us->extra;
-	int retStatus = ISD200_GOOD;
+	int retStatus;
 	u16 *id = info->id;
 
 	usb_stor_dbg(us, "Entering isd200_get_inquiry_data\n");
@@ -1137,6 +1137,13 @@ static int isd200_get_inquiry_data( stru
 				isd200_fix_driveid(id);
 				isd200_dump_driveid(us, id);
 
+				/* Prevent division by 0 in isd200_scsi_to_ata() */
+				if (id[ATA_ID_HEADS] == 0 || id[ATA_ID_SECTORS] == 0) {
+					usb_stor_dbg(us, "   Invalid ATA Identify data\n");
+					retStatus = ISD200_ERROR;
+					goto Done;
+				}
+
 				memset(&info->InquiryData, 0, sizeof(info->InquiryData));
 
 				/* Standard IDE interface only supports disks */
@@ -1202,6 +1209,7 @@ static int isd200_get_inquiry_data( stru
 		}
 	}
 
+ Done:
 	usb_stor_dbg(us, "Leaving isd200_get_inquiry_data %08X\n", retStatus);
 
 	return(retStatus);
@@ -1481,22 +1489,27 @@ static int isd200_init_info(struct us_da
 
 static int isd200_Initialization(struct us_data *us)
 {
+	int rc = 0;
+
 	usb_stor_dbg(us, "ISD200 Initialization...\n");
 
 	/* Initialize ISD200 info struct */
 
-	if (isd200_init_info(us) == ISD200_ERROR) {
+	if (isd200_init_info(us) < 0) {
 		usb_stor_dbg(us, "ERROR Initializing ISD200 Info struct\n");
+		rc = -ENOMEM;
 	} else {
 		/* Get device specific data */
 
-		if (isd200_get_inquiry_data(us) != ISD200_GOOD)
+		if (isd200_get_inquiry_data(us) != ISD200_GOOD) {
 			usb_stor_dbg(us, "ISD200 Initialization Failure\n");
-		else
+			rc = -EINVAL;
+		} else {
 			usb_stor_dbg(us, "ISD200 Initialization complete\n");
+		}
 	}
 
-	return 0;
+	return rc;
 }