[PATCH 3/3] usb-storage: alauda: fix out-of-bounds zone index

[Arka Mondal <arka@arkamondal.net>]

MEDIA_INFO(us).lba_to_pba and .pba_to_lba are arrays of num_zones
pointers, allocated by kcalloc() in alauda_init_media().
alauda_ensure_map_for_zone() reads lba_to_pba[zone] and
pba_to_lba[zone], and when either is NULL alauda_read_map() writes a
pointer back to both. Two separate errors let zone reach num_zones, one
element past the end.

max_lba is capacity >> (blockshift + pageshift), which counts physical
blocks, but zone is lba / uzonesize and uzonesize is 125/128 of
zonesize. On a 16 MB card (alauda_card_ids id 0x73) num_zones is 1 and
uzonesize is 1000, so lba 1000 to 1023 pass the bounds check and index
element 1 of a one-element array.

alauda_read_data() also calls alauda_ensure_map_for_zone() before it
compares lba against max_lba, so any larger lba is used as an index
before the check rejects it. alauda_write_data() already checks first.

Bound lba by num_zones * uzonesize on both paths and move the read
side's call below the check. alauda_transport() reports
num_zones * uzonesize * blocksize for READ_CAPACITY, so the new bound is
exactly the range the device advertises and no block becomes
unreachable.

sd never issues an lba past the reported capacity; an SG_IO READ_10 can.

Fixes: e80b0fade09e ("[PATCH] USB Storage: add alauda support")
Suggested-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Arka Mondal <arka@arkamondal.net>
---
 drivers/usb/storage/alauda.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/drivers/usb/storage/alauda.c b/drivers/usb/storage/alauda.c
index d47ce01d519a..5e7f99ba8ac0 100644
--- a/drivers/usb/storage/alauda.c
+++ b/drivers/usb/storage/alauda.c
@@ -949,6 +949,7 @@ static int alauda_read_data(struct us_data *us, unsigned long address,
 	unsigned char *buffer;
 	u16 lba, max_lba;
 	unsigned int page, len, offset;
+	unsigned int num_zones;
 	unsigned int blockshift = MEDIA_INFO(us).blockshift;
 	unsigned int pageshift = MEDIA_INFO(us).pageshift;
 	unsigned int blocksize = MEDIA_INFO(us).blocksize;
@@ -973,7 +974,9 @@ static int alauda_read_data(struct us_data *us, unsigned long address,
 	/* Figure out the initial LBA and page */
 	lba = address >> blockshift;
 	page = (address & MEDIA_INFO(us).blockmask);
-	max_lba = MEDIA_INFO(us).capacity >> (blockshift + pageshift);
+	num_zones = MEDIA_INFO(us).capacity >> (MEDIA_INFO(us).zoneshift
+		+ blockshift + pageshift);
+	max_lba = num_zones * uzonesize;
 
 	result = USB_STOR_TRANSPORT_GOOD;
 	offset = 0;
@@ -985,10 +988,6 @@ static int alauda_read_data(struct us_data *us, unsigned long address,
 		unsigned int pages;
 		u16 pba;
 
-		result = alauda_ensure_map_for_zone(us, zone);
-		if (result != USB_STOR_TRANSPORT_GOOD)
-			break;
-
 		/* Not overflowing capacity? */
 		if (lba >= max_lba) {
 			usb_stor_dbg(us, "Error: Requested lba %u exceeds maximum %u\n",
@@ -997,6 +996,10 @@ static int alauda_read_data(struct us_data *us, unsigned long address,
 			break;
 		}
 
+		result = alauda_ensure_map_for_zone(us, zone);
+		if (result != USB_STOR_TRANSPORT_GOOD)
+			break;
+
 		/* Find number of pages we can read in this block */
 		pages = min(sectors, blocksize - page);
 		len = pages << pageshift;
@@ -1052,6 +1055,7 @@ static int alauda_write_data(struct us_data *us, unsigned long address,
 	unsigned int pagesize = MEDIA_INFO(us).pagesize;
 	struct scatterlist *sg;
 	u16 lba, max_lba;
+	unsigned int num_zones;
 	int result;
 
 	/*
@@ -1078,7 +1082,9 @@ static int alauda_write_data(struct us_data *us, unsigned long address,
 	/* Figure out the initial LBA and page */
 	lba = address >> blockshift;
 	page = (address & MEDIA_INFO(us).blockmask);
-	max_lba = MEDIA_INFO(us).capacity >> (pageshift + blockshift);
+	num_zones = MEDIA_INFO(us).capacity >> (MEDIA_INFO(us).zoneshift
+		+ blockshift + pageshift);
+	max_lba = num_zones * MEDIA_INFO(us).uzonesize;
 
 	result = USB_STOR_TRANSPORT_GOOD;
 	offset = 0;
-- 
2.55.0