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nsp32: fix an off by one

PATCH New Dan Carpenter 1 participant 1 message Apr 3, 2014

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PATCH 1/1 nsp32: fix an off by one

This off by one bug will cause memory corruption when we use every sglun.

The problem is that NSP32_SG_TABLE_SIZE is too small. Here is how it's caculated in the original code:

sizeof(nsp32_sgtable) * NSP32_SG_SIZE * MAX_TARGET * MAX_LUN

But the problem is that the NSP32_SG_SIZE should be (NSP32_SG_SIZE + 1) like this:

	sizeof(nsp32_sgtable) * (NSP32_SG_SIZE + 1) * MAX_TARGET * MAX_LUN

Or another more intuitive way to write it would be:

sizeof(nsp32_sglun) * MAX_TARGET * MAX_LUN

We use NSP32_SG_TABLE_SIZE to allocate data->sg_list which is an array of nsp32_sglun structs. The array has MAX_TARGET * MAX_LUN elements.

MAX_TARGET (8) * MAX_LUN (8) = 64 elements. The missing "+ 1" means that we only allocate enough space for 63 elements. In terms of bytes, the old code allocated 65536 bytes and now it allocates 66048 bytes.

---
Static checker stuff.

drivers/scsi/nsp32.h +1 -1
index c022182..d94f4cd 100644
@@ -454,7 +454,7 @@ typedef struct _nsp32_sgtable {
 typedef struct _nsp32_sglun {
 	nsp32_sgtable sgt[NSP32_SG_SIZE+1];	/* SG table */
 } __attribute__ ((packed)) nsp32_sglun;
-#define NSP32_SG_TABLE_SIZE (sizeof(nsp32_sgtable) * NSP32_SG_SIZE * MAX_TARGET * MAX_LUN)
+#define NSP32_SG_TABLE_SIZE (sizeof(nsp32_sglun) * MAX_TARGET * MAX_LUN)
 
 /* Auto parameter mode memory map.   */
 /* All values must be little endian. */