data corruption in 2.4.19/drivers/scsi/sg.c

From: Andy Polyakov (appro@fy.chalmers.se)
Date: Tue Aug 20 2002 - 18:49:12 EST


Hi,

As subject suggests generic scsi module from 2.4.19 corrupts data.
Backing back to 2.4.18 code [as suggested below] fixes the problem.
>From the attached patch it's not clear what's causing the problem
as the code appears equivalent. Corruption occurs if you break out
the inner loop few lines later:

                if (ksglen > usglen) {
                    ...
                    p += usglen;
                    ksglen -= usglen;
                    break;
                }

and reenter it. Then ksglen and p are reset which results in some
duplicate data injection.

Cheers. Andy.

--- ./drivers/scsi/sg.c.orig Sat Aug 3 02:39:44 2002
+++ ./drivers/scsi/sg.c Wed Aug 21 00:44:16 2002
@@ -1884,11 +1884,16 @@
             res = sg_u_iovec(hp, iovec_count, j, 1, &usglen, &up);
             if (res) return res;
 
+#if 0
             for (; k < schp->k_use_sg; ++k, ++sclp) {
                 ksglen = (int)sclp->length;
                 p = sclp->address;
                 if (NULL == p)
                     break;
+#else
+ for (; (k < schp->k_use_sg) && p;
+ ++k, ++sclp, ksglen = (int)sclp->length, p = sclp->address) {
+#endif
                 ok = (SG_USER_MEM != mem_src_arr[k]);
                 if (usglen <= 0)
                     break;
@@ -2040,11 +2045,16 @@
             res = sg_u_iovec(hp, iovec_count, j, 0, &usglen, &up);
             if (res) return res;
 
+#if 0
             for (; k < schp->k_use_sg; ++k, ++sclp) {
                 ksglen = (int)sclp->length;
                 p = sclp->address;
                 if (NULL == p)
                     break;
+#else
+ for (; (k < schp->k_use_sg) && p;
+ ++k, ++sclp, ksglen = (int)sclp->length, p = sclp->address) {
+#endif
                 ok = (SG_USER_MEM != mem_src_arr[k]);
                 if (usglen <= 0)
                     break;
-
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