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[Dvdrtools-users] [Fwd: data corruption in 2.4.19/drivers/scsi/sg.c]
From: |
Andy Polyakov |
Subject: |
[Dvdrtools-users] [Fwd: data corruption in 2.4.19/drivers/scsi/sg.c] |
Date: |
Wed, 21 Aug 2002 10:00:10 +0200 |
Of potential interest to subscribers of this list. I'm writing
"potential" because I haven't actually experience the problem
with cdrecord (maybe yet, kernel could have managed to keep
buffers neatly aligned while talking to cdrecord those times
I tries). It's VMware that is immediately affected by this. A.
-------- Original Message --------
Subject: data corruption in 2.4.19/drivers/scsi/sg.c
Date: Wed, 21 Aug 2002 01:49:12 +0200
From: Andy Polyakov <address@hidden>
To: address@hidden
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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