Date: Sun, 11 Sep 2011 21:00:24 GMT From: Andreas Longwitz <longwitz@incore.de> To: freebsd-bugs@FreeBSD.org Subject: Re: kern/155658: [amr] [patch] amr_ioctl(): call of malloc() causes memory corruption and panic Message-ID: <201109112100.p8BL0O7J088441@freefall.freebsd.org>
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The following reply was made to PR kern/155658; it has been noted by GNATS.
From: Andreas Longwitz <longwitz@incore.de>
To: bug-followup@freebsd.org
Cc:
Subject: Re: kern/155658: [amr] [patch] amr_ioctl(): call of malloc() causes
memory corruption and panic
Date: Sun, 11 Sep 2011 22:58:17 +0200
As John Baldwin pointed out to me, this problem is caused by overrunnig
the memory buffer by a specific megarc command. Further analysis showed
that indeed this happens. There are several commands leading megarc to
acquire a buffer of 12868 bytes but in this case the controller always
sends back 25412 bytes. That is the memory corruption.
This problem can be patched in megarc, see ports/137938. But I have also
seen seen sporadic situations like this: megarc wants a buffer of 36
bytes, but the controller sends 1k data back. Therefore I think it is
the best to be on the safe side and allocate always a buffer big enough
for all answers of the controller.
The following patch now looks good for me:
--- amr.c.orig 2010-02-11 19:34:06.000000000 +0100
+++ amr.c 2011-09-09 16:23:07.000000000 +0200
@@ -87,6 +87,7 @@
#include <dev/amr/amrvar.h>
#define AMR_DEFINE_TABLES
#include <dev/amr/amr_tables.h>
+#define MAX_AMR_IOCTL 25600 /* observed: 25412 */
SYSCTL_NODE(_hw, OID_AUTO, amr, CTLFLAG_RD, 0, "AMR driver parameters");
@@ -843,7 +844,7 @@
/* handle inbound data buffer */
if (au_length != 0 && au_cmd[0] != 0x06) {
- if ((dp = malloc(au_length, M_AMR, M_WAITOK|M_ZERO)) == NULL) {
+ if ((dp = malloc(MAX_AMR_IOCTL, M_AMR, M_WAITOK|M_ZERO)) ==
NULL) {
error = ENOMEM;
goto out;
}
--
Dr. Andreas Longwitz
Data Service GmbH
Beethovenstr. 2A
23617 Stockelsdorf
Amtsgericht Lübeck, HRB 318 BS
Geschäftsführer: Wilfried Paepcke, Dr. Andreas Longwitz, Josef Flatau
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