From: David Milburn <dmilburn@redhat.com>
Subject: [RHEL5 PATCH] BZ 219838 sg: fix incorrect last scatg length
Date: Tue, 2 Jan 2007 15:40:31 -0500
Bugzilla: 219838
Message-Id: <20070102204031.GA7477@dhcp-210.hsv.redhat.com>
Changelog: [scsi] fix incorrect last scatg length


The sg driver can cause an oops by incorrectly setting the length
of the last element in a scatter gather list when the transfer
length is large and it is not a multiple of PAGE_SIZE. NEC can 
consistently reproduce this problem within minutes during heavy I/O 
stress on a Promise EX8350 system. NEC was provided a 
2.6.18-1.2840.el5 test kernel with this patch applied and was 
no longer able to reproduce the problem after 12+ hours of heavy
I/O stress. The test kernel also verified that without this patch
the length of the last element was getting set to a value larger
than the remaining size to transfer, this patch correctly sets
the length. This patch fixes IT	109386 / BZ 219838, please ACK
or comment.

Here is the upstream patch:

http://www.mail-archive.com/git-commits-head@vger.kernel.org/msg02227.html

Thanks,
David

--- linux-2.6.18.i686/drivers/scsi/sg.c.scatter
+++ linux-2.6.18.i686/drivers/scsi/sg.c
@@ -60,7 +60,7 @@ static int sg_version_num = 30534;	/* 2 
 
 #ifdef CONFIG_SCSI_PROC_FS
 #include <linux/proc_fs.h>
-static char *sg_version_date = "20060920";
+static char *sg_version_date = "20061027";
 
 static int sg_proc_init(void);
 static void sg_proc_cleanup(void);
@@ -710,12 +710,12 @@ sg_common_write(Sg_fd * sfp, Sg_request 
 			  (int) cmnd[0], (int) hp->cmd_len));
 
 	if ((k = sg_start_req(srp))) {
-		SCSI_LOG_TIMEOUT(1, printk("sg_write: start_req err=%d\n", k));
+		SCSI_LOG_TIMEOUT(1, printk("sg_common_write: start_req err=%d\n", k));
 		sg_finish_rem_req(srp);
 		return k;	/* probably out of space --> ENOMEM */
 	}
 	if ((k = sg_write_xfer(srp))) {
-		SCSI_LOG_TIMEOUT(1, printk("sg_write: write_xfer, bad address\n"));
+		SCSI_LOG_TIMEOUT(1, printk("sg_common_write: write_xfer, bad address\n"));
 		sg_finish_rem_req(srp);
 		return k;
 	}
@@ -746,7 +746,7 @@ sg_common_write(Sg_fd * sfp, Sg_request 
 				hp->dxfer_len, srp->data.k_use_sg, timeout,
 				SG_DEFAULT_RETRIES, srp, sg_cmd_done,
 				GFP_ATOMIC)) {
-		SCSI_LOG_TIMEOUT(1, printk("sg_write: scsi_execute_async failed\n"));
+		SCSI_LOG_TIMEOUT(1, printk("sg_common_write: scsi_execute_async failed\n"));
 		/*
 		 * most likely out of mem, but could also be a bad map
 		 */
@@ -1283,7 +1283,7 @@ sg_cmd_done(void *data, char *sense, int
 		sg_finish_rem_req(srp);
 		srp = NULL;
 		if (NULL == sfp->headrp) {
-			SCSI_LOG_TIMEOUT(1, printk("sg...bh: already closed, final cleanup\n"));
+			SCSI_LOG_TIMEOUT(1, printk("sg_cmd_done: already closed, final cleanup\n"));
 			if (0 == sg_remove_sfp(sdp, sfp)) {	/* device still present */
 				scsi_device_put(sdp->device);
 			}
@@ -1512,12 +1512,12 @@ sg_remove(struct class_device *cl_dev, s
 						    POLL_HUP);
 				}
 			}
-			SCSI_LOG_TIMEOUT(3, printk("sg_detach: dev=%d, dirty\n", k));
+			SCSI_LOG_TIMEOUT(3, printk("sg_remove: dev=%d, dirty\n", k));
 			if (NULL == sdp->headfp) {
 				sg_dev_arr[k] = NULL;
 			}
 		} else {	/* nothing active, simple case */
-			SCSI_LOG_TIMEOUT(3, printk("sg_detach: dev=%d\n", k));
+			SCSI_LOG_TIMEOUT(3, printk("sg_remove: dev=%d\n", k));
 			sg_dev_arr[k] = NULL;
 		}
 		sg_nr_dev--;
@@ -1876,14 +1876,15 @@ sg_build_indirect(Sg_scatter_hold * schp
 			}
 		}
 		sg->page = p;
-		sg->length = ret_sz;
+		sg->length = (ret_sz > num) ? num : ret_sz;
 
-		SCSI_LOG_TIMEOUT(5, printk("sg_build_build: k=%d, a=0x%p, len=%d\n",
-				  k, p, ret_sz));
+		SCSI_LOG_TIMEOUT(5, printk("sg_build_indirect: k=%d, num=%d, "
+				 "ret_sz=%d\n", k, num, ret_sz));
 	}		/* end of for loop */
 
 	schp->k_use_sg = k;
-	SCSI_LOG_TIMEOUT(5, printk("sg_build_indirect: k_use_sg=%d, rem_sz=%d\n", k, rem_sz));
+	SCSI_LOG_TIMEOUT(5, printk("sg_build_indirect: k_use_sg=%d, "
+			 "rem_sz=%d\n", k, rem_sz));
 
 	schp->bufflen = blk_size;
 	if (rem_sz > 0)	/* must have failed */
@@ -2014,7 +2015,7 @@ sg_remove_scat(Sg_scatter_hold * schp)
 			for (k = 0; (k < schp->k_use_sg) && sg->page;
 			     ++k, ++sg) {
 				SCSI_LOG_TIMEOUT(5, printk(
-				    "sg_remove_scat: k=%d, a=0x%p, len=%d\n",
+				    "sg_remove_scat: k=%d, pg=0x%p, len=%d\n",
 				    k, sg->page, sg->length));
 				sg_page_free(sg->page, sg->length);
 			}