[PATCH] scsi: core: fix parsing of scsi {add,remove}-single-device

[Tony Battersby]

When parsing the "scsi add-single-device" and
"scsi remove-single-device" commands written to /proc/scsi/scsi, make
sure the parser doesn't skip over the NUL string terminator and read
past the end of the user-supplied string.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Tony Battersby <tonyb@xxxxxxxxxxxxxxx>
---
 drivers/scsi/scsi_proc.c | 48 +++++++++++++++++++++++++++++++---------
 1 file changed, 37 insertions(+), 11 deletions(-)

diff --git a/drivers/scsi/scsi_proc.c b/drivers/scsi/scsi_proc.c
index 4a6eb1741be0..b27c8da83e62 100644
--- a/drivers/scsi/scsi_proc.c
+++ b/drivers/scsi/scsi_proc.c
@@ -406,7 +406,7 @@ static ssize_t proc_scsi_write(struct file *file, const char __user *buf,
 			       size_t length, loff_t *ppos)
 {
 	int host, channel, id, lun;
-	char *buffer, *p;
+	char *buffer, *end, *p;
 	int err;
 
 	if (!buf || length > PAGE_SIZE)
@@ -421,10 +421,14 @@ static ssize_t proc_scsi_write(struct file *file, const char __user *buf,
 		goto out;
 
 	err = -EINVAL;
-	if (length < PAGE_SIZE)
-		buffer[length] = '\0';
-	else if (buffer[PAGE_SIZE-1])
-		goto out;
+	if (length < PAGE_SIZE) {
+		end = buffer + length;
+		*end = '\0';
+	} else {
+		end = buffer + PAGE_SIZE - 1;
+		if (*end)
+			goto out;
+	}
 
 	/*
 	 * Usage: echo "scsi add-single-device 0 1 2 3" >/proc/scsi/scsi
@@ -432,11 +436,22 @@ static ssize_t proc_scsi_write(struct file *file, const char __user *buf,
 	 */
 	if (!strncmp("scsi add-single-device", buffer, 22)) {
 		p = buffer + 23;
+		if (p >= end)
+			goto out;
 
 		host = simple_strtoul(p, &p, 0);
-		channel = simple_strtoul(p + 1, &p, 0);
-		id = simple_strtoul(p + 1, &p, 0);
-		lun = simple_strtoul(p + 1, &p, 0);
+		if (++p >= end)
+			goto out;
+
+		channel = simple_strtoul(p, &p, 0);
+		if (++p >= end)
+			goto out;
+
+		id = simple_strtoul(p, &p, 0);
+		if (++p >= end)
+			goto out;
+
+		lun = simple_strtoul(p, &p, 0);
 
 		err = scsi_add_single_device(host, channel, id, lun);
 
@@ -446,11 +461,22 @@ static ssize_t proc_scsi_write(struct file *file, const char __user *buf,
 	 */
 	} else if (!strncmp("scsi remove-single-device", buffer, 25)) {
 		p = buffer + 26;
+		if (p >= end)
+			goto out;
 
 		host = simple_strtoul(p, &p, 0);
-		channel = simple_strtoul(p + 1, &p, 0);
-		id = simple_strtoul(p + 1, &p, 0);
-		lun = simple_strtoul(p + 1, &p, 0);
+		if (++p >= end)
+			goto out;
+
+		channel = simple_strtoul(p, &p, 0);
+		if (++p >= end)
+			goto out;
+
+		id = simple_strtoul(p, &p, 0);
+		if (++p >= end)
+			goto out;
+
+		lun = simple_strtoul(p, &p, 0);
 
 		err = scsi_remove_single_device(host, channel, id, lun);
 	}
-- 
2.25.1