commit b1f3b64d76cf88cc250e5cdd1de783ba9737078e
author Dave Reisner <dreisner@archlinux.org> Sat Sep 08 11:55:45 2012 -0400
committer Jens Axboe <axboe@kernel.dk> Sun Sep 09 10:39:18 2012 +0200
tree c7ec8496a2b9a8af239fa78090f65178f30063c7
parent bf800ef1816b4283a885e55ad38068aec9711e4d

block: reject invalid queue attribute values

Instead of using simple_strtoul which "converts" invalid numbers to 0,
use strict_strtoul and perform error checking to ensure that userspace
passes us a valid unsigned long. This addresses problems with functions
such as writev, which might want to write a trailing newline -- the
newline should rightfully be rejected, but the value preceeding it
should be preserved.

Fixes BZ#46981.

Signed-off-by: Dave Reisner <dreisner@archlinux.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-sysfs.c

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 9628b29..ea51d82 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -26,9 +26,15 @@
 static ssize_t
 queue_var_store(unsigned long *var, const char *page, size_t count)
 {
-	char *p = (char *) page;
+	int err;
+	unsigned long v;
 
-	*var = simple_strtoul(p, &p, 10);
+	err = strict_strtoul(page, 10, &v);
+	if (err || v > UINT_MAX)
+		return -EINVAL;
+
+	*var = v;
+
 	return count;
 }
 
@@ -48,6 +54,9 @@
 		return -EINVAL;
 
 	ret = queue_var_store(&nr, page, count);
+	if (ret < 0)
+		return ret;
+
 	if (nr < BLKDEV_MIN_RQ)
 		nr = BLKDEV_MIN_RQ;
 
@@ -102,6 +111,9 @@
 	unsigned long ra_kb;
 	ssize_t ret = queue_var_store(&ra_kb, page, count);
 
+	if (ret < 0)
+		return ret;
+
 	q->backing_dev_info.ra_pages = ra_kb >> (PAGE_CACHE_SHIFT - 10);
 
 	return ret;
@@ -176,6 +188,9 @@
 			page_kb = 1 << (PAGE_CACHE_SHIFT - 10);
 	ssize_t ret = queue_var_store(&max_sectors_kb, page, count);
 
+	if (ret < 0)
+		return ret;
+
 	if (max_sectors_kb > max_hw_sectors_kb || max_sectors_kb < page_kb)
 		return -EINVAL;
 
@@ -236,6 +251,9 @@
 	unsigned long nm;
 	ssize_t ret = queue_var_store(&nm, page, count);
 
+	if (ret < 0)
+		return ret;
+
 	spin_lock_irq(q->queue_lock);
 	queue_flag_clear(QUEUE_FLAG_NOMERGES, q);
 	queue_flag_clear(QUEUE_FLAG_NOXMERGES, q);
@@ -264,6 +282,9 @@
 	unsigned long val;
 
 	ret = queue_var_store(&val, page, count);
+	if (ret < 0)
+		return ret;
+
 	spin_lock_irq(q->queue_lock);
 	if (val == 2) {
 		queue_flag_set(QUEUE_FLAG_SAME_COMP, q);