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>

1 files changed, 23 insertions, 2 deletions

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 9628b291f960..ea51d827a0bb 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -26,9 +26,15 @@ queue_var_show(unsigned long var, char *page)
 static ssize_t
 queue_var_store(unsigned long *var, const char *page, size_t count)
 {
-        char *p = (char *) page;
+        int err;
+        unsigned long v;
+
+        err = strict_strtoul(page, 10, &v);
+        if (err || v > UINT_MAX)
+                return -EINVAL;
+
+        *var = v;
 
-        *var = simple_strtoul(p, &p, 10);
         return count;
 }
 
@@ -48,6 +54,9 @@ queue_requests_store(struct request_queue *q, const char *page, size_t count)
                 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 @@ queue_ra_store(struct request_queue *q, const char *page, size_t count)
         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 @@ queue_max_sectors_store(struct request_queue *q, const char *page, size_t count)
                         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 @@ static ssize_t queue_nomerges_store(struct request_queue *q, const char *page,
         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 @@ queue_rq_affinity_store(struct request_queue *q, const char *page, size_t count)
         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);