[PATCH] block: reject invalid queue attribute values

[Dave Reisner]

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 <dreis...@archlinux.org>
---
 block/blk-sysfs.c | 25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

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 @@ 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);
-- 
1.7.12

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