block: fail op_is_write() requests to read-only partitions

Regular block device writes go through blkdev_write_iter(), which does
bdev_read_only(), while zeroout/discard/etc requests are never checked,
both userspace- and kernel-triggered.  Add a generic catch-all check to
generic_make_request_checks() to actually enforce ioctl(BLKROSET) and
set_disk_ro(), which is used by quite a few drivers for things like
snapshots, read-only backing files/images, etc.

Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 38 insertions, 18 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index 55f338020254..c21a16e9fdf9 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2062,6 +2062,21 @@ static inline bool should_fail_request(struct hd_struct *part,
 
 #endif /* CONFIG_FAIL_MAKE_REQUEST */
 
+static inline bool bio_check_ro(struct bio *bio, struct hd_struct *part)
+{
+        if (part->policy && op_is_write(bio_op(bio))) {
+                char b[BDEVNAME_SIZE];
+
+                printk(KERN_ERR
+                       "generic_make_request: Trying to write "
+                        "to read-only block-device %s (partno %d)\n",
+                        bio_devname(bio, b), part->partno);
+                return true;
+        }
+
+        return false;
+}
+
 /*
  * Remap block n of partition p to block n+start(p) of the disk.
  */
@@ -2070,27 +2085,28 @@ static inline int blk_partition_remap(struct bio *bio)
         struct hd_struct *p;
         int ret = 0;
 
+        rcu_read_lock();
+        p = __disk_get_part(bio->bi_disk, bio->bi_partno);
+        if (unlikely(!p || should_fail_request(p, bio->bi_iter.bi_size) ||
+                     bio_check_ro(bio, p))) {
+                ret = -EIO;
+                goto out;
+        }
+
         /*
          * Zone reset does not include bi_size so bio_sectors() is always 0.
          * Include a test for the reset op code and perform the remap if needed.
          */
-        if (!bio->bi_partno ||
-            (!bio_sectors(bio) && bio_op(bio) != REQ_OP_ZONE_RESET))
-                return 0;
+        if (!bio_sectors(bio) && bio_op(bio) != REQ_OP_ZONE_RESET)
+                goto out;
 
-        rcu_read_lock();
-        p = __disk_get_part(bio->bi_disk, bio->bi_partno);
-        if (likely(p && !should_fail_request(p, bio->bi_iter.bi_size))) {
-                bio->bi_iter.bi_sector += p->start_sect;
-                bio->bi_partno = 0;
-                trace_block_bio_remap(bio->bi_disk->queue, bio, part_devt(p),
-                                bio->bi_iter.bi_sector - p->start_sect);
-        } else {
-                printk("%s: fail for partition %d\n", __func__, bio->bi_partno);
-                ret = -EIO;
-        }
-        rcu_read_unlock();
+        bio->bi_iter.bi_sector += p->start_sect;
+        bio->bi_partno = 0;
+        trace_block_bio_remap(bio->bi_disk->queue, bio, part_devt(p),
+                              bio->bi_iter.bi_sector - p->start_sect);
 
+out:
+        rcu_read_unlock();
         return ret;
 }
 
@@ -2149,15 +2165,19 @@ generic_make_request_checks(struct bio *bio)
          * For a REQ_NOWAIT based request, return -EOPNOTSUPP
          * if queue is not a request based queue.
          */
-
         if ((bio->bi_opf & REQ_NOWAIT) && !queue_is_rq_based(q))
                 goto not_supported;
 
         if (should_fail_request(&bio->bi_disk->part0, bio->bi_iter.bi_size))
                 goto end_io;
 
-        if (blk_partition_remap(bio))
-                goto end_io;
+        if (!bio->bi_partno) {
+                if (unlikely(bio_check_ro(bio, &bio->bi_disk->part0)))
+                        goto end_io;
+        } else {
+                if (blk_partition_remap(bio))
+                        goto end_io;
+        }
 
         if (bio_check_eod(bio, nr_sectors))
                 goto end_io;