block: fix SG_[GS]ET_RESERVED_SIZE ioctl when max_sectors is huge

SG_GET_RESERVED_SIZE and SG_SET_RESERVED_SIZE ioctls access a reserved
buffer in bytes as int type.  The value needs to be capped at the request
queue's max_sectors.  But integer overflow is not correctly handled in
the calculation when converting max_sectors from sectors to bytes.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: "James E.J. Bottomley" <JBottomley@parallels.com>
Cc: Douglas Gilbert <dgilbert@interlog.com>
Cc: linux-scsi@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 11 insertions, 4 deletions

diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c
index 14695c6221c8..bda1497add4c 100644
--- a/block/scsi_ioctl.c
+++ b/block/scsi_ioctl.c
@@ -82,9 +82,18 @@ static int sg_set_timeout(struct request_queue *q, int __user *p)
         return err;
 }
 
+static int max_sectors_bytes(struct request_queue *q)
+{
+        unsigned int max_sectors = queue_max_sectors(q);
+
+        max_sectors = min_t(unsigned int, max_sectors, INT_MAX >> 9);
+
+        return max_sectors << 9;
+}
+
 static int sg_get_reserved_size(struct request_queue *q, int __user *p)
 {
-        unsigned val = min(q->sg_reserved_size, queue_max_sectors(q) << 9);
+        int val = min_t(int, q->sg_reserved_size, max_sectors_bytes(q));
 
         return put_user(val, p);
 }
@@ -98,10 +107,8 @@ static int sg_set_reserved_size(struct request_queue *q, int __user *p)
 
         if (size < 0)
                 return -EINVAL;
-        if (size > (queue_max_sectors(q) << 9))
-                size = queue_max_sectors(q) << 9;
 
-        q->sg_reserved_size = size;
+        q->sg_reserved_size = min(size, max_sectors_bytes(q));
         return 0;
 }