allow userspace to modify scsi command filter on per device basis

This patch exports the per-gendisk command filter to user space through
sysfs, so it can be changed by the system administrator.
All users of the old cmd filter have been converted to use the new one.

Original patch from Peter Jones.

Signed-off-by: Adel Gadllah <adel.gadllah@gmail.com>
Signed-off-by: Peter Jones <pjones@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

block/Makefile

@@ -4,7 +4,8 @@
 
 obj-$(CONFIG_BLOCK) := elevator.o blk-core.o blk-tag.o blk-sysfs.o \
 			blk-barrier.o blk-settings.o blk-ioc.o blk-map.o \
-			blk-exec.o blk-merge.o ioctl.o genhd.o scsi_ioctl.o
+			blk-exec.o blk-merge.o ioctl.o genhd.o scsi_ioctl.o \
+			cmd-filter.o
 
 obj-$(CONFIG_BLK_DEV_BSG)	+= bsg.o
 obj-$(CONFIG_IOSCHED_NOOP)	+= noop-iosched.o

block/bsg.c

@@ -44,11 +44,12 @@ struct bsg_device {
 	char name[BUS_ID_SIZE];
 	int max_queue;
 	unsigned long flags;
+	struct blk_scsi_cmd_filter *cmd_filter;
+	mode_t *f_mode;
 };
 
 enum {
 	BSG_F_BLOCK		= 1,
-	BSG_F_WRITE_PERM	= 2,
 };
 
 #define BSG_DEFAULT_CMDS	64
@@ -172,7 +173,7 @@ static int bsg_io_schedule(struct bsg_device *bd)
 }
 
 static int blk_fill_sgv4_hdr_rq(struct request_queue *q, struct request *rq,
-				struct sg_io_v4 *hdr, int has_write_perm)
+				struct sg_io_v4 *hdr, struct bsg_device *bd)
 {
 	if (hdr->request_len > BLK_MAX_CDB) {
 		rq->cmd = kzalloc(hdr->request_len, GFP_KERNEL);
@@ -185,7 +186,8 @@ static int blk_fill_sgv4_hdr_rq(struct request_queue *q, struct request *rq,
 		return -EFAULT;
 
 	if (hdr->subprotocol == BSG_SUB_PROTOCOL_SCSI_CMD) {
-		if (blk_verify_command(rq->cmd, has_write_perm))
+		if (blk_cmd_filter_verify_command(bd->cmd_filter, rq->cmd,
+						 bd->f_mode))
 			return -EPERM;
 	} else if (!capable(CAP_SYS_RAWIO))
 		return -EPERM;
@@ -263,8 +265,7 @@ bsg_map_hdr(struct bsg_device *bd, struct sg_io_v4 *hdr)
 	rq = blk_get_request(q, rw, GFP_KERNEL);
 	if (!rq)
 		return ERR_PTR(-ENOMEM);
-	ret = blk_fill_sgv4_hdr_rq(q, rq, hdr, test_bit(BSG_F_WRITE_PERM,
-						       &bd->flags));
+	ret = blk_fill_sgv4_hdr_rq(q, rq, hdr, bd);
 	if (ret)
 		goto out;
 
@@ -566,12 +567,23 @@ static inline void bsg_set_block(struct bsg_device *bd, struct file *file)
 		set_bit(BSG_F_BLOCK, &bd->flags);
 }
 
-static inline void bsg_set_write_perm(struct bsg_device *bd, struct file *file)
+static void bsg_set_cmd_filter(struct bsg_device *bd,
+			   struct file *file)
 {
-	if (file->f_mode & FMODE_WRITE)
-		set_bit(BSG_F_WRITE_PERM, &bd->flags);
-	else
-		clear_bit(BSG_F_WRITE_PERM, &bd->flags);
+	struct inode *inode;
+	struct gendisk *disk;
+
+	if (!file)
+		return;
+
+	inode = file->f_dentry->d_inode;
+	if (!inode)
+		return;
+
+	disk = inode->i_bdev->bd_disk;
+
+	bd->cmd_filter = &disk->cmd_filter;
+	bd->f_mode = &file->f_mode;
 }
 
 /*
@@ -595,6 +607,8 @@ bsg_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 	dprintk("%s: read %Zd bytes\n", bd->name, count);
 
 	bsg_set_block(bd, file);
+	bsg_set_cmd_filter(bd, file);
+
 	bytes_read = 0;
 	ret = __bsg_read(buf, count, bd, NULL, &bytes_read);
 	*ppos = bytes_read;
@@ -668,7 +682,7 @@ bsg_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
 	dprintk("%s: write %Zd bytes\n", bd->name, count);
 
 	bsg_set_block(bd, file);
-	bsg_set_write_perm(bd, file);
+	bsg_set_cmd_filter(bd, file);
 
 	bytes_written = 0;
 	ret = __bsg_write(bd, buf, count, &bytes_written);
@@ -771,7 +785,9 @@ static struct bsg_device *bsg_add_device(struct inode *inode,
 	}
 
 	bd->queue = rq;
+
 	bsg_set_block(bd, file);
+	bsg_set_cmd_filter(bd, file);
 
 	atomic_set(&bd->ref_count, 1);
 	mutex_lock(&bsg_mutex);