compat_ioctl: reimplement SG_IO handling

There are two code locations that implement the SG_IO ioctl: the old
sg.c driver, and the generic scsi_ioctl helper that is in turn used by
multiple drivers.

To eradicate the old compat_ioctl conversion handler for the SG_IO
command, I implement a readable pair of put_sg_io_hdr() /get_sg_io_hdr()
helper functions that can be used for both compat and native mode,
and then I call this from both drivers.

For the iovec handling, there is already a compat_import_iovec() function
that can simply be called in place of import_iovec().

To avoid having to pass the compat/native state through multiple
indirections, I mark the SG_IO command itself as compatible in
fs/compat_ioctl.c and use in_compat_syscall() to figure out where
we are called from.

As a side-effect of this, the sg.c driver now also accepts the 32-bit
sg_io_hdr format in compat mode using the read/write interface, not
just ioctl. This should improve compatiblity with old 32-bit binaries,
but it would break if any application intentionally passes the 64-bit
data structure in compat mode here.

Steffen Maier helped debug an issue in an earlier version of this patch.

Cc: Steffen Maier <maier@linux.ibm.com>
Cc: linux-scsi@vger.kernel.org
Cc: Doug Gilbert <dgilbert@interlog.com>
Cc: "James E.J. Bottomley" <jejb@linux.ibm.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

1 files changed, 128 insertions, 4 deletions

diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c
index f5e0ad65e86a..650bade5ea5a 100644
--- a/block/scsi_ioctl.c
+++ b/block/scsi_ioctl.c
@@ -2,6 +2,7 @@
 /*
  * Copyright (C) 2001 Jens Axboe <axboe@suse.de>
  */
+#include <linux/compat.h>
 #include <linux/kernel.h>
 #include <linux/errno.h>
 #include <linux/string.h>
@@ -327,7 +328,14 @@ static int sg_io(struct request_queue *q, struct gendisk *bd_disk,
 		struct iov_iter i;
 		struct iovec *iov = NULL;
 
-		ret = import_iovec(rq_data_dir(rq),
+#ifdef CONFIG_COMPAT
+		if (in_compat_syscall())
+			ret = compat_import_iovec(rq_data_dir(rq),
+				   hdr->dxferp, hdr->iovec_count,
+				   0, &iov, &i);
+		else
+#endif
+			ret = import_iovec(rq_data_dir(rq),
 				   hdr->dxferp, hdr->iovec_count,
 				   0, &iov, &i);
 		if (ret < 0)
@@ -542,6 +550,122 @@ static inline int blk_send_start_stop(struct request_queue *q,
 	return __blk_send_generic(q, bd_disk, GPCMD_START_STOP_UNIT, data);
 }
 
+#ifdef CONFIG_COMPAT
+struct compat_sg_io_hdr {
+	compat_int_t interface_id;	/* [i] 'S' for SCSI generic (required) */
+	compat_int_t dxfer_direction;	/* [i] data transfer direction  */
+	unsigned char cmd_len;		/* [i] SCSI command length ( <= 16 bytes) */
+	unsigned char mx_sb_len;	/* [i] max length to write to sbp */
+	unsigned short iovec_count;	/* [i] 0 implies no scatter gather */
+	compat_uint_t dxfer_len;	/* [i] byte count of data transfer */
+	compat_uint_t dxferp;		/* [i], [*io] points to data transfer memory
+						or scatter gather list */
+	compat_uptr_t cmdp;		/* [i], [*i] points to command to perform */
+	compat_uptr_t sbp;		/* [i], [*o] points to sense_buffer memory */
+	compat_uint_t timeout;		/* [i] MAX_UINT->no timeout (unit: millisec) */
+	compat_uint_t flags;		/* [i] 0 -> default, see SG_FLAG... */
+	compat_int_t pack_id;		/* [i->o] unused internally (normally) */
+	compat_uptr_t usr_ptr;		/* [i->o] unused internally */
+	unsigned char status;		/* [o] scsi status */
+	unsigned char masked_status;	/* [o] shifted, masked scsi status */
+	unsigned char msg_status;	/* [o] messaging level data (optional) */
+	unsigned char sb_len_wr;	/* [o] byte count actually written to sbp */
+	unsigned short host_status;	/* [o] errors from host adapter */
+	unsigned short driver_status;	/* [o] errors from software driver */
+	compat_int_t resid;		/* [o] dxfer_len - actual_transferred */
+	compat_uint_t duration;		/* [o] time taken by cmd (unit: millisec) */
+	compat_uint_t info;		/* [o] auxiliary information */
+};
+#endif
+
+int put_sg_io_hdr(const struct sg_io_hdr *hdr, void __user *argp)
+{
+#ifdef CONFIG_COMPAT
+	if (in_compat_syscall()) {
+		struct compat_sg_io_hdr hdr32 =  {
+			.interface_id	 = hdr->interface_id,
+			.dxfer_direction = hdr->dxfer_direction,
+			.cmd_len	 = hdr->cmd_len,
+			.mx_sb_len	 = hdr->mx_sb_len,
+			.iovec_count	 = hdr->iovec_count,
+			.dxfer_len	 = hdr->dxfer_len,
+			.dxferp		 = (uintptr_t)hdr->dxferp,
+			.cmdp		 = (uintptr_t)hdr->cmdp,
+			.sbp		 = (uintptr_t)hdr->sbp,
+			.timeout	 = hdr->timeout,
+			.flags		 = hdr->flags,
+			.pack_id	 = hdr->pack_id,
+			.usr_ptr	 = (uintptr_t)hdr->usr_ptr,
+			.status		 = hdr->status,
+			.masked_status	 = hdr->masked_status,
+			.msg_status	 = hdr->msg_status,
+			.sb_len_wr	 = hdr->sb_len_wr,
+			.host_status	 = hdr->host_status,
+			.driver_status	 = hdr->driver_status,
+			.resid		 = hdr->resid,
+			.duration	 = hdr->duration,
+			.info		 = hdr->info,
+		};
+
+		if (copy_to_user(argp, &hdr32, sizeof(hdr32)))
+			return -EFAULT;
+
+		return 0;
+	}
+#endif
+
+	if (copy_to_user(argp, hdr, sizeof(*hdr)))
+		return -EFAULT;
+
+	return 0;
+}
+EXPORT_SYMBOL(put_sg_io_hdr);
+
+int get_sg_io_hdr(struct sg_io_hdr *hdr, const void __user *argp)
+{
+#ifdef CONFIG_COMPAT
+	struct compat_sg_io_hdr hdr32;
+
+	if (in_compat_syscall()) {
+		if (copy_from_user(&hdr32, argp, sizeof(hdr32)))
+			return -EFAULT;
+
+		*hdr = (struct sg_io_hdr) {
+			.interface_id	 = hdr32.interface_id,
+			.dxfer_direction = hdr32.dxfer_direction,
+			.cmd_len	 = hdr32.cmd_len,
+			.mx_sb_len	 = hdr32.mx_sb_len,
+			.iovec_count	 = hdr32.iovec_count,
+			.dxfer_len	 = hdr32.dxfer_len,
+			.dxferp		 = compat_ptr(hdr32.dxferp),
+			.cmdp		 = compat_ptr(hdr32.cmdp),
+			.sbp		 = compat_ptr(hdr32.sbp),
+			.timeout	 = hdr32.timeout,
+			.flags		 = hdr32.flags,
+			.pack_id	 = hdr32.pack_id,
+			.usr_ptr	 = compat_ptr(hdr32.usr_ptr),
+			.status		 = hdr32.status,
+			.masked_status	 = hdr32.masked_status,
+			.msg_status	 = hdr32.msg_status,
+			.sb_len_wr	 = hdr32.sb_len_wr,
+			.host_status	 = hdr32.host_status,
+			.driver_status	 = hdr32.driver_status,
+			.resid		 = hdr32.resid,
+			.duration	 = hdr32.duration,
+			.info		 = hdr32.info,
+		};
+
+		return 0;
+	}
+#endif
+
+	if (copy_from_user(hdr, argp, sizeof(*hdr)))
+		return -EFAULT;
+
+	return 0;
+}
+EXPORT_SYMBOL(get_sg_io_hdr);
+
 int scsi_cmd_ioctl(struct request_queue *q, struct gendisk *bd_disk, fmode_t mode,
 		   unsigned int cmd, void __user *arg)
 {
@@ -581,14 +705,14 @@ int scsi_cmd_ioctl(struct request_queue *q, struct gendisk *bd_disk, fmode_t mod
 		case SG_IO: {
 			struct sg_io_hdr hdr;
 
-			err = -EFAULT;
-			if (copy_from_user(&hdr, arg, sizeof(hdr)))
+			err = get_sg_io_hdr(&hdr, arg);
+			if (err)
 				break;
 			err = sg_io(q, bd_disk, &hdr, mode);
 			if (err == -EFAULT)
 				break;
 
-			if (copy_to_user(arg, &hdr, sizeof(hdr)))
+			if (put_sg_io_hdr(&hdr, arg))
 				err = -EFAULT;
 			break;
 		}