[PATCH v6 14/43] compat_ioctl: move tape handling into drivers

From: Arnd Bergmann
Date: Wed Oct 09 2019 - 15:13:34 EST

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MTIOCPOS and MTIOCGET are incompatible between 32-bit and 64-bit user
space, and traditionally have been translated in fs/compat_ioctl.c.

To get rid of that translation handler, move a corresponding
implementation into each of the four drivers implementing those commands.

The interesting part of that is now in a new linux/mtio.h header that
wraps the existing uapi/linux/mtio.h header and provides an abstraction
to let drivers handle both cases easily. Using an in_compat_syscall()
check, the caller does not have to keep track of whether this was
called through .unlocked_ioctl() or .compat_ioctl().

Acked-by: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
Cc: "Kai MÃkisara" <Kai.Makisara@xxxxxxxxxxx>
Cc: linux-scsi@xxxxxxxxxxxxxxx
Cc: "James E.J. Bottomley" <jejb@xxxxxxxxxxxxx>
Cc: "Martin K. Petersen" <martin.petersen@xxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
drivers/ide/ide-tape.c | 27 ++++++++++---
drivers/s390/char/tape_char.c | 41 +++++++-------------
drivers/scsi/st.c | 28 +++++++++-----
fs/compat_ioctl.c | 73 -----------------------------------
include/linux/mtio.h | 60 ++++++++++++++++++++++++++++
5 files changed, 114 insertions(+), 115 deletions(-)
create mode 100644 include/linux/mtio.h

diff --git a/drivers/ide/ide-tape.c b/drivers/ide/ide-tape.c
index db1a65f4b490..3e7482695f77 100644
--- a/drivers/ide/ide-tape.c
+++ b/drivers/ide/ide-tape.c
@@ -19,6 +19,7 @@

#define IDETAPE_VERSION "1.20"

+#include <linux/compat.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/string.h>
@@ -1407,14 +1408,10 @@ static long do_idetape_chrdev_ioctl(struct file *file,
if (tape->drv_write_prot)
mtget.mt_gstat |= GMT_WR_PROT(0xffffffff);

- if (copy_to_user(argp, &mtget, sizeof(struct mtget)))
- return -EFAULT;
- return 0;
+ return put_user_mtget(argp, &mtget);
case MTIOCPOS:
mtpos.mt_blkno = position / tape->user_bs_factor - block_offset;
- if (copy_to_user(argp, &mtpos, sizeof(struct mtpos)))
- return -EFAULT;
- return 0;
+ return put_user_mtpos(argp, &mtpos);
default:
if (tape->chrdev_dir == IDETAPE_DIR_READ)
ide_tape_discard_merge_buffer(drive, 1);
@@ -1432,6 +1429,22 @@ static long idetape_chrdev_ioctl(struct file *file,
return ret;
}

+static long idetape_chrdev_compat_ioctl(struct file *file,
+ unsigned int cmd, unsigned long arg)
+{
+ long ret;
+
+ if (cmd == MTIOCPOS32)
+ cmd = MTIOCPOS;
+ else if (cmd == MTIOCGET32)
+ cmd = MTIOCGET;
+
+ mutex_lock(&ide_tape_mutex);
+ ret = do_idetape_chrdev_ioctl(file, cmd, arg);
+ mutex_unlock(&ide_tape_mutex);
+ return ret;
+}
+
/*
* Do a mode sense page 0 with block descriptor and if it succeeds set the tape
* block size with the reported value.
@@ -1886,6 +1899,8 @@ static const struct file_operations idetape_fops = {
.read = idetape_chrdev_read,
.write = idetape_chrdev_write,
.unlocked_ioctl = idetape_chrdev_ioctl,
+ .compat_ioctl = IS_ENABLED(CONFIG_COMPAT) ?
+ idetape_chrdev_compat_ioctl : NULL,
.open = idetape_chrdev_open,
.release = idetape_chrdev_release,
.llseek = noop_llseek,
diff --git a/drivers/s390/char/tape_char.c b/drivers/s390/char/tape_char.c
index ea4253939555..8abb42923307 100644
--- a/drivers/s390/char/tape_char.c
+++ b/drivers/s390/char/tape_char.c
@@ -341,14 +341,14 @@ tapechar_release(struct inode *inode, struct file *filp)
*/
static int
__tapechar_ioctl(struct tape_device *device,
- unsigned int no, unsigned long data)
+ unsigned int no, void __user *data)
{
int rc;

if (no == MTIOCTOP) {
struct mtop op;

- if (copy_from_user(&op, (char __user *) data, sizeof(op)) != 0)
+ if (copy_from_user(&op, data, sizeof(op)) != 0)
return -EFAULT;
if (op.mt_count < 0)
return -EINVAL;
@@ -392,9 +392,7 @@ __tapechar_ioctl(struct tape_device *device,
if (rc < 0)
return rc;
pos.mt_blkno = rc;
- if (copy_to_user((char __user *) data, &pos, sizeof(pos)) != 0)
- return -EFAULT;
- return 0;
+ return put_user_mtpos(data, &pos);
}
if (no == MTIOCGET) {
/* MTIOCGET: query the tape drive status. */
@@ -424,15 +422,12 @@ __tapechar_ioctl(struct tape_device *device,
get.mt_blkno = rc;
}

- if (copy_to_user((char __user *) data, &get, sizeof(get)) != 0)
- return -EFAULT;
-
- return 0;
+ return put_user_mtget(data, &get);
}
/* Try the discipline ioctl function. */
if (device->discipline->ioctl_fn == NULL)
return -EINVAL;
- return device->discipline->ioctl_fn(device, no, data);
+ return device->discipline->ioctl_fn(device, no, (unsigned long)data);
}

static long
@@ -445,7 +440,7 @@ tapechar_ioctl(struct file *filp, unsigned int no, unsigned long data)

device = (struct tape_device *) filp->private_data;
mutex_lock(&device->mutex);
- rc = __tapechar_ioctl(device, no, data);
+ rc = __tapechar_ioctl(device, no, (void __user *)data);
mutex_unlock(&device->mutex);
return rc;
}
@@ -455,23 +450,17 @@ static long
tapechar_compat_ioctl(struct file *filp, unsigned int no, unsigned long data)
{
struct tape_device *device = filp->private_data;
- int rval = -ENOIOCTLCMD;
- unsigned long argp;
+ long rc;

- /* The 'arg' argument of any ioctl function may only be used for
- * pointers because of the compat pointer conversion.
- * Consider this when adding new ioctls.
- */
- argp = (unsigned long) compat_ptr(data);
- if (device->discipline->ioctl_fn) {
- mutex_lock(&device->mutex);
- rval = device->discipline->ioctl_fn(device, no, argp);
- mutex_unlock(&device->mutex);
- if (rval == -EINVAL)
- rval = -ENOIOCTLCMD;
- }
+ if (no == MTIOCPOS32)
+ no = MTIOCPOS;
+ else if (no == MTIOCGET32)
+ no = MTIOCGET;

- return rval;
+ mutex_lock(&device->mutex);
+ rc = __tapechar_ioctl(device, no, compat_ptr(data));
+ mutex_unlock(&device->mutex);
+ return rc;
}
#endif /* CONFIG_COMPAT */

diff --git a/drivers/scsi/st.c b/drivers/scsi/st.c
index e3266a64a477..9e3fff2de83e 100644
--- a/drivers/scsi/st.c
+++ b/drivers/scsi/st.c
@@ -22,6 +22,7 @@ static const char *verstr = "20160209";

#include <linux/module.h>

+#include <linux/compat.h>
#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/sched/signal.h>
@@ -3800,14 +3801,11 @@ static long st_ioctl(struct file *file, unsigned int cmd_in, unsigned long arg)
if (STp->cleaning_req)
mt_status.mt_gstat |= GMT_CLN(0xffffffff);

- i = copy_to_user(p, &mt_status, sizeof(struct mtget));
- if (i) {
- retval = (-EFAULT);
+ retval = put_user_mtget(p, &mt_status);
+ if (retval)
goto out;
- }

STp->recover_reg = 0; /* Clear after read */
- retval = 0;
goto out;
} /* End of MTIOCGET */
if (cmd_type == _IOC_TYPE(MTIOCPOS) && cmd_nr == _IOC_NR(MTIOCPOS)) {
@@ -3821,9 +3819,7 @@ static long st_ioctl(struct file *file, unsigned int cmd_in, unsigned long arg)
goto out;
}
mt_pos.mt_blkno = blk;
- i = copy_to_user(p, &mt_pos, sizeof(struct mtpos));
- if (i)
- retval = (-EFAULT);
+ retval = put_user_mtpos(p, &mt_pos);
goto out;
}
mutex_unlock(&STp->lock);
@@ -3857,14 +3853,26 @@ static long st_ioctl(struct file *file, unsigned int cmd_in, unsigned long arg)
}

#ifdef CONFIG_COMPAT
-static long st_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+static long st_compat_ioctl(struct file *file, unsigned int cmd_in, unsigned long arg)
{
+ void __user *p = compat_ptr(arg);
struct scsi_tape *STp = file->private_data;
struct scsi_device *sdev = STp->device;
int ret = -ENOIOCTLCMD;
+
+ /* argument conversion is handled using put_user_mtpos/put_user_mtget */
+ switch (cmd_in) {
+ case MTIOCTOP:
+ return st_ioctl(file, MTIOCTOP, (unsigned long)p);
+ case MTIOCPOS32:
+ return st_ioctl(file, MTIOCPOS, (unsigned long)p);
+ case MTIOCGET32:
+ return st_ioctl(file, MTIOCGET, (unsigned long)p);
+ }
+
if (sdev->host->hostt->compat_ioctl) {

- ret = sdev->host->hostt->compat_ioctl(sdev, cmd, (void __user *)arg);
+ ret = sdev->host->hostt->compat_ioctl(sdev, cmd_in, (void __user *)arg);

}
return ret;
diff --git a/fs/compat_ioctl.c b/fs/compat_ioctl.c
index 47da220f95b1..b65eef3d4787 100644
--- a/fs/compat_ioctl.c
+++ b/fs/compat_ioctl.c
@@ -27,7 +27,6 @@
#include <linux/file.h>
#include <linux/ppp-ioctl.h>
#include <linux/if_pppox.h>
-#include <linux/mtio.h>
#include <linux/tty.h>
#include <linux/vt_kern.h>
#include <linux/raw.h>
@@ -361,73 +360,6 @@ static int ppp_scompress(struct file *file, unsigned int cmd,
return do_ioctl(file, PPPIOCSCOMPRESS, (unsigned long) odata);
}

-#ifdef CONFIG_BLOCK
-struct mtget32 {
- compat_long_t mt_type;
- compat_long_t mt_resid;
- compat_long_t mt_dsreg;
- compat_long_t mt_gstat;
- compat_long_t mt_erreg;
- compat_daddr_t mt_fileno;
- compat_daddr_t mt_blkno;
-};
-#define MTIOCGET32 _IOR('m', 2, struct mtget32)
-
-struct mtpos32 {
- compat_long_t mt_blkno;
-};
-#define MTIOCPOS32 _IOR('m', 3, struct mtpos32)
-
-static int mt_ioctl_trans(struct file *file,
- unsigned int cmd, void __user *argp)
-{
- /* NULL initialization to make gcc shut up */
- struct mtget __user *get = NULL;
- struct mtget32 __user *umget32;
- struct mtpos __user *pos = NULL;
- struct mtpos32 __user *upos32;
- unsigned long kcmd;
- void *karg;
- int err = 0;
-
- switch(cmd) {
- case MTIOCPOS32:
- kcmd = MTIOCPOS;
- pos = compat_alloc_user_space(sizeof(*pos));
- karg = pos;
- break;
- default: /* MTIOCGET32 */
- kcmd = MTIOCGET;
- get = compat_alloc_user_space(sizeof(*get));
- karg = get;
- break;
- }
- if (karg == NULL)
- return -EFAULT;
- err = do_ioctl(file, kcmd, (unsigned long)karg);
- if (err)
- return err;
- switch (cmd) {
- case MTIOCPOS32:
- upos32 = argp;
- err = convert_in_user(&pos->mt_blkno, &upos32->mt_blkno);
- break;
- case MTIOCGET32:
- umget32 = argp;
- err = convert_in_user(&get->mt_type, &umget32->mt_type);
- err |= convert_in_user(&get->mt_resid, &umget32->mt_resid);
- err |= convert_in_user(&get->mt_dsreg, &umget32->mt_dsreg);
- err |= convert_in_user(&get->mt_gstat, &umget32->mt_gstat);
- err |= convert_in_user(&get->mt_erreg, &umget32->mt_erreg);
- err |= convert_in_user(&get->mt_fileno, &umget32->mt_fileno);
- err |= convert_in_user(&get->mt_blkno, &umget32->mt_blkno);
- break;
- }
- return err ? -EFAULT: 0;
-}
-
-#endif /* CONFIG_BLOCK */
-
/* Bluetooth ioctls */
#define HCIUARTSETPROTO _IOW('U', 200, int)
#define HCIUARTGETPROTO _IOR('U', 201, int)
@@ -479,8 +411,6 @@ IGNORE_IOCTL(VT_GETMODE)
*/
COMPATIBLE_IOCTL(_IOR('p', 20, int[7])) /* RTCGET */
COMPATIBLE_IOCTL(_IOW('p', 21, int[7])) /* RTCSET */
-/* Little m */
-COMPATIBLE_IOCTL(MTIOCTOP)
#ifdef CONFIG_BLOCK
/* md calls this on random blockdevs */
IGNORE_IOCTL(RAID_VERSION)
@@ -846,9 +776,6 @@ static long do_ioctl_trans(unsigned int cmd,
return sg_ioctl_trans(file, cmd, argp);
case SG_GET_REQUEST_TABLE:
return sg_grt_trans(file, cmd, argp);
- case MTIOCGET32:
- case MTIOCPOS32:
- return mt_ioctl_trans(file, cmd, argp);
#endif
}

diff --git a/include/linux/mtio.h b/include/linux/mtio.h
new file mode 100644
index 000000000000..67d03156f2c2
--- /dev/null
+++ b/include/linux/mtio.h
@@ -0,0 +1,60 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_MTIO_COMPAT_H
+#define _LINUX_MTIO_COMPAT_H
+
+#include <linux/compat.h>
+#include <uapi/linux/mtio.h>
+#include <linux/uaccess.h>
+
+/*
+ * helper functions for implementing compat ioctls on the four tape
+ * drivers: we define the 32-bit layout of each incompatible structure,
+ * plus a wrapper function to copy it to user space in either format.
+ */
+
+struct mtget32 {
+ s32 mt_type;
+ s32 mt_resid;
+ s32 mt_dsreg;
+ s32 mt_gstat;
+ s32 mt_erreg;
+ s32 mt_fileno;
+ s32 mt_blkno;
+};
+#define MTIOCGET32 _IOR('m', 2, struct mtget32)
+
+struct mtpos32 {
+ s32 mt_blkno;
+};
+#define MTIOCPOS32 _IOR('m', 3, struct mtpos32)
+
+static inline int put_user_mtget(void __user *u, struct mtget *k)
+{
+ struct mtget32 k32 = {
+ .mt_type = k->mt_type,
+ .mt_resid = k->mt_resid,
+ .mt_dsreg = k->mt_dsreg,
+ .mt_gstat = k->mt_gstat,
+ .mt_erreg = k->mt_erreg,
+ .mt_fileno = k->mt_fileno,
+ .mt_blkno = k->mt_blkno,
+ };
+ int ret;
+
+ if (in_compat_syscall())
+ ret = copy_to_user(u, &k32, sizeof(k32));
+ else
+ ret = copy_to_user(u, k, sizeof(*k));
+
+ return ret ? -EFAULT : 0;
+}
+
+static inline int put_user_mtpos(void __user *u, struct mtpos *k)
+{
+ if (in_compat_syscall())
+ return put_user(k->mt_blkno, (u32 __user *)u);
+ else
+ return put_user(k->mt_blkno, (long __user *)u);
+}
+
+#endif
--
2.20.0

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