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mtd: provide proper 32/64-bit compat_ioctl() support for BLKPG

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After a bit of poking around wondering why my 32-bit user-space can't
seem to send a proper ioctl(BLKPG) to an MTD on my 64-bit kernel
(ARM64), I noticed that struct blkpg_ioctl_arg is actually pretty
unsuitable for use in the ioctl() ABI, due to its use of raw pointers,
and its lack of alignment/packing restrictions (32-bit arch'es tend to
pack the 4 fields into 4 32-bit words, whereas 64-bit arch'es would add
padding after the third int, and make this 6 32-bit words).

Anyway, this means BLKPG deserves some special compat_ioctl handling. Do
the conversion in a small shim for MTD.

block/compat_ioctl.c already has compat support for the block subsystem,
but it does so by a re-marshalling data to/from user-space (see
compat_blkpg_ioctl()). Personally, I think this approach is cleaner.

Tested only on MTD, with an ARM32 user space on an ARM64 kernel.

Signed-off-by: Brian Norris <computersforpeace@gmail.com>
This commit is contained in:
Brian Norris 2015-09-21 13:26:59 -07:00
parent 4404bd742d
commit 53bb724f94
3 changed files with 57 additions and 12 deletions
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42
drivers/mtd/mtdchar.c
View File

@ -498,21 +498,17 @@ static int shrink_ecclayout(const struct nand_ecclayout *from,
}
static int mtdchar_blkpg_ioctl(struct mtd_info *mtd,
struct blkpg_ioctl_arg __user *arg)
struct blkpg_ioctl_arg *arg)
{
struct blkpg_ioctl_arg a;
struct blkpg_partition p;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
if (copy_from_user(&a, arg, sizeof(struct blkpg_ioctl_arg)))
if (copy_from_user(&p, arg->data, sizeof(p)))
return -EFAULT;
if (copy_from_user(&p, a.data, sizeof(struct blkpg_partition)))
return -EFAULT;
switch (a.op) {
switch (arg->op) {
case BLKPG_ADD_PARTITION:
/* Only master mtd device must be used to add partitions */
@ -966,8 +962,13 @@ static int mtdchar_ioctl(struct file *file, u_int cmd, u_long arg)
case BLKPG:
{
ret = mtdchar_blkpg_ioctl(mtd,
(struct blkpg_ioctl_arg __user *)arg);
struct blkpg_ioctl_arg __user *blk_arg = argp;
struct blkpg_ioctl_arg a;
if (copy_from_user(&a, blk_arg, sizeof(a)))
ret = -EFAULT;
else
ret = mtdchar_blkpg_ioctl(mtd, &a);
break;
}
@ -1046,6 +1047,29 @@ static long mtdchar_compat_ioctl(struct file *file, unsigned int cmd,
&buf_user->start);
break;
}
case BLKPG:
{
/* Convert from blkpg_compat_ioctl_arg to blkpg_ioctl_arg */
struct blkpg_compat_ioctl_arg __user *uarg = argp;
struct blkpg_compat_ioctl_arg compat_arg;
struct blkpg_ioctl_arg a;
if (copy_from_user(&compat_arg, uarg, sizeof(compat_arg))) {
ret = -EFAULT;
break;
}
memset(&a, 0, sizeof(a));
a.op = compat_arg.op;
a.flags = compat_arg.flags;
a.datalen = compat_arg.datalen;
a.data = compat_ptr(compat_arg.data);
ret = mtdchar_blkpg_ioctl(mtd, &a);
break;
}
default:
ret = mtdchar_ioctl(file, cmd, (unsigned long)argp);
}

21
include/linux/blkpg.h Normal file
View File

@ -0,0 +1,21 @@
#ifndef _LINUX_BLKPG_H
#define _LINUX_BLKPG_H
/*
* Partition table and disk geometry handling
*/
#include <linux/compat.h>
#include <uapi/linux/blkpg.h>
#ifdef CONFIG_COMPAT
/* For 32-bit/64-bit compatibility of struct blkpg_ioctl_arg */
struct blkpg_compat_ioctl_arg {
compat_int_t op;
compat_int_t flags;
compat_int_t datalen;
compat_uptr_t data;
};
#endif
#endif /* _LINUX_BLKPG_H */

6
include/uapi/linux/blkpg.h
View File

@ -1,5 +1,5 @@
#ifndef _LINUX_BLKPG_H
#define _LINUX_BLKPG_H
#ifndef _UAPI__LINUX_BLKPG_H
#define _UAPI__LINUX_BLKPG_H
/*
* Partition table and disk geometry handling
@ -56,4 +56,4 @@ struct blkpg_partition {
char volname[BLKPG_VOLNAMELTH]; /* volume label */
};
#endif /* _LINUX_BLKPG_H */
#endif /* _UAPI__LINUX_BLKPG_H */