Commit 53bb724f authored by Brian Norris's avatar Brian Norris
Browse files

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



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: default avatarBrian Norris <computersforpeace@gmail.com>
parent 4404bd74

drivers/mtd/mtdchar.c

+33 −9
Original line number Diff line number Diff line
@@ -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)))

		return -EFAULT;



	if (copy_from_user(&p, a.data, sizeof(struct blkpg_partition)))

	if (copy_from_user(&p, arg->data, sizeof(p)))

		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);

	}

include/linux/blkpg.h

0 → 100644
+21 −0
Original line number Diff line number Diff line 
#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 */

include/uapi/linux/blkpg.h

+3 −3
Original line number Diff line number Diff line 
#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 */

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