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 <computersforpe...@gmail.com> --- You can find the initial bug report / patch here: http://article.gmane.org/gmane.linux.kernel/2028927 https://lkml.org/lkml/2015/8/28/594 Changes since RFC: * create new non-UAPI header, instead of cluttering the UAPI header with compat stuff * remove mention of "same bug in block/", since block/ solves this problem already, just in a slightly different way drivers/mtd/mtdchar.c | 42 +++++++++++++++++++++++++++++++++--------- include/linux/blkpg.h | 21 +++++++++++++++++++++ include/uapi/linux/blkpg.h | 6 +++--- 3 files changed, 57 insertions(+), 12 deletions(-) create mode 100644 include/linux/blkpg.h diff --git a/drivers/mtd/mtdchar.c b/drivers/mtd/mtdchar.c index 55fa27ecf4e1..bf966be09e79 100644 --- a/drivers/mtd/mtdchar.c +++ b/drivers/mtd/mtdchar.c @@ -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 arg; + struct blkpg_ioctl_arg a; + + if (copy_from_user(&arg, uarg, sizeof(arg))) { + ret = -EFAULT; + break; + } + + memset(&a, 0, sizeof(a)); + a.op = arg.op; + a.flags = arg.flags; + a.datalen = arg.datalen; + a.data = compat_ptr(arg.data); + + ret = mtdchar_blkpg_ioctl(mtd, &a); + break; + } + default: ret = mtdchar_ioctl(file, cmd, (unsigned long)argp); } diff --git a/include/linux/blkpg.h b/include/linux/blkpg.h new file mode 100644 index 000000000000..bef124fde61e --- /dev/null +++ b/include/linux/blkpg.h @@ -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 */ diff --git a/include/uapi/linux/blkpg.h b/include/uapi/linux/blkpg.h index a8519446c111..63739a035085 100644 --- a/include/uapi/linux/blkpg.h +++ b/include/uapi/linux/blkpg.h @@ -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 */ -- 2.6.0.rc0.131.gf624c3d -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
