[MTD] mtdchar.c: Fix regression in MEMGETREGIONINFO ioctl()

The MEMGETREGIONINFO ioctl() in mtdchar.c was clobbering user memory by
overwriting more than intended, due the size of struct mtd_erase_region_info
changing in commit 0ecbc81adfcb9f15f86b05ff576b342ce81bbef8 ('Support
for auto locking flash on power up').

Fix avoids this by copying struct members one by one with put_user(), as there
is no longer a convenient struct to use the size of as the length argument to
copy_to_user().

Signed-off-by: Zev Weiss <zevweiss@gmail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

1 files changed, 10 insertions, 6 deletions

diff --git a/drivers/mtd/mtdchar.c b/drivers/mtd/mtdchar.c
index d2f331876e4c..e00d424e6575 100644
--- a/drivers/mtd/mtdchar.c
+++ b/drivers/mtd/mtdchar.c
@@ -410,16 +410,20 @@ static int mtd_ioctl(struct inode *inode, struct file *file,
 
         case MEMGETREGIONINFO:
         {
-                struct region_info_user ur;
+                uint32_t ur_idx;
+                struct mtd_erase_region_info *kr;
+                struct region_info_user *ur = (struct region_info_user *) argp;
 
-                if (copy_from_user(&ur, argp, sizeof(struct region_info_user)))
+                if (get_user(ur_idx, &(ur->regionindex)))
                         return -EFAULT;
 
-                if (ur.regionindex >= mtd->numeraseregions)
-                        return -EINVAL;
-                if (copy_to_user(argp, &(mtd->eraseregions[ur.regionindex]),
-                                sizeof(struct mtd_erase_region_info)))
+                kr = &(mtd->eraseregions[ur_idx]);
+
+                if (put_user(kr->offset, &(ur->offset))
+                    || put_user(kr->erasesize, &(ur->erasesize))
+                    || put_user(kr->numblocks, &(ur->numblocks)))
                         return -EFAULT;
+
                 break;
         }