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    Subject[PATCH] [MTD] mtdchar.c: Fix regression in MEMGETREGIONINFO ioctl()
    From: Zev Weiss <zevweiss@gmail.com>

    The MEMGETREGIONINFO ioctl() in mtdchar.c was clobbering user memory by
    overwriting more than intended, due to the size of struct
    mtd_erase_region_info changing in commit
    0ecbc81adfcb9f15f86b05ff576b342ce81bbef8.

    Fix uses a member-by-member copy into a local struct region_info_user,
    which is then copy_to_user()'d (and matches the size correctly by being
    of the same type as the pointer passed in the ioctl() call).

    Signed-off-by: Zev Weiss <zevweiss@gmail.com>
    Tested-by: Zev Weiss <zevweiss@gmail.com>
    ---
    I had been having some problems with userspace memory corruption, and traced
    them to a MEMGETREGIONINFO ioctl() on an MTD device. I applied this patch and
    it seems to fix the problem, though I am not an expert and there may be a more
    correct way to go about doing this. I'm also new at submitting patches, so
    hopefully I haven't screwed up the patch-submission etiquette too
    horrifically.

    drivers/mtd/mtdchar.c | 11 +++++++++--
    1 files changed, 9 insertions(+), 2 deletions(-)

    diff --git a/drivers/mtd/mtdchar.c b/drivers/mtd/mtdchar.c
    index 13cc67a..0acb135 100644
    --- a/drivers/mtd/mtdchar.c
    +++ b/drivers/mtd/mtdchar.c
    @@ -411,14 +411,21 @@ static int mtd_ioctl(struct inode *inode, struct file *file,
    case MEMGETREGIONINFO:
    {
    struct region_info_user ur;
    + struct mtd_erase_region_info *kr;

    if (copy_from_user(&ur, argp, sizeof(struct region_info_user)))
    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.regionindex]);
    +
    + ur.offset = kr->offset;
    + ur.erasesize = kr->erasesize;
    + ur.numblocks = kr->numblocks;
    +
    + if (copy_to_user(argp, &ur, sizeof(struct region_info_user)))
    return -EFAULT;
    break;
    }

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