[PATCH 1/2] mtd: mtdchar.c silence sparse warning - Kernel

This is a discussion on [PATCH 1/2] mtd: mtdchar.c silence sparse warning - Kernel ; The copy_to_user was casting away the address space to get the offset of the length member. Use offsetof() instead and add it to the void __user *argp. drivers/mtd/mtdchar.c:527:23: warning: cast removes address space of expression drivers/mtd/mtdchar.c:527:23: warning: incorrect type in ...

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Thread: [PATCH 1/2] mtd: mtdchar.c silence sparse warning

  1. [PATCH 1/2] mtd: mtdchar.c silence sparse warning

    The copy_to_user was casting away the address space to get the offset
    of the length member. Use offsetof() instead and add it to the void __user *argp.

    drivers/mtd/mtdchar.c:527:23: warning: cast removes address space of expression
    drivers/mtd/mtdchar.c:527:23: warning: incorrect type in argument 1 (different address spaces)
    drivers/mtd/mtdchar.c:527:23: expected void [noderef] *to
    drivers/mtd/mtdchar.c:527:23: got unsigned int *

    Signed-off-by: Harvey Harrison
    ---
    drivers/mtd/mtdchar.c | 2 +-
    1 files changed, 1 insertions(+), 1 deletions(-)

    diff --git a/drivers/mtd/mtdchar.c b/drivers/mtd/mtdchar.c
    index 5d3ac51..3522d4a 100644
    --- a/drivers/mtd/mtdchar.c
    +++ b/drivers/mtd/mtdchar.c
    @@ -524,7 +524,7 @@ static int mtd_ioctl(struct inode *inode, struct file *file,
    if (ops.oobretlen > 0xFFFFFFFFU)
    ret = -EOVERFLOW;
    retlen = ops.oobretlen;
    - if (copy_to_user(&((struct mtd_oob_buf *)argp)->length,
    + if (copy_to_user(argp + offsetof(struct mtd_oob_buf, length),
    &retlen, sizeof(buf.length)))
    ret = -EFAULT;

    --
    1.5.5.1.482.g0f174


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  2. Re: [PATCH 1/2] mtd: mtdchar.c silence sparse warning

    On Wed, 14 May 2008 18:22:10 -0700 Harvey Harrison wrote:

    > The copy_to_user was casting away the address space to get the offset
    > of the length member. Use offsetof() instead and add it to the void __user *argp.
    >
    > drivers/mtd/mtdchar.c:527:23: warning: cast removes address space of expression
    > drivers/mtd/mtdchar.c:527:23: warning: incorrect type in argument 1 (different address spaces)
    > drivers/mtd/mtdchar.c:527:23: expected void [noderef] *to
    > drivers/mtd/mtdchar.c:527:23: got unsigned int *
    >
    > Signed-off-by: Harvey Harrison
    > ---
    > drivers/mtd/mtdchar.c | 2 +-
    > 1 files changed, 1 insertions(+), 1 deletions(-)
    >
    > diff --git a/drivers/mtd/mtdchar.c b/drivers/mtd/mtdchar.c
    > index 5d3ac51..3522d4a 100644
    > --- a/drivers/mtd/mtdchar.c
    > +++ b/drivers/mtd/mtdchar.c
    > @@ -524,7 +524,7 @@ static int mtd_ioctl(struct inode *inode, struct file *file,
    > if (ops.oobretlen > 0xFFFFFFFFU)
    > ret = -EOVERFLOW;
    > retlen = ops.oobretlen;
    > - if (copy_to_user(&((struct mtd_oob_buf *)argp)->length,
    > + if (copy_to_user(argp + offsetof(struct mtd_oob_buf, length),
    > &retlen, sizeof(buf.length)))
    > ret = -EFAULT;


    Cleaner would be:

    struct mtd_oob_buf __user *user_mtd_oob_buf = argp;

    if (copy_to_user(&user_mtd_oob_buf->length, ...

    ?

    (cleaner, faster and shorter would be put_user(), but that's off-topic).
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  3. Re: [PATCH 1/2] mtd: mtdchar.c silence sparse warning

    On Wed, May 14, 2008 at 06:38:37PM -0700, Andrew Morton wrote:
    > > - if (copy_to_user(&((struct mtd_oob_buf *)argp)->length,
    > > + if (copy_to_user(argp + offsetof(struct mtd_oob_buf, length),
    > > &retlen, sizeof(buf.length)))
    > > ret = -EFAULT;

    >
    > Cleaner would be:
    >
    > struct mtd_oob_buf __user *user_mtd_oob_buf = argp;
    >
    > if (copy_to_user(&user_mtd_oob_buf->length, ...


    Yup. BTW, &((type __user *)p)->field) would work just fine too, but yeah,
    local variable like that would be cleaner.
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