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SubjectRe: [PATCH] module: report -EFAULT on bytes remaining
On Wed, Sep 12, 2012 at 08:06:16AM -0700, Kees Cook wrote:
> Caught by smatch:
> kernel/module.c:2450 copy_module_from_user() warn: maybe return -EFAULT instead of the bytes remaining?
>
> Clean up the copy_from_user() call to not report a positive value.
> With this patch, init_module() will report errors from copy_from_user
> (before it would always only report -EFAULT when err != 0).
>
> Reported-by: Fengguang Wu <fengguang.wu@intel.com>
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> This change is on top of the finit_module patch series.
> ---
> kernel/module.c | 5 ++++-
> 1 files changed, 4 insertions(+), 1 deletions(-)
>
> diff --git a/kernel/module.c b/kernel/module.c
> index 0ad03c4..05b8dde 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -2441,8 +2441,11 @@ int copy_module_from_user(const void __user *umod, unsigned long len,
> return -ENOMEM;
>
> err = copy_from_user(info->hdr, umod, info->len);
> - if (err)
> + if (err) {
> + if (err > 0)
^^^^^^^^^^^
This condition is always true because copy_to/from_user() returns
the number of bytes remaining to be copied. (It never returns a
negative error code).

> + err = -EFAULT;
> goto free_hdr;
> + }

regards,
dan carpenter




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