lkml.org 
[lkml]   [2023]   [Jul]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] seq_file: seq_show_option_n() is used for precise sizes
On Wed, Jul 26, 2023 at 02:59:57PM -0700, Kees Cook wrote:
> When seq_show_option_n() is used, it is for non-string memory that
> happens to be printable bytes. As such, we must use memcpy() to copy the
> bytes and then explicitly NUL-terminate the result.

FWIW,
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Al Viro <viro@zeniv.linux.org.uk>
> Cc: Muchun Song <muchun.song@linux.dev>
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
> include/linux/seq_file.h | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h
> index bd023dd38ae6..386ab580b839 100644
> --- a/include/linux/seq_file.h
> +++ b/include/linux/seq_file.h
> @@ -249,18 +249,19 @@ static inline void seq_show_option(struct seq_file *m, const char *name,
>
> /**
> * seq_show_option_n - display mount options with appropriate escapes
> - * where @value must be a specific length.
> + * where @value must be a specific length (i.e.
> + * not NUL-terminated).
> * @m: the seq_file handle
> * @name: the mount option name
> * @value: the mount option name's value, cannot be NULL
> - * @length: the length of @value to display
> + * @length: the exact length of @value to display, must be constant expression
> *
> * This is a macro since this uses "length" to define the size of the
> * stack buffer.
> */
> #define seq_show_option_n(m, name, value, length) { \
> char val_buf[length + 1]; \
> - strncpy(val_buf, value, length); \
> + memcpy(val_buf, value, length); \
> val_buf[length] = '\0'; \
> seq_show_option(m, name, val_buf); \
> }
> --
> 2.34.1
>

--
With Best Regards,
Andy Shevchenko


\
 
 \ /
  Last update: 2023-07-27 15:03    [W:0.038 / U:0.796 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site