Commit 630fdd59 authored by Kees Cook's avatar Kees Cook
Browse files

seq_file: seq_show_option_n() is used for precise sizes 



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.

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>
Reviewed-by: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20230726215957.never.619-kees@kernel.org


Signed-off-by: default avatarKees Cook <keescook@chromium.org>
parent 8453e792

include/linux/seq_file.h

+4 −3
Original line number Diff line number Diff line
@@ -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);		\

}