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seq_file: seq_show_option_n() is used for precise sizes

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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: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20230726215957.never.619-kees@kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Kees Cook
2023-07-26 14:59:57 -07:00
parent 8453e7924a
commit 630fdd5929
1 changed files with 4 additions and 3 deletions
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7
include/linux/seq_file.h
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@@ -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 * 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 * @m: the seq_file handle
* @name: the mount option name * @name: the mount option name
* @value: the mount option name's value, cannot be NULL * @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 * This is a macro since this uses "length" to define the size of the
* stack buffer. * stack buffer.
*/ */
#define seq_show_option_n(m, name, value, length) { \ #define seq_show_option_n(m, name, value, length) { \
char val_buf[length + 1]; \ char val_buf[length + 1]; \
strncpy(val_buf, value, length); \ memcpy(val_buf, value, length); \
val_buf[length] = '\0'; \ val_buf[length] = '\0'; \
seq_show_option(m, name, val_buf); \ seq_show_option(m, name, val_buf); \
} }