Imagine you have a user controlled variable at the end of a struct which is allocated at the end of a page. The strlen() could read beyond the mapped memory and cause an oops.
Probably there are two reasons why we have never hit this condition in real life. First you would have to be really unlucky for all the variables to line up so the oops can happen. Second we don't do a lot of fuzzing with invalid strings. The strnlen() call is obviously a little bit slower than strlen() but I have tested it and I think it's probably ok. Reported-by: Vegard Nossum <[email protected]> Signed-off-by: Dan Carpenter <[email protected]> diff --git a/lib/string.c b/lib/string.c index 9b1f906..8074962 100644 --- a/lib/string.c +++ b/lib/string.c @@ -148,10 +148,10 @@ EXPORT_SYMBOL(strncpy); */ size_t strlcpy(char *dest, const char *src, size_t size) { - size_t ret = strlen(src); + size_t ret = strnlen(src, size); if (size) { - size_t len = (ret >= size) ? size - 1 : ret; + size_t len = (ret < size) ? ret : ret - 1; memcpy(dest, src, len); dest[len] = '\0'; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
