[Minios-devel] [UNIKRAFT PATCH 1/3] lib/nolibc/string: fix underflow in strnlen

[Yuri Volchkov <yuri.volchkov@xxxxxxxxx>]

The memchr return NULL if it did not find '\0' character. The strnlen
did not take this into account and always did subtraction to count the
string length.

Return the provided length limit if the line ending is not found
within this limit.

Signed-off-by: Yuri Volchkov <yuri.volchkov@xxxxxxxxx>
---
 lib/nolibc/string.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/nolibc/string.c b/lib/nolibc/string.c
index 6f853ba..fee2d10 100644
--- a/lib/nolibc/string.c
+++ b/lib/nolibc/string.c
@@ -132,7 +132,8 @@ size_t strlen(const char *str)
 
 size_t strnlen(const char *str, size_t len)
 {
-       return (size_t)((uintptr_t)memchr(str, '\0', len) - (uintptr_t)str);
+       const char *p = memchr(str, 0, len);
+       return p ? (size_t) (p - str) : len;
 }
 
 char *strncpy(char *dst, const char *src, size_t len)
-- 
2.19.2


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