[musl] [PATCH v2] mman: correct length check in __shm_mapname

[<lihua.zhao.cn@windriver.com>]

From: Lihua Zhao <lihua.zhao.cn@windriver.com>

account for leading slashes when comparing against NAME_MAX.

Signed-off-by: Lihua Zhao <lihua.zhao.cn@windriver.com>
---
According to https://pubs.opengroup.org/onlinepubs/9799919799/:

leading <slash> character in name is implementation-defined, and that the length limits for the name argument are implementation-defined and need not be the same as the pathname limits {PATH_MAX} and {NAME_MAX}.

Although it is implementation-defined, glibc obviously calculates the lead slash.

 src/mman/shm_open.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/mman/shm_open.c b/src/mman/shm_open.c
index 79784bd3..07dbeb96 100644
--- a/src/mman/shm_open.c
+++ b/src/mman/shm_open.c
@@ -8,19 +8,19 @@

 char *__shm_mapname(const char *name, char *buf)
 {
-	char *p;
-	while (*name == '/') name++;
-	if (*(p = __strchrnul(name, '/')) || p==name ||
-	    (p-name <= 2 && name[0]=='.' && p[-1]=='.')) {
+	const char *s=name, *e;
+	while (*s == '/') s++;
+	if (*(e = __strchrnul(s, '/')) || e==s ||
+	    (e-s <= 2 && s[0]=='.' && e[-1]=='.')) {
 		errno = EINVAL;
 		return 0;
 	}
-	if (p-name > NAME_MAX) {
+	if (e-name > NAME_MAX) {
 		errno = ENAMETOOLONG;
 		return 0;
 	}
 	memcpy(buf, "/dev/shm/", 9);
-	memcpy(buf+9, name, p-name+1);
+	memcpy(buf+9, s, e-s+1);
 	return buf;
 }

--
2.34.1