shared: use memdup over stdndupa

The stdndupa has a couple of gotchas: - allocates memory on stack via alloca(3)... where we pass it a user-provided string in at least one instance - it's a GNU extension missing on musl and bionic The mkdir_p() function is not a hot path, so using heap allocation is perfectly fine. Swap the stdndupa for our local helper memdup. Signed-off-by: Emil Velikov <[email protected]> Link: #92 Signed-off-by: Lucas De Marchi <[email protected]>
kmod-project · Sep 2, 2024 · b27aa3f · b27aa3f
1 parent 7a1de13
commit b27aa3f
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diff --git a/configure.ac b/configure.ac
@@ -50,10 +50,9 @@ CC_CHECK_FUNC_BUILTIN([__builtin_uaddll_overflow], [ ], [ ])
 # dietlibc doesn't have st.st_mtim struct member
 AC_CHECK_MEMBERS([struct stat.st_mtim], [], [], [#include <sys/stat.h>])
 
-# musl 1.0 and bionic 4.4 don't have strndupa
 # basename may be only available in libgen.h with the POSIX behavior,
 # not desired here
-AC_CHECK_DECLS_ONCE([[strndupa], [basename]], [], [], [[#include <string.h>]])
+AC_CHECK_DECLS_ONCE([[basename]], [], [], [[#include <string.h>]])
 
 AC_MSG_CHECKING([whether _Static_assert() is supported])
 AC_COMPILE_IFELSE(

diff --git a/shared/missing.h b/shared/missing.h
@@ -34,18 +34,6 @@ static inline int finit_module(int fd, const char *uargs, int flags)
 }
 #endif
 
-#if !HAVE_DECL_STRNDUPA
-#include <string.h>
-#define strndupa(s, n)							\
-	({								\
-		const char *__old = (s);				\
-		size_t __len = strnlen(__old, (n));			\
-		char *__new = alloca(__len + 1);			\
-		__new[__len] = '\0';					\
-		memcpy(__new, __old, __len);				\
-	 })
-#endif
-
 #if !HAVE_DECL_BASENAME
 #include <string.h>
 static inline const char *basename(const char *s)

diff --git a/shared/util.c b/shared/util.c
@@ -387,9 +387,14 @@ static inline int is_dir(const char *path)
 
 int mkdir_p(const char *path, int len, mode_t mode)
 {
-	char *start, *end;
+	_cleanup_free_ char *start;
+	char *end;
 
-	start = strndupa(path, len);
+	start = memdup(path, len + 1);
+	if (!start)
+		return -ENOMEM;
+
+	start[len] = '\0';
 	end = start + len;
 
 	/*