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shared: use memdup over stdndupa

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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 <emil.l.velikov@gmail.com>
Link: https://github.com/kmod-project/kmod/pull/92
Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>
This commit is contained in:
Emil Velikov 2024-08-22 17:04:21 +01:00 committed by Lucas De Marchi
parent 7a1de13a54
commit b27aa3fb5a
3 changed files with 8 additions and 16 deletions
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3
configure.ac
View File

@ -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(

12
shared/missing.h
View File

@ -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)

9
shared/util.c
View File

@ -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;
/*