um: Remove strlcpy declaration

strlcpy() reads the entire source buffer first.
This read may exceed the destination size limit.
This is both inefficient and can lead to linear read
overflows if a source string is not NUL-terminated [1].
In an effort to remove strlcpy() completely [2], replace
strlcpy() here with strscpy().
No return values were used, so direct replacement is safe.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] https://github.com/KSPP/linux/issues/89

Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20230703160641.1790935-1-azeemshaikh38@gmail.com
Signed-off-by: Kees Cook <keescook@chromium.org>

diff --git a/arch/um/include/shared/user.h b/arch/um/include/shared/user.h
index 0347a19..981e11d 100644 (file)
--- a/arch/um/include/shared/user.h
+++ b/arch/um/include/shared/user.h
@@ -50,7 +50,6 @@ static inline int printk(const char *fmt, ...)
 #endif
 
 extern int in_aton(char *str);
-extern size_t strlcpy(char *, const char *, size_t);
 extern size_t strlcat(char *, const char *, size_t);
 extern size_t strscpy(char *, const char *, size_t);
 

diff --git a/arch/um/os-Linux/umid.c b/arch/um/os-Linux/umid.c
index 7a1abb8..288c422 100644 (file)
--- a/arch/um/os-Linux/umid.c
+++ b/arch/um/os-Linux/umid.c
@@ -40,7 +40,7 @@ static int __init make_uml_dir(void)
                                __func__);
                        goto err;
                }
-               strlcpy(dir, home, sizeof(dir));
+               strscpy(dir, home, sizeof(dir));
                uml_dir++;
        }
        strlcat(dir, uml_dir, sizeof(dir));
@@ -243,7 +243,7 @@ int __init set_umid(char *name)
        if (strlen(name) > UMID_LEN - 1)
                return -E2BIG;
 
-       strlcpy(umid, name, sizeof(umid));
+       strscpy(umid, name, sizeof(umid));
 
        return 0;
 }
@@ -262,7 +262,7 @@ static int __init make_umid(void)
        make_uml_dir();
 
        if (*umid == '\0') {
-               strlcpy(tmp, uml_dir, sizeof(tmp));
+               strscpy(tmp, uml_dir, sizeof(tmp));
                strlcat(tmp, "XXXXXX", sizeof(tmp));
                fd = mkstemp(tmp);
                if (fd < 0) {