strncpy() is deprecated for use on NUL-terminated destination strings [1] and as such we should prefer more robust and less ambiguous string interfaces. We expect db_root and db_root_stage to be NUL-terminated based on its immediate use with pr_debug which expects a C-string argument (%s). Moreover, it seems NUL-padding is not required. Considering the above, a suitable replacement is `strscpy` [2] due to the fact that it guarantees NUL-termination on the destination buffer without unnecessarily NUL-padding. Additionally, we should also change snprintf() to scnprintf(). `read_bytes` may be improperly assigned as snprintf() does NOT return the number of bytes written into the destination buffer, rather it returns the number of bytes that COULD have been written to that buffer if it had ample space. Conversely, scnprintf() returns the actual number of bytes written into the destination buffer (except the NUL-byte). This essentially means the ``if (!read_bytes)`` was probably never a possible branch. After these changes, this code is more self-describing since it uses string APIs that more accurately match the desired behavior. Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1] Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2] Link: https://github.com/KSPP/linux/issues/90 Cc: linux-hardening@xxxxxxxxxxxxxxx Signed-off-by: Justin Stitt <justinstitt@xxxxxxxxxx> --- Note: build-tested only. Found with: $ rg "strncpy\(" --- drivers/target/target_core_configfs.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/target/target_core_configfs.c b/drivers/target/target_core_configfs.c index c1fbcdd16182..d78647e4f6c5 100644 --- a/drivers/target/target_core_configfs.c +++ b/drivers/target/target_core_configfs.c @@ -123,7 +123,7 @@ static ssize_t target_core_item_dbroot_store(struct config_item *item, goto unlock; } - read_bytes = snprintf(db_root_stage, DB_ROOT_LEN, "%s", page); + read_bytes = scnprintf(db_root_stage, DB_ROOT_LEN, "%s", page); if (!read_bytes) goto unlock; @@ -143,7 +143,7 @@ static ssize_t target_core_item_dbroot_store(struct config_item *item, } filp_close(fp, NULL); - strncpy(db_root, db_root_stage, read_bytes); + strscpy(db_root, db_root_stage, sizeof(db_root)); pr_debug("Target_Core_ConfigFS: db_root set to %s\n", db_root); r = read_bytes; @@ -3651,7 +3651,7 @@ static void target_init_dbroot(void) { struct file *fp; - snprintf(db_root_stage, DB_ROOT_LEN, DB_ROOT_PREFERRED); + scnprintf(db_root_stage, DB_ROOT_LEN, DB_ROOT_PREFERRED); fp = filp_open(db_root_stage, O_RDONLY, 0); if (IS_ERR(fp)) { pr_err("db_root: cannot open: %s\n", db_root_stage); @@ -3664,7 +3664,7 @@ static void target_init_dbroot(void) } filp_close(fp, NULL); - strncpy(db_root, db_root_stage, DB_ROOT_LEN); + strscpy(db_root, db_root_stage, sizeof(db_root)); pr_debug("Target_Core_ConfigFS: db_root set to %s\n", db_root); } --- base-commit: bf3a69c6861ff4dc7892d895c87074af7bc1c400 change-id: 20240315-strncpy-drivers-target-target_core_configfs-c-fbe862bf950a Best regards, -- Justin Stitt <justinstitt@xxxxxxxxxx>
