| Message ID | 20230918-strncpy-drivers-block-null_blk-main-c-v2-1-cd9b109edfdf@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] null_blk: refactor deprecated strncpy | expand |
On 9/18/23 1:25 AM, Justin Stitt wrote:
> `strncpy` is deprecated for use on NUL-terminated destination strings [1].
Commit title again...
diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c index 864013019d6b..d83e65525e18 100644 --- a/drivers/block/null_blk/main.c +++ b/drivers/block/null_blk/main.c @@ -1938,7 +1938,7 @@ static int null_gendisk_register(struct nullb *nullb) else disk->fops = &null_bio_ops; disk->private_data = nullb; - strncpy(disk->disk_name, nullb->disk_name, DISK_NAME_LEN); + strscpy_pad(disk->disk_name, nullb->disk_name, DISK_NAME_LEN); if (nullb->dev->zoned) { int ret = null_register_zoned_dev(nullb);
`strncpy` is deprecated for use on NUL-terminated destination strings [1]. We should favor a more robust and less ambiguous interface. We expect that both `nullb->disk_name` and `disk->disk_name` be NUL-terminated: | snprintf(nullb->disk_name, sizeof(nullb->disk_name), | "%s", config_item_name(&dev->group.cg_item)); ... | pr_info("disk %s created\n", nullb->disk_name); It seems like NUL-padding may be required due to __assign_disk_name() utilizing a memcpy as opposed to a `str*cpy` api. | static inline void __assign_disk_name(char *name, struct gendisk *disk) | { | if (disk) | memcpy(name, disk->disk_name, DISK_NAME_LEN); | else | memset(name, 0, DISK_NAME_LEN); | } Then we go and print it with `__print_disk_name` which wraps `nullb_trace_disk_name()`. | #define __print_disk_name(name) nullb_trace_disk_name(p, name) This function obviously expects a NUL-terminated string. | const char *nullb_trace_disk_name(struct trace_seq *p, char *name) | { | const char *ret = trace_seq_buffer_ptr(p); | | if (name && *name) | trace_seq_printf(p, "disk=%s, ", name); | trace_seq_putc(p, 0); | | return ret; | } From the above, we need both 1) a NUL-terminated string and 2) a NUL-padded string. So, let's use strscpy_pad() as per Kees' suggestion from v1. Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1] Link: https://github.com/KSPP/linux/issues/90 Cc: linux-hardening@vger.kernel.org Cc: Kees Cook <keescook@chromium.org> Cc: Nick Desaulniers <ndesaulniers@google.com> Cc: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Justin Stitt <justinstitt@google.com> --- Changes in v2: - use strscpy_pad (thanks Kees) - Link to v1: https://lore.kernel.org/r/20230911-strncpy-drivers-block-null_blk-main-c-v1-1-3b3887e7fde4@google.com --- Note: build-tested --- drivers/block/null_blk/main.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- base-commit: 2dde18cd1d8fac735875f2e4987f11817cc0bc2c change-id: 20230911-strncpy-drivers-block-null_blk-main-c-7349153e1c6a Best regards, -- Justin Stitt <justinstitt@google.com>