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b=H4sIAPoxCWUC/5XNsQ6CMBSF4Vchnb2Gtijg5HsYY6C9QENpSYuNh PDuFibddDxn+P6FeHQKPbkkC3EYlFfWxMEPCRFdZVoEJeMmLGU8LSkFPzkjxhmkUwGdh1pb0YN 5av2odQ9DpQwIyHlW0hNHKs4VidbosFGvvXO7x90pP1k379lAt/ffQqBAgde8KHLMG4nZtbW21 XgUdiBbIrBPtviVZZEVsqxpWqJsZPPFruv6BiS8jjkyAQAA X-Developer-Key: i=justinstitt@google.com; a=ed25519; pk=tC3hNkJQTpNX/gLKxTNQKDmiQl6QjBNCGKJINqAdJsE= X-Developer-Signature: v=1; a=ed25519-sha256; t=1695101435; l=2972; i=justinstitt@google.com; s=20230717; h=from:subject:message-id; bh=RXCzkkhOQ+E9UQbcpoxWnHInR3mEf5rOQmZil2qhk+M=; b=FImjMy9YVwdq2HB1Atjs+s0JDQE+Fxn7+UN+L9PGSCOdB7Zi1ONJXuCKBxeO2KFrlKI9jCLp+ fdreS7InpzLCkCrpsn9S2Gxrmta6YbpzhETuSxVCpokVKbDdQow7atn X-Mailer: b4 0.12.3 Message-ID: <20230919-strncpy-drivers-block-null_blk-main-c-v3-1-10cf0a87a2c3@google.com> Subject: [PATCH v3] null_blk: replace strncpy with strscpy From: Justin Stitt To: Jens Axboe Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org, Kees Cook , Nick Desaulniers , Nathan Chancellor , Justin Stitt X-Spam-Status: No, score=-8.4 required=5.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lipwig.vger.email Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (lipwig.vger.email [0.0.0.0]); Mon, 18 Sep 2023 22:30:58 -0700 (PDT) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1777462987846421972 X-GMAIL-MSGID: 1777462987846421972 `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 Cc: Nick Desaulniers Cc: Nathan Chancellor Signed-off-by: Justin Stitt Reviewed-by: Kees Cook --- Changes in v3: - reword subject line (thanks Jens) - rebase onto 3669558bdf354cd352be955ef2764cde6a9bf5ec - Link to v2: https://lore.kernel.org/r/20230918-strncpy-drivers-block-null_blk-main-c-v2-1-cd9b109edfdf@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: 3669558bdf354cd352be955ef2764cde6a9bf5ec change-id: 20230911-strncpy-drivers-block-null_blk-main-c-7349153e1c6a Best regards, -- Justin Stitt diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c index 968090935eb2..6cd0614d8786 100644 --- a/drivers/block/null_blk/main.c +++ b/drivers/block/null_blk/main.c @@ -1946,7 +1946,7 @@ 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);