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    SubjectRe: [PATCH v3] null_blk: replace strncpy with strscpy
    On Tue, Sep 19, 2023 at 05:30:35AM +0000, Justin Stitt wrote:
    > `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>

    Ping on this one too. Jens, can you pick this up?

    Thanks!

    -Kees

    --
    Kees Cook

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