Re: [PATCH v5 09/12] seq_buf: Add seq_buf_init_append()

[Steven Rostedt <rostedt@goodmis.org>]

On Mon,  5 Oct 2026 08:56:59 -0700
Kees Cook <kees@kernel.org> wrote:

> From: Bill Wendling <morbo@google.com>
> 
> Several strlcat() call sites being converted to seq_buf need behavior
> seq_buf doesn't currently provide. The normal seq_buf_init() always
> empties the buffer (sets its "len" to 0) via seq_buf_clear(). Code
> migrating from strlcat(buf, ...), which appends to whatever buf already
> contains, can't use seq_buf_init() without discarding that existing
> content. Add seq_buf_init_append(), which preserves the existing
> contents and positions the seq_buf to append after it. A buffer with
> no NUL within its size starts out overflowed, as strlcat() treats it
> as already truncated. Add KUnit tests for behavior coverage.
> 
> Tests passed under qemu on ARCH=x86_64 with GCC 16.2.0 and CONFIG_KASAN=y,
> and on big-endian ARCH=s390 with GCC s390x-linux-gnu 16.2.0.
> 
> Assisted-by: LLM
> Signed-off-by: Bill Wendling <morbo@google.com>
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Co-developed-by: Kees Cook <kees@kernel.org>
> Signed-off-by: Kees Cook <kees@kernel.org>
> ---

Reviewed-by: Steven Rostedt <rostedt@goodmis.org>

-- Steve