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[2a01:cb08:8949:7e00:2eae:79bb:f3d3:52f3]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-43ead3d5c8fsm4384790f8f.19.2026.04.15.03.45.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Apr 2026 03:45:01 -0700 (PDT) Date: Wed, 15 Apr 2026 12:44:59 +0200 From: Paul Chaignon To: Yihan Ding Cc: bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, shuah@kernel.org, linux-kernel@vger.kernel.org, alan.maguire@oracle.com, kernel@uniontech.com Subject: Re: [PATCH bpf v2 1/2] bpf: allow UTF-8 literals in bpf_bprintf_prepare() Message-ID: References: <20260415032126.1096299-1-dingyihan@uniontech.com> <20260415032126.1096299-2-dingyihan@uniontech.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260415032126.1096299-2-dingyihan@uniontech.com> On Wed, Apr 15, 2026 at 11:21:25AM +0800, Yihan Ding wrote: > bpf_bprintf_prepare() only needs ASCII parsing for conversion > specifiers. Plain text can safely carry bytes >= 0x80, so allow > UTF-8 literals outside '%' sequences while keeping ASCII control > bytes rejected and format specifiers ASCII-only. > > This keeps existing parsing rules for format directives unchanged, > while allowing helpers such as bpf_trace_printk() to emit UTF-8 > literal text. > > Fixes: 48cac3f4a96d ("bpf: Implement formatted output helpers with bstr_printf") > Suggested-by: Paul Chaignon I don't think this tag is appropriate here. If you want to give credit for changes made after reviews, you can do so in the Changelogs of the cover letter :) > Signed-off-by: Yihan Ding > --- > kernel/bpf/helpers.c | 16 +++++++++++++++- > 1 file changed, 15 insertions(+), 1 deletion(-) > > diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c > index 6eb6c82ed2ee..6319b39c92f9 100644 > --- a/kernel/bpf/helpers.c > +++ b/kernel/bpf/helpers.c > @@ -845,7 +845,13 @@ int bpf_bprintf_prepare(const char *fmt, u32 fmt_size, const u64 *raw_args, > data->buf = buffers->buf; > > for (i = 0; i < fmt_size; i++) { > - if ((!isprint(fmt[i]) && !isspace(fmt[i])) || !isascii(fmt[i])) { > + unsigned char c = fmt[i]; > + > + /* > + * Permit bytes >= 0x80 in plain text so UTF-8 literals can pass > + * through unchanged, while still rejecting ASCII control bytes. > + */ > + if (isascii(c) && !isprint(c) && !isspace(c)) { > err = -EINVAL; > goto out; > } > @@ -867,6 +873,14 @@ int bpf_bprintf_prepare(const char *fmt, u32 fmt_size, const u64 *raw_args, > * always access fmt[i + 1], in the worst case it will be a 0 > */ > i++; > + /* > + * The format parser below only understands ASCII conversion > + * specifiers and modifiers, so reject non-ASCII after '%'. > + */ > + if (!isascii((unsigned char)fmt[i])) { > + err = -EINVAL; > + goto out; > + } Acked-by: Paul Chaignon > > /* skip optional "[0 +-][num]" width formatting field */ > while (fmt[i] == '0' || fmt[i] == '+' || fmt[i] == '-' || > -- > 2.20.1