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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-482e27a9f0esm2851620f8f.10.2026.08.26.06.51.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 26 Aug 2026 06:51:31 -0700 (PDT) Date: Wed, 26 Aug 2026 14:51:29 +0100 From: David Laight To: Ilya Leoshkevich Cc: Heiko Carstens , Vasily Gorbik , Alexander Gordeev , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] s390: Warn if kernel command line contains non-printable EBCDIC characters Message-ID: <20260826145129.204b6517@pumpkin> In-Reply-To: <20260825150840.537653-1-iii@linux.ibm.com> References: <20260825150840.537653-1-iii@linux.ibm.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) 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-Transfer-Encoding: 7bit On Tue, 25 Aug 2026 17:08:08 +0200 Ilya Leoshkevich wrote: > Users may accidentally add multi-byte UTF-8 characters to zipl.conf > parmline, for example, by copying snippets containing non-breaking > spaces (\xC2\xA0) from web pages. > > The kernel will then interpret the entire command line as EBCDIC, > making it unusable. Distinguish this situation from the legitimate > EBCDIC conversion by looking for non-printable characters and issue > a warning. Would it be better to check for the entire line being printable ebcdic? All of EBCDIC a-zA-Z0-9 have the 0x80 bit set and most of 0x20..0x7f are invalid or control characters (or punctuation). David > > Signed-off-by: Ilya Leoshkevich > --- > arch/s390/boot/ipl_parm.c | 19 ++++++++++++++++++- > 1 file changed, 18 insertions(+), 1 deletion(-) > > diff --git a/arch/s390/boot/ipl_parm.c b/arch/s390/boot/ipl_parm.c > index 6bc950b92be76..71c0c26d56bba 100644 > --- a/arch/s390/boot/ipl_parm.c > +++ b/arch/s390/boot/ipl_parm.c > @@ -173,12 +173,29 @@ static inline int has_ebcdic_char(const char *str) > return 0; > } > > +static inline int has_nonprintable_char(const char *str) > +{ > + int i; > + > + for (i = 0; str[i]; i++) { > + unsigned char c = (unsigned char)str[i]; > + > + /* isprint() is Latin-1, and we need ASCII here */ > + if (c < 0x20 || c > 0x7e) > + return 1; > + } > + return 0; > +} > + > void setup_boot_command_line(void) > { > parmarea.command_line[COMMAND_LINE_SIZE - 1] = 0; > /* convert arch command line to ascii if necessary */ > - if (has_ebcdic_char(parmarea.command_line)) > + if (has_ebcdic_char(parmarea.command_line)) { > EBCASC(parmarea.command_line, COMMAND_LINE_SIZE); > + if (has_nonprintable_char(parmarea.command_line)) > + boot_warn("Kernel command line was treated as EBCDIC, but contains non-printable characters\n"); > + } > /* copy arch command line */ > strscpy(early_command_line, strim(parmarea.command_line)); >