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Wed, 26 Aug 2026 14:17:07 +0000 (GMT) Received: from [0.0.0.0] (unknown [9.111.55.210]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTP; Wed, 26 Aug 2026 14:17:07 +0000 (GMT) Message-ID: <485c5bb3-ca8a-4591-827c-09d23f4280a2@linux.ibm.com> Date: Wed, 26 Aug 2026 16:17:07 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] s390: Warn if kernel command line contains non-printable EBCDIC characters To: Heiko Carstens Cc: Vasily Gorbik , Alexander Gordeev , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260825150840.537653-1-iii@linux.ibm.com> <20260826092916.21444Ab3-hca@linux.ibm.com> Content-Language: en-US From: Ilya Leoshkevich In-Reply-To: <20260826092916.21444Ab3-hca@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Info: AW1haW4tMjYwODI2MDExNiBTYWx0ZWRfX98hEewjzWKAA 1Ngr2T/sqRgKewhWz3eaRcDkwt0oTab2fSnxYYiAOvTIccOESYiH6UB1ZN7LGTdXecefa4vOCI6 Ie1OjZ16prRo30h/t8EGVk/juqR2oBQ= X-Proofpoint-GUID: PituprqXM9O2sbPkbuU6m5FcJLYbinxb X-Proofpoint-ORIG-GUID: PituprqXM9O2sbPkbuU6m5FcJLYbinxb X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODI2MDExNiBTYWx0ZWRfX+BbX7J7+jmh3 ZSZ3TTEzYLhPIHFTrrj+44gDfDmvFCRZO4+omq1CvKKz9JRZYKiOzs6bgTUscB5iy793Y7hEzCD s0rOB2MltY94MpmiW5P1FIFimZBUORDgD/Se7Q63TKIb2eEkhXbwXjlCuZpY7RLK8oQiZ+tcPn/ 1hCMGPBHLiaE6K/ykjetKOqII4tD3t97cYGC+Gnj5eQwkr12AWjrRzaERO2/iL+LMTetuZ4nxA5 C020a7rbokgNkJGF3QqJUaVeg+cDJCyez84v0V6bRbcL9ZYS/2qr73lxhsj4v0a67aCvhiHAJkd A/QKQYXP/J/G+9yRrLwJuFoTejhOXaqkKr5UUFwBDAvG4rX4P3zrbnUCGGRCitRZrCoBOYrHf5V jnQzztRArbu0H3qYRB7FdCjWwiQV+GILdOV/vMW7kJtBVkyi9vQf6gLuuYr5mOJpN5onuA4rkr4 k/EDzxHkoRkddlhsARQ== X-Authority-Analysis: v=2.4 cv=H7brBeYi c=1 sm=1 tr=0 ts=6a8ef568 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=VnNF1IyMAAAA:8 a=A3Q8tPC8mmVFCRH0wo0A:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-26_04,2026-08-26_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 malwarescore=0 lowpriorityscore=0 impostorscore=0 spamscore=0 bulkscore=0 adultscore=0 priorityscore=1501 clxscore=1015 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608260116 On 8/26/26 11:29, Heiko Carstens wrote: > On Tue, Aug 25, 2026 at 05:08:08PM +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. >> >> 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; > > Hm, I guess the comment refers to a different implementation than the > kernel internal one? Since isprint() (see include/linux/ctype.h) is > true for exactly the range you open-coded, as far as I can tell. Unfortunately isprint() matches some extra ASCII upper-half characters, e.g.: const unsigned char _ctype[] = { [...] _P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P,_P, /* 176-191 */ > Furthermore kernel command line parsing also allows for all sorts of > spaces, tabs, and line feeds (see e.g. next_arg()). So I guess the > above should be changed (and shortened :) ) to something like: I completely forgot about newlines, thanks! > static inline int has_nonprintable_char(const char *str) > { > for (int i = 0; str[i]; i++) { > if (isprint(str[i]) || isspace(str[i])) > return 1; > } > return 0; > }