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Mon, 17 Feb 2025 16:16:39 GMT Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 5A60520043; Mon, 17 Feb 2025 16:16:39 +0000 (GMT) Received: from smtpav01.fra02v.mail.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D188820040; Mon, 17 Feb 2025 16:16:38 +0000 (GMT) Received: from osiris (unknown [9.171.53.224]) by smtpav01.fra02v.mail.ibm.com (Postfix) with ESMTPS; Mon, 17 Feb 2025 16:16:38 +0000 (GMT) Date: Mon, 17 Feb 2025 17:16:37 +0100 From: Heiko Carstens To: Heiko Carstens Cc: Haoxiang Li , gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, schwidefsky@de.ibm.com, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] s390/sclp: Add check for get_zeroed_page() Message-ID: <20250217161637.21424Ce0-hca@linux.ibm.com> References: <20250217153146.2372134-1-haoxiang_li2024@163.com> <20250217160117.21424B3d-hca@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-s390@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: <20250217160117.21424B3d-hca@linux.ibm.com> X-TM-AS-GCONF: 00 X-Proofpoint-GUID: usbjZRp83svHyQjJRBvcKteDeGxxMZg6 X-Proofpoint-ORIG-GUID: V3XVaIvsNwwoLAuwNN3QD1XP3BNLikx6 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1057,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-02-17_06,2025-02-13_01,2024-11-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 bulkscore=0 malwarescore=0 priorityscore=1501 suspectscore=0 impostorscore=0 lowpriorityscore=0 spamscore=0 clxscore=1015 mlxscore=0 mlxlogscore=645 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2501170000 definitions=main-2502170132 On Mon, Feb 17, 2025 at 05:01:17PM +0100, Heiko Carstens wrote: > On Mon, Feb 17, 2025 at 11:31:46PM +0800, Haoxiang Li wrote: > > diff --git a/drivers/s390/char/sclp_con.c b/drivers/s390/char/sclp_con.c > > index e5d947c763ea..7447076b1ec1 100644 > > --- a/drivers/s390/char/sclp_con.c > > +++ b/drivers/s390/char/sclp_con.c > > @@ -282,6 +282,8 @@ sclp_console_init(void) > > /* Allocate pages for output buffering */ > > for (i = 0; i < sclp_console_pages; i++) { > > page = (void *) get_zeroed_page(GFP_KERNEL | GFP_DMA); > > + if (!page) > > + return -ENOMEM; > > list_add_tail(page, &sclp_con_pages); > > We can add this check, however if this early allocation would fail a > null pointer dereference would be the last problem we would have to > think about. > > Anyway: > Acked-by: Heiko Carstens Wait, I take that back. Now I think I remember why I didn't add error handling back then: the above exit would also indicate a potential memory leak, since this is a loop allocating several pages; so all already allocated pages must be freed, which would ask for even more completely pointless error handling. This is very early code where any allocation failure would lead to a crash in any case. So either do the full exercise or we leave the code as it is.