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Tue, 11 Jan 2022 20:49:01 +0000 (GMT) Received: from tuxmaker.linux.ibm.com (unknown [9.152.85.9]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTPS; Tue, 11 Jan 2022 20:49:01 +0000 (GMT) From: Sven Schnelle To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Andrew Morton , Masami Hiramatsu , Tom Zanussi , stable@vger.kernel.org, Pingfan Liu Subject: Re: [PATCH 2/2] tracing: Add test for user space strings when filtering on string pointers References: <20220107225655.647376947@goodmis.org> <20220107225840.003487216@goodmis.org> Date: Tue, 11 Jan 2022 21:49:01 +0100 In-Reply-To: <20220107225840.003487216@goodmis.org> (Steven Rostedt's message of "Fri, 07 Jan 2022 17:56:57 -0500") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.0.50 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: HrRNlRYq5xzOVqxasedEk3L3llRklEWD X-Proofpoint-GUID: EAKNwtcVpZGUwgai_6J1lzq1tgRLNq7n X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.790,Hydra:6.0.425,FMLib:17.11.62.513 definitions=2022-01-11_04,2022-01-11_01,2021-12-02_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 adultscore=0 mlxlogscore=912 spamscore=0 lowpriorityscore=0 bulkscore=0 phishscore=0 priorityscore=1501 suspectscore=0 impostorscore=0 clxscore=1011 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2110150000 definitions=main-2201110107 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Steve, Steven Rostedt writes: > From: Steven Rostedt > > Pingfan reported that the following causes a fault: > > echo "filename ~ \"cpu\"" > events/syscalls/sys_enter_openat/filter > echo 1 > events/syscalls/sys_enter_at/enable > [..] > +static __always_inline char *test_string(char *str) > +{ > + struct ustring_buffer *ubuf; > + char __user *ustr; > + char *kstr; > + > + if (!ustring_per_cpu) > + return NULL; > + > + ubuf = this_cpu_ptr(ustring_per_cpu); > + kstr = ubuf->buffer; > + > + if (likely((unsigned long)str >= TASK_SIZE)) { I think that would not work on architectures where addresses for kernel and user space could overlap, i.e. with different address spaces? > + /* For safety, do not trust the string pointer */ > + if (!strncpy_from_kernel_nofault(kstr, str, USTRING_BUF_SIZE)) > + return NULL; > + } else { > + /* user space address? */ > + ustr = str; > + if (!strncpy_from_user_nofault(kstr, ustr, USTRING_BUF_SIZE)) > + return NULL; > + } > + return kstr; > +}