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Mon, 27 Apr 2026 02:38:44 -0700 (PDT) Received: from [192.168.1.167] ([185.168.96.228]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-50fc91de051sm122402911cf.2.2026.04.27.02.38.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 27 Apr 2026 02:38:44 -0700 (PDT) Message-ID: <76fb702caa9aa7cd18deaea4fd7e2cbf32a76f44.camel@redhat.com> Subject: Re: [PATCH] tools/rv: harden monitor name lookup bounds checks From: Gabriele Monaco To: unknownbbqrx Cc: rostedt@goodmis.org, linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org Date: Mon, 27 Apr 2026 11:38:42 +0200 In-Reply-To: <69972ccf-31ee-4906-9907-0ead76bd60b9@smtp-relay.sendinblue.com> References: <69972ccf-31ee-4906-9907-0ead76bd60b9@smtp-relay.sendinblue.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.58.3 (3.58.3-1.fc43) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Thu, 2026-04-23 at 17:44 +0300, unknownbbqrx wrote: >=20 > Bound monitor-name derived copies in __ikm_find_monitor_name() and > avoid unbounded writes from sprintf()/memcpy(). >=20 > Pass the output buffer size from the caller, validate extracted line > length from rv/available_monitors, and use snprintf() with truncation > checks when building container monitor names. >=20 > Signed-off-by: unknownbbqrx Hi, thanks for the fix, however __ikm_find_monitor_name() is already a bit sloppy (strstr can take any substring as a valid monitor) so I have a patch to refactor it, which I'm about to send. This will make your fix obsolete so I'm likely not going to take this patch. Thanks anyway, Gabriele > --- > =C2=A0tools/verification/rv/src/in_kernel.c | 34 +++++++++++++++++++++---= - > -- > =C2=A01 file changed, 27 insertions(+), 7 deletions(-) >=20 > diff --git a/tools/verification/rv/src/in_kernel.c > b/tools/verification/rv/src/in_kernel.c > index d32453824..f17eac9b6 100644 > --- a/tools/verification/rv/src/in_kernel.c > +++ b/tools/verification/rv/src/in_kernel.c > @@ -56,9 +56,12 @@ static int __ikm_read_enable(char *monitor_name) > =C2=A0 * The string out_name is populated with the full name, which can b= e > =C2=A0 * equal to monitor_name or container/monitor_name if nested > =C2=A0 */ > -static int __ikm_find_monitor_name(char *monitor_name, char > *out_name) > +static int __ikm_find_monitor_name(char *monitor_name, char > *out_name, > + =C2=A0 size_t out_name_size) > =C2=A0{ > - char *available_monitors, container[MAX_DA_NAME_LEN+1], > *cursor, *end; > + char *available_monitors, container[MAX_DA_NAME_LEN + 2], > *cursor, *end; > + size_t len; > + int n; > =C2=A0 int retval =3D 1; > =C2=A0 > =C2=A0 available_monitors =3D tracefs_instance_file_read(NULL, > "rv/available_monitors", NULL); > @@ -72,17 +75,34 @@ static int __ikm_find_monitor_name(char > *monitor_name, char *out_name) > =C2=A0 } > =C2=A0 > =C2=A0 for (; cursor > available_monitors; cursor--) > - if (*(cursor-1) =3D=3D '\n') > + if (*(cursor - 1) =3D=3D '\n') > =C2=A0 break; > + > =C2=A0 end =3D strstr(cursor, "\n"); > - memcpy(out_name, cursor, end-cursor); > - out_name[end-cursor] =3D '\0'; > + if (!end) { > + retval =3D -1; > + goto out_free; > + } > + > + len =3D end - cursor; > + if (len >=3D out_name_size) { > + retval =3D -1; > + goto out_free; > + } > + > + memcpy(out_name, cursor, len); > + out_name[len] =3D '\0'; > =C2=A0 > =C2=A0 cursor =3D strstr(out_name, ":"); > =C2=A0 if (cursor) > =C2=A0 *cursor =3D '/'; > =C2=A0 else { > - sprintf(container, "%s:", monitor_name); > + n =3D snprintf(container, sizeof(container), "%s:", > monitor_name); > + if (n < 0 || (size_t)n >=3D sizeof(container)) { > + retval =3D -1; > + goto out_free; > + } > + > =C2=A0 if (strstr(available_monitors, container)) > =C2=A0 config_is_container =3D 1; > =C2=A0 } > @@ -782,7 +802,7 @@ int ikm_run_monitor(char *monitor_name, int argc, > char **argv) > =C2=A0 else > =C2=A0 nested_name =3D monitor_name; > =C2=A0 > - retval =3D __ikm_find_monitor_name(monitor_name, full_name); > + retval =3D __ikm_find_monitor_name(monitor_name, full_name, > sizeof(full_name)); > =C2=A0 if (!retval) > =C2=A0 return 0; > =C2=A0 if (retval < 0) { >=20 > base-commit: 2e68039281932e6dc37718a1ea7cbb8e2cda42e6 > prerequisite-patch-id: b61dd51dee390277603975bf729a687113185c3a