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Fri, 27 Sep 2024 11:18:10 -0400 (EDT) From: Tycho Andersen To: Alexander Viro , Christian Brauner , Jan Kara , Eric Biederman , Kees Cook Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Tycho Andersen , Tycho Andersen , =?utf-8?q?Zbigniew_J=C4=99drzejewski-Szmek?= , Aleksa Sarai Subject: [PATCH v2 1/2] exec: add a flag for "reasonable" execveat() comm Date: Fri, 27 Sep 2024 09:17:45 -0600 Message-Id: <20240927151746.391931-1-tycho@tycho.pizza> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-Stat-Signature: 17f1t459hd3wgp3pi49sxiwwc46j4gf1 X-Rspamd-Queue-Id: 35CC520005 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1727450294-635540 X-HE-Meta: U2FsdGVkX1/uSWTOvdueepaY0Ay4tO6mBql9PzMUbreF1Smblv8yboO1otd2MpJbDSZp5d66/5kKYDgIpoZ+V4E1nRXlStv34lqi2wAHWodToABrR5rw25Rkq18StXdqz3LYU//YXnNseru0tDkdQNYU/5kIFho7ef0Or2tuxnP3lSvVxZVLcQkUEQDXHjHhDspQ+jeoRJiolWRH4LTgID6Q1cgs2m61ncUMaihRH4OtG9//kiO0MmE7j27whDAk02l6ROu1W82e/nFOa4ftCVTK7V6izZ7NCckmQQjumQwKhm9uvUPQfz+oJs57xaMQumTefIgiNrECNFLwhbipqhIFm4Xu4eKHjsgeNwd6fHKwARoPP1aGauvKfHcyQI6gqJxsHzXd0obRaNpK4BqpWcvrjdZ/wafPwISUTgsRnGLpqM7dnijlYm5RUAa3b4a9twOdByhGpf5JtS2qURVuD2W3GXt9P+Hv7CP5RFyWpYcrUQvpyS3PM5Bd+MPaEezl++W5w/OFS0Oiuozk/A9s9r6JpuqpV6OTnJbzS5PV9eGIcTyAK8zM+l+BqYoFBTKKdqhT4ZwLeYDukF2cJ/8MJNcpXJgNtdlUje6q0y4MO/fMMXn7eRcd9BWOWCsFX5OYn23ESrKEurMSaLrd1jjLt72Fbwbsx+kfKMo5vZGXgBDTLrLEFsjZZbGmCAG/jN+PSdWFtYSzZ/8RK8FuUb9X9OsA6+7Q1c4A9aRr7SmsB46RmkeP8qZTaeZ65rkKeVP7W/S9iFhJnT/iBte7+o2GJQ09ODk3EXJHp0F5jHK7OSk3MTLxUshB9D+5COQb2xOEqtIu8lM6eRVtBqOTPXxPe13ARUOPQDORdWvboHLZugNC8XuGQij1Sb72Qw8WYYOB1ni04Dmt9CwCpZSIp440aLZUCgTiAb8Siw1a1gT+JgT7z5vX24bZ99OjAD+cs1EQWc6AYIEqlMblhSBhXSE 8Wdt5XKq FY43XNrNnwOinSAnbpsNTUupPoP7RAYO66ruiVoHBsiNqY35amgypxQ9UpaN77fI44J4AdLBsTGehH6znhrxwlOIeblk9PYXQKOsn90e7gnVxYHphsBKx7vu9kaSX1SX7V31rX5dQBkGvhdcyrXCk122P5P0e9buEYMfx/bmTRx/6d6K8h03lhs/VDY4zX62tfn6EPfai1sPVhhEcYKsH2Kj9GD25TbWsb4SBIKqWdj6YlG7SOBaF/P5OpfK0ZuxYSHnGwzskG9URQuwpIsOFzLE2LAu+z79/LysFzF7FVHxZtGl8AbbDZpCQvC2sJeRfkv+qMuYP5kDWQeYvpKOjqrXbe67j/4pgPgQLYjS0zEjptSEAhvQe4QA+uswxIBkvR+/w8GOaavmVBYo= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Tycho Andersen Zbigniew mentioned at Linux Plumber's that systemd is interested in switching to execveat() for service execution, but can't, because the contents of /proc/pid/comm are the file descriptor which was used, instead of the path to the binary. This makes the output of tools like top and ps useless, especially in a world where most fds are opened CLOEXEC so the number is truly meaningless. Change exec path to fix up /proc/pid/comm in the case where we have allocated one of these synthetic paths in bprm_init(). This way the actual exec machinery is unchanged, but cosmetically the comm looks reasonable to admins investigating things. Signed-off-by: Tycho Andersen Suggested-by: Zbigniew Jędrzejewski-Szmek CC: Aleksa Sarai Link: https://github.com/uapi-group/kernel-features#set-comm-field-before-exec --- v2: * drop the flag, everyone :) * change the rendered value to f_path.dentry->d_name.name instead of argv[0], Eric --- fs/exec.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) base-commit: baeb9a7d8b60b021d907127509c44507539c15e5 diff --git a/fs/exec.c b/fs/exec.c index dad402d55681..9520359a8dcc 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1416,7 +1416,18 @@ int begin_new_exec(struct linux_binprm * bprm) set_dumpable(current->mm, SUID_DUMP_USER); perf_event_exec(); - __set_task_comm(me, kbasename(bprm->filename), true); + + /* + * If fdpath was set, execveat() made up a path that will + * probably not be useful to admins running ps or similar. + * Let's fix it up to be something reasonable. + */ + if (bprm->fdpath) { + BUILD_BUG_ON(TASK_COMM_LEN > DNAME_INLINE_LEN); + __set_task_comm(me, bprm->file->f_path.dentry->d_name.name, true); + } else { + __set_task_comm(me, kbasename(bprm->filename), true); + } /* An exec changes our domain. We are no longer part of the thread group */