On Fri, Sep 27, 2024 at 10:45:58AM -0500, Eric W. Biederman wrote:
Tycho Andersen tycho@tycho.pizza writes:
From: Tycho Andersen tandersen@netflix.com
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.
Perhaps change the subject to match the code.
Signed-off-by: Tycho Andersen tandersen@netflix.com Suggested-by: Zbigniew Jędrzejewski-Szmek zbyszek@in.waw.pl CC: Aleksa Sarai cyphar@cyphar.com 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(-)
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);We can just do this regardless of bprm->fdpath.
It will be a change of behavior on when executing symlinks and possibly mount points but I don't think we care. If we do then we can add make it conditional with "if (bprm->fdpath)"
At the very least using the above version unconditionally ought to flush out any bugs.
I'm not super comfortable doing this regardless of bprm->fdpath; that seems like too many cases getting changed. Can we just leave it as depending on bprm->fdpath?
Also, is d_name.name always going to be set? e.g. what about memfd, etc?