| Message ID | 20240927151746.391931-1-tycho@tycho.pizza (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v2,1/2] exec: add a flag for "reasonable" execveat() comm | expand |
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. It should be 99% application invisible as all an application can see is argv0. So it is only ps and friends where the comm value is visible. Eric
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 */