Date: Wed, 6 May 2020 20:32:08 +0200 From: Damjan Jovanovic <damjan.jov@gmail.com> To: Hackers freeBSD <freebsd-hackers@freebsd.org> Subject: Allow procstat to view current working directory? [xfce4-terminal, linprocfs, ...] Message-ID: <CAJm2B-=ja7u30xhVbT_8EX96ieBm%2BkqfTaT=1qfBD2B%2BZ9cCWg@mail.gmail.com>
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Hi Currently "procstat fd [pid]" cannot view anything, even for other processes owned by the user making the call, not even their current working directory (CWD), unless it has PGET_CANDEBUG permission. linprocfs however allows reading the CWD for any process because it doesn't perform that check (sys/compat/linprocfs/linprocfs.c, function linprocfs_doproccwd()). Applications use this, eg. xfce4-terminal relies on /compat/linux/proc/<pid>/cwd to find the shell's CWD, so that when you open a new tab, it starts in the same CWD as the tab you opened it from ( https://github.com/xfce-mirror/xfce4-terminal/blob/master/terminal/terminal-screen.c#L2343). I would like to patch xfce4-terminal to use libprocstat for that instead of needing linprocfs to be mounted, but since procstat is more restrictive, it will break it. Can we please downgrade PGET_CANDEBUG to at least PGET_CANSEE, so you can view the CWD for processes you own? Maybe other open files still need to be hidden, but the CWD doesn't seem like a major security concern. Linux's own /proc filesystem never hides the CWD (lrwxrwxrwx), and only hides file descriptors for processes you don't own. A patch along the following lines could be a start: diff --git a/sys/kern/kern_descrip.c b/sys/kern/kern_descrip.c index 423968b2e1cc..f487232d2cff 100644 --- a/sys/kern/kern_descrip.c +++ b/sys/kern/kern_descrip.c @@ -3692,7 +3692,7 @@ sysctl_kern_proc_filedesc(SYSCTL_HANDLER_ARGS) sbuf_new_for_sysctl(&sb, NULL, FILEDESC_SBUF_SIZE, req); sbuf_clear_flags(&sb, SBUF_INCLUDENUL); - error = pget((pid_t)name[0], PGET_CANDEBUG | PGET_NOTWEXIT, &p); + error = pget((pid_t)name[0], PGET_CANSEE | PGET_NOTWEXIT, &p); if (error != 0) { sbuf_delete(&sb); return (error); @@ -3768,7 +3768,7 @@ sysctl_kern_proc_ofiledesc(SYSCTL_HANDLER_ARGS) struct proc *p; name = (int *)arg1; - error = pget((pid_t)name[0], PGET_CANDEBUG | PGET_NOTWEXIT, &p); + error = pget((pid_t)name[0], PGET_CANSEE | PGET_NOTWEXIT, &p); if (error != 0) return (error); fdp = fdhold(p); Thank you Damjan
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