Date: Thu, 7 May 2020 00:46:11 +0300 From: Konstantin Belousov <kib@freebsd.org> To: Damjan Jovanovic <damjan.jov@gmail.com> Cc: Hackers freeBSD <freebsd-hackers@freebsd.org> Subject: Re: Allow procstat to view current working directory? [xfce4-terminal, linprocfs, ...] Message-ID: <20200506214611.GD3866@kib.kiev.ua> In-Reply-To: <CAJm2B-=ja7u30xhVbT_8EX96ieBm%2BkqfTaT=1qfBD2B%2BZ9cCWg@mail.gmail.com> References: <CAJm2B-=ja7u30xhVbT_8EX96ieBm%2BkqfTaT=1qfBD2B%2BZ9cCWg@mail.gmail.com>
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On Wed, May 06, 2020 at 08:32:08PM +0200, Damjan Jovanovic wrote: > 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. Can you explain why CANDEBUG vs CANSEE matters for your case ? Or better, why xfce4-terminal cannot debug shells it spawns ? Is it suid ? My initial reaction was that linprocfs should be patched to match FreeBSD native behaviour instead. > > 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 > _______________________________________________ > freebsd-hackers@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-hackers > To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org"
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