kern/157234: //proc/curproc/file returns "unknown" with a binary called via a nullfs mountpoint

[Patrick Lamaiziere]

The following reply was made to PR kern/157234; it has been noted by GNATS.

From: Patrick Lamaiziere <patfbsd at davenulle.org>
To: bug-followup at FreeBSD.org <bug-followup at FreeBSD.org>
Cc:  
Subject: Re: kern/157234: //proc/curproc/file returns "unknown" with a
 binary called via a nullfs mountpoint
Date: Sat, 21 May 2011 15:34:18 +0200

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 Le Sat, 21 May 2011 11:18:00 GMT,
 Patrick Lamaiziere <patfbsd at davenulle.org> a écrit :
 
 > /proc/curproc/file returns "unknown" with a binary called via a
 > nullfs mountpoint, but not if called directly.
 
 Well, i've looked a bit the procfs code and this behavior seems
 more or less intented by the function vn_fullpath(9).
 
 procstat(1) is affected too : procstat: sysctl: kern.proc.pathname:
 2265: No such file or directory
 
 So it looks to be a limitation instead of a bug.
 
 I would like to suggest to reclassify this PR into the doc section and
 the attached patch to document the nulls manual page (as usual feel
 free to change the text as english is not my natural language).
 
 Thanks, regards
 
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 --- nullfs.5.org	2011-05-21 14:37:23.000000000 +0200
 +++ nullfs.5	2011-05-21 15:00:38.000000000 +0200
 @@ -56,6 +56,16 @@
  file system:
  .Pp
  .Dl "mount_nullfs /usr/ports /home/devel/ports"
 +.Sh CAVEAT
 +The
 +.Nm
 +file system prevents to convert a vnode reference to a full pathname, given a
 +process context. This will prevent an application to retrieve its path
 +to process binary. For example, applications using the
 +.Xr procfs 5
 +file system /proc/curproc/file or the 
 +.Xr sysctl 8
 +kern.proc.pathname
  .Sh SEE ALSO
  .Xr fstab 5 ,
  .Xr mount_nullfs 8
 
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