On Mon, 2009-02-23 at 16:58 +0000, Sachin S. Prabhu wrote:
> Trond Myklebust wrote:
> > On Mon, 2009-02-23 at 16:22 +0000, Sachin S. Prabhu wrote:
> >> There is an inconsistency seen in the behaviour of nfs compared to other local
> >> filesystems on linux when changing owner or group of a directory. If the
> >> directory has SUID/SGID flags set, on changing owner or group on the directory,
> >> the flags are stripped off on nfs. These flags are maintained on other
> >> filesystems such as ext3.
> >>
> >> To reproduce on a nfs share or local filesystem, run the following commands
> >> mkdir test; chmod +s+g test; chown user1 test; ls -ld test
> >>
> >> On the nfs share, the flags are stripped and the output seen is
> >> drwxr-xr-x 2 user1 root 4096 Feb 23 2009 test
> >>
> >> On other local filesystems(ex: ext3), the flags are not stripped and the output
> >> seen is
> >> drwsr-sr-x 2 user1 root 4096 Feb 23 13:57 test
> >>
> >> chown_common() called from sys_chown() will only strip the flags if the inode is
> >> not a directory.
> >> static int chown_common(struct dentry * dentry, uid_t user, gid_t group)
> >> {
> >> ..
> >> if (!S_ISDIR(inode->i_mode))
> >> newattrs.ia_valid |=
> >> ATTR_KILL_SUID | ATTR_KILL_SGID | ATTR_KILL_PRIV;
> >> ..
> >> }
> >>
> >> See: http://www.opengroup.org/onlinepubs/7990989775/xsh/chown.html
> >>
> >> "If the path argument refers to a regular file, the set-user-ID (S_ISUID) and
> >> set-group-ID (S_ISGID) bits of the file mode are cleared upon successful return
> >> from chown(), unless the call is made by a process with appropriate privileges,
> >> in which case it is implementation-dependent whether these bits are altered. If
> >> chown() is successfully invoked on a file that is not a regular file, these
> >> bits may be cleared. These bits are defined in <sys/stat.h>."
> >>
> >> The behaviour as it stands does not appear to violate POSIX. However the
> >> actions performed are inconsistent when comparing ext3 and nfs.
> >
> > Does this patch retain the behaviour that we strip suid/sgid bits on
> > executable files?
> >
> > IOW: Is the following property retained
> >
> > root@heimdal:~# touch /tmp/gnurr; chmod a+x,+s+g /tmp/gnurr; chown
> > bin /tmp/gnurr
> > root@heimdal:~# ls -l /tmp/gnurr
> > -rwxr-xr-x 1 bin root 0 2009-02-23 08:49 /tmp/gnurr
> >
> Yes it does
>
> [root@vm22 mnt]# touch t2; chmod a+x,+s+g t2; chown bin t2
> [root@vm22 mnt]# ls -l t2
> -rwxr-xr-x 1 bin root 0 Feb 23 16:56 t2
>
> The behaviour changes only for directories.
> [root@vm22 mnt]# mkdir t3; chmod a+x,+s+g t3; chown bin t3
> [root@vm22 mnt]# ls -ld t3
> drwsr-sr-x 2 bin root 4096 Feb 23 16:57 t3
Fair enough. That makes sense...
Cheers
Trond
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