On Mon, Feb 23, 2009 at 04:22:03PM +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.
Makes sense, thanks!--applied for 2.6.30.--b.
>
> Sachin Prabhu
> Signed-off-by: Sachin Prabhu <sprabhu@xxxxxxxxxx>
> Acked-by: Jeff Layton <jlayton@xxxxxxxxxx>
> --- linux-2.6.29-rc2/fs/nfsd/vfs.c.orig 2009-02-23 06:45:20.000000000 -0500
> +++ linux-2.6.29-rc2/fs/nfsd/vfs.c 2009-02-23 11:10:10.000000000 -0500
> @@ -366,8 +366,9 @@
> }
>
> /* Revoke setuid/setgid on chown */
> - if (((iap->ia_valid & ATTR_UID) && iap->ia_uid != inode->i_uid) ||
> - ((iap->ia_valid & ATTR_GID) && iap->ia_gid != inode->i_gid)) {
> + if (!S_ISDIR(inode->i_mode) &&
> + (((iap->ia_valid & ATTR_UID) && iap->ia_uid != inode->i_uid) ||
> + ((iap->ia_valid & ATTR_GID) && iap->ia_gid != inode->i_gid))) {
> iap->ia_valid |= ATTR_KILL_PRIV;
> if (iap->ia_valid & ATTR_MODE) {
> /* we're setting mode too, just clear the s*id bits */
--
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