On Sun, Apr 13, 2014 at 11:11:39PM +0800, Kinglong Mee wrote:
> As local filesystem, writing data to the file by non-owner will
> clears the SUID+SGID, owner will not.
Are you sure about this? (Do you have a test case that fails?)
I don't see an owner check in should_remove_suid.
And I think that an nfsd thread will always have CAP_FSETID set (see
cap_raise_nfsd_set and the definition of CAP_NFSD_SET), so that
should_remove_suid() will always return 0.
--b.
>
> Signed-off-by: Kinglong Mee <kinglongmee@xxxxxxxxx>
> ---
> fs/nfsd/vfs.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
> index 16f0673..19c0931 100644
> --- a/fs/nfsd/vfs.c
> +++ b/fs/nfsd/vfs.c
> @@ -943,7 +943,7 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh
> *fhp, struct file *file,
> fsnotify_modify(file);
>
> /* clear setuid/setgid flag after write */
> - if (inode->i_mode & (S_ISUID | S_ISGID))
> + if (should_remove_suid(dentry))
> kill_suid(dentry);
>
> if (stable) {
> --
> 1.9.0
>
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