On Mon, Nov 5, 2018 at 8:22 PM Mark Salyzyn <salyzyn@xxxxxxxxxxx> wrote: > > overlayfs: check CAP_DAC_READ_SEARCH before issuing exportfs_decode_fh > > Assumption never checked, should fail if the mounter creds are not > sufficient. > > overlayfs: override_creds=off option bypass creator_cred > > By default, all access to the upper, lower and work directories is the > recorded mounter's MAC and DAC credentials. The incoming accesses are > checked against the caller's credentials. > > If the principles of least privilege are applied, the mounter's > credentials might not overlap the credentials of the caller's when > accessing the overlayfs filesystem. For example, a file that a lower > DAC privileged caller can execute, is MAC denied to the generally > higher DAC privileged mounter, to prevent an attack vector. > > We add the option to turn off override_creds in the mount options; all > subsequent operations after mount on the filesystem will be only the > caller's credentials. The module boolean parameter and mount option > override_creds is also added as a presence check for this "feature", > existence of /sys/module/overlay/parameters/overlay_creds > > Signed-off-by: Mark Salyzyn <salyzyn@xxxxxxxxxxx> > Cc: Miklos Szeredi <miklos@xxxxxxxxxx> > Cc: Jonathan Corbet <corbet@xxxxxxx> > Cc: Vivek Goyal <vgoyal@xxxxxxxxxx> > Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx> > Cc: Amir Goldstein <amir73il@xxxxxxxxx> > Cc: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> > Cc: Stephen Smalley <sds@xxxxxxxxxxxxx> > Cc: linux-unionfs@xxxxxxxxxxxxxxx > Cc: linux-doc@xxxxxxxxxxxxxxx > Cc: linux-kernel@xxxxxxxxxxxxxxx > > v2: > - Forward port changed attr to stat, resulting in a build error. > - altered commit message. > > v3: > - Change name from caller_credentials / creator_credentials to the > boolean override_creds. > - Changed from creator to mounter credentials. > - Updated and fortified the documentation. > - Added CONFIG_OVERLAY_FS_OVERRIDE_CREDS > > v4: > - spelling and grammar errors in text > > v5: > - beefed up the caveats in the Documentation > - Is dependent on > "overlayfs: check CAP_DAC_READ_SEARCH before issuing exportfs_decode_fh" > "overlayfs: check CAP_MKNOD before issuing vfs_whiteout" > - Added prwarn when override_creds=off > > v6: > - Drop CONFIG_OVERLAY_FS_OVERRIDE_CREDS. > - Do better with the documentation, drop rationalizations. > - pr_warn message adjusted to report consequences. For future reference, the cover letter is meant for introduction, not for concatenating all commit messages... Not sure how you generated this text. I think you were looking for git format-patch --cover. Anyway, IMO, having the patch revision in the cover letter is sufficient and you needn't bother with patch revision in every single patch, unless there is a good reason. Thanks, Amir.
