Signed-off-by: Andrew G. Morgan <mor...@kernel.org>
On Tue, Nov 17, 2020 at 7:09 AM Serge E. Hallyn <se...@hallyn.com> wrote: > > Namespaced file capabilities were introduced in 8db6c34f1dbc . > When userspace reads an xattr for a namespaced capability, a > virtualized representation of it is returned if the caller is > in a user namespace owned by the capability's owning rootid. > The function which performs this virtualization was not hooked > up if CONFIG_SECURITY=n. Therefore in that case the original > xattr was shown instead of the virtualized one. > > To test this using libcap-bin (*1), > > $ v=$(mktemp) > $ unshare -Ur setcap cap_sys_admin-eip $v > $ unshare -Ur setcap -v cap_sys_admin-eip $v > /tmp/tmp.lSiIFRvt8Y: OK > > "setcap -v" verifies the values instead of setting them, and > will check whether the rootid value is set. Therefore, with > this bug un-fixed, and with CONFIG_SECURITY=n, setcap -v will > fail: > > $ v=$(mktemp) > $ unshare -Ur setcap cap_sys_admin=eip $v > $ unshare -Ur setcap -v cap_sys_admin=eip $v > nsowner[got=1000, want=0],/tmp/tmp.HHDiOOl9fY differs in [] > > Fix this bug by calling cap_inode_getsecurity() in > security_inode_getsecurity() instead of returning > -EOPNOTSUPP, when CONFIG_SECURITY=n. > > *1 - note, if libcap is too old for getcap to have the '-n' > option, then use verify-caps instead. > > Signed-off-by: Serge Hallyn <se...@hallyn.com> > Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1593431 > Cc: Hervé Guillemet <he...@guillemet.org> > Cc: Andrew G. Morgan <mor...@kernel.org> > Cc: Casey Schaufler <ca...@schaufler-ca.com> > --- > include/linux/security.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/linux/security.h b/include/linux/security.h > index bc2725491560..39642626a707 100644 > --- a/include/linux/security.h > +++ b/include/linux/security.h > @@ -869,7 +869,7 @@ static inline int security_inode_killpriv(struct dentry > *dentry) > > static inline int security_inode_getsecurity(struct inode *inode, const char > *name, void **buffer, bool alloc) > { > - return -EOPNOTSUPP; > + return cap_inode_getsecurity(inode, name, buffer, alloc); > } > > static inline int security_inode_setsecurity(struct inode *inode, const char > *name, const void *value, size_t size, int flags) > -- > 2.25.1 >
