On Sun, 29 Nov 2020, Serge E. Hallyn wrote: > Hi James, > > would you mind adding this to the security tree? (You can cherrypick > from > https://git.kernel.org/pub/scm/linux/kernel/git/sergeh/linux.git/commit/?h=2020-11-29/fix-nscaps > )
Sure. > > thanks, > -serge > > On Tue, Nov 17, 2020 at 08:09:59AM -0800, Andrew G. Morgan wrote: > > 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 > > > > > > > -- James Morris <jmor...@namei.org>
