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    Subject[PATCH 4.19 254/346] [SECURITY] fix namespaced fscaps when !CONFIG_SECURITY
    Date
    From: Serge Hallyn <shallyn@cisco.com>

    [ Upstream commit ed9b25d1970a4787ac6a39c2091e63b127ecbfc1 ]

    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.

    Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=209689
    Cc: Hervé Guillemet <herve@guillemet.org>
    Acked-by: Casey Schaufler <casey@schaufler-ca.com>
    Signed-off-by: Serge Hallyn <shallyn@cisco.com>
    Signed-off-by: Andrew G. Morgan <morgan@kernel.org>
    Signed-off-by: James Morris <jamorris@linux.microsoft.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    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 d2240605edc46..454cc963d1457 100644
    --- a/include/linux/security.h
    +++ b/include/linux/security.h
    @@ -787,7 +787,7 @@ 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)
    --
    2.27.0


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