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)