Add 64-bit capability support to the kernel
The patch supports legacy (32-bit) capability userspace, and where possible
translates 32-bit capabilities to/from userspace and the VFS to 64-bit
kernel space capabilities. If a capability set cannot be compressed into
32-bits for consumption by user space, the system call fails, with -ERANGE.
FWIW libcap-2.00 supports this change (and earlier capability formats)
http://www.kernel.org/pub/linux/libs/security/linux-privs/kernel-2.6/
[akpm@linux-foundation.org: coding-syle fixes]
[akpm@linux-foundation.org: use get_task_comm()]
[ezk@cs.sunysb.edu: build fix]
[akpm@linux-foundation.org: do not initialise statics to 0 or NULL]
[akpm@linux-foundation.org: unused var]
[serue@us.ibm.com: export __cap_ symbols]
Signed-off-by: Andrew G. Morgan <morgan@kernel.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: James Morris <jmorris@namei.org>
Cc: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/capability.c b/kernel/capability.c
index efbd9cd..39e8193 100644
--- a/kernel/capability.c
+++ b/kernel/capability.c
@@ -22,6 +22,37 @@
static DEFINE_SPINLOCK(task_capability_lock);
/*
+ * Leveraged for setting/resetting capabilities
+ */
+
+const kernel_cap_t __cap_empty_set = CAP_EMPTY_SET;
+const kernel_cap_t __cap_full_set = CAP_FULL_SET;
+const kernel_cap_t __cap_init_eff_set = CAP_INIT_EFF_SET;
+
+EXPORT_SYMBOL(__cap_empty_set);
+EXPORT_SYMBOL(__cap_full_set);
+EXPORT_SYMBOL(__cap_init_eff_set);
+
+/*
+ * More recent versions of libcap are available from:
+ *
+ * http://www.kernel.org/pub/linux/libs/security/linux-privs/
+ */
+
+static void warn_legacy_capability_use(void)
+{
+ static int warned;
+ if (!warned) {
+ char name[sizeof(current->comm)];
+
+ printk(KERN_INFO "warning: `%s' uses 32-bit capabilities"
+ " (legacy support in use)\n",
+ get_task_comm(name, current));
+ warned = 1;
+ }
+}
+
+/*
* For sys_getproccap() and sys_setproccap(), any of the three
* capability set pointers may be NULL -- indicating that that set is
* uninteresting and/or not to be changed.
@@ -42,12 +73,21 @@
pid_t pid;
__u32 version;
struct task_struct *target;
- struct __user_cap_data_struct data;
+ unsigned tocopy;
+ kernel_cap_t pE, pI, pP;
if (get_user(version, &header->version))
return -EFAULT;
- if (version != _LINUX_CAPABILITY_VERSION) {
+ switch (version) {
+ case _LINUX_CAPABILITY_VERSION_1:
+ warn_legacy_capability_use();
+ tocopy = _LINUX_CAPABILITY_U32S_1;
+ break;
+ case _LINUX_CAPABILITY_VERSION_2:
+ tocopy = _LINUX_CAPABILITY_U32S_2;
+ break;
+ default:
if (put_user(_LINUX_CAPABILITY_VERSION, &header->version))
return -EFAULT;
return -EINVAL;
@@ -71,14 +111,47 @@
} else
target = current;
- ret = security_capget(target, &data.effective, &data.inheritable, &data.permitted);
+ ret = security_capget(target, &pE, &pI, &pP);
out:
read_unlock(&tasklist_lock);
spin_unlock(&task_capability_lock);
- if (!ret && copy_to_user(dataptr, &data, sizeof data))
- return -EFAULT;
+ if (!ret) {
+ struct __user_cap_data_struct kdata[_LINUX_CAPABILITY_U32S];
+ unsigned i;
+
+ for (i = 0; i < tocopy; i++) {
+ kdata[i].effective = pE.cap[i];
+ kdata[i].permitted = pP.cap[i];
+ kdata[i].inheritable = pI.cap[i];
+ }
+
+ /*
+ * Note, in the case, tocopy < _LINUX_CAPABILITY_U32S,
+ * we silently drop the upper capabilities here. This
+ * has the effect of making older libcap
+ * implementations implicitly drop upper capability
+ * bits when they perform a: capget/modify/capset
+ * sequence.
+ *
+ * This behavior is considered fail-safe
+ * behavior. Upgrading the application to a newer
+ * version of libcap will enable access to the newer
+ * capabilities.
+ *
+ * An alternative would be to return an error here
+ * (-ERANGE), but that causes legacy applications to
+ * unexpectidly fail; the capget/modify/capset aborts
+ * before modification is attempted and the application
+ * fails.
+ */
+
+ if (copy_to_user(dataptr, kdata, tocopy
+ * sizeof(struct __user_cap_data_struct))) {
+ return -EFAULT;
+ }
+ }
return ret;
}
@@ -167,6 +240,8 @@
*/
asmlinkage long sys_capset(cap_user_header_t header, const cap_user_data_t data)
{
+ struct __user_cap_data_struct kdata[_LINUX_CAPABILITY_U32S];
+ unsigned i, tocopy;
kernel_cap_t inheritable, permitted, effective;
__u32 version;
struct task_struct *target;
@@ -176,7 +251,15 @@
if (get_user(version, &header->version))
return -EFAULT;
- if (version != _LINUX_CAPABILITY_VERSION) {
+ switch (version) {
+ case _LINUX_CAPABILITY_VERSION_1:
+ warn_legacy_capability_use();
+ tocopy = _LINUX_CAPABILITY_U32S_1;
+ break;
+ case _LINUX_CAPABILITY_VERSION_2:
+ tocopy = _LINUX_CAPABILITY_U32S_2;
+ break;
+ default:
if (put_user(_LINUX_CAPABILITY_VERSION, &header->version))
return -EFAULT;
return -EINVAL;
@@ -188,10 +271,22 @@
if (pid && pid != task_pid_vnr(current) && !capable(CAP_SETPCAP))
return -EPERM;
- if (copy_from_user(&effective, &data->effective, sizeof(effective)) ||
- copy_from_user(&inheritable, &data->inheritable, sizeof(inheritable)) ||
- copy_from_user(&permitted, &data->permitted, sizeof(permitted)))
+ if (copy_from_user(&kdata, data, tocopy
+ * sizeof(struct __user_cap_data_struct))) {
return -EFAULT;
+ }
+
+ for (i = 0; i < tocopy; i++) {
+ effective.cap[i] = kdata[i].effective;
+ permitted.cap[i] = kdata[i].permitted;
+ inheritable.cap[i] = kdata[i].inheritable;
+ }
+ while (i < _LINUX_CAPABILITY_U32S) {
+ effective.cap[i] = 0;
+ permitted.cap[i] = 0;
+ inheritable.cap[i] = 0;
+ i++;
+ }
spin_lock(&task_capability_lock);
read_lock(&tasklist_lock);
