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authorDavid Howells <dhowells@redhat.com>2008-08-14 11:37:28 +0100
committerJames Morris <jmorris@namei.org>2008-08-14 22:59:43 +1000
commit5cd9c58fbe9ec92b45b27e131719af4f2bd9eb40 (patch)
tree8573db001b4dc3c2ad97102dda42b841c40b5f6c /include/linux
parent8d0968abd03ec6b407df117adc773562386702fa (diff)
downloadlinux-2.6.38-lt-ux500-5cd9c58fbe9ec92b45b27e131719af4f2bd9eb40.tar.gz
security: Fix setting of PF_SUPERPRIV by __capable()
Fix the setting of PF_SUPERPRIV by __capable() as it could corrupt the flags the target process if that is not the current process and it is trying to change its own flags in a different way at the same time. __capable() is using neither atomic ops nor locking to protect t->flags. This patch removes __capable() and introduces has_capability() that doesn't set PF_SUPERPRIV on the process being queried. This patch further splits security_ptrace() in two: (1) security_ptrace_may_access(). This passes judgement on whether one process may access another only (PTRACE_MODE_ATTACH for ptrace() and PTRACE_MODE_READ for /proc), and takes a pointer to the child process. current is the parent. (2) security_ptrace_traceme(). This passes judgement on PTRACE_TRACEME only, and takes only a pointer to the parent process. current is the child. In Smack and commoncap, this uses has_capability() to determine whether the parent will be permitted to use PTRACE_ATTACH if normal checks fail. This does not set PF_SUPERPRIV. Two of the instances of __capable() actually only act on current, and so have been changed to calls to capable(). Of the places that were using __capable(): (1) The OOM killer calls __capable() thrice when weighing the killability of a process. All of these now use has_capability(). (2) cap_ptrace() and smack_ptrace() were using __capable() to check to see whether the parent was allowed to trace any process. As mentioned above, these have been split. For PTRACE_ATTACH and /proc, capable() is now used, and for PTRACE_TRACEME, has_capability() is used. (3) cap_safe_nice() only ever saw current, so now uses capable(). (4) smack_setprocattr() rejected accesses to tasks other than current just after calling __capable(), so the order of these two tests have been switched and capable() is used instead. (5) In smack_file_send_sigiotask(), we need to allow privileged processes to receive SIGIO on files they're manipulating. (6) In smack_task_wait(), we let a process wait for a privileged process, whether or not the process doing the waiting is privileged. I've tested this with the LTP SELinux and syscalls testscripts. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Serge Hallyn <serue@us.ibm.com> Acked-by: Casey Schaufler <casey@schaufler-ca.com> Acked-by: Andrew G. Morgan <morgan@kernel.org> Acked-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: James Morris <jmorris@namei.org>
Diffstat (limited to 'include/linux')
-rw-r--r--include/linux/capability.h15
-rw-r--r--include/linux/security.h39
2 files changed, 38 insertions, 16 deletions
diff --git a/include/linux/capability.h b/include/linux/capability.h
index 02673846d20..9d1fe30b6f6 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -503,8 +503,19 @@ extern const kernel_cap_t __cap_init_eff_set;
kernel_cap_t cap_set_effective(const kernel_cap_t pE_new);
-int capable(int cap);
-int __capable(struct task_struct *t, int cap);
+/**
+ * has_capability - Determine if a task has a superior capability available
+ * @t: The task in question
+ * @cap: The capability to be tested for
+ *
+ * Return true if the specified task has the given superior capability
+ * currently in effect, false if not.
+ *
+ * Note that this does not set PF_SUPERPRIV on the task.
+ */
+#define has_capability(t, cap) (security_capable((t), (cap)) == 0)
+
+extern int capable(int cap);
#endif /* __KERNEL__ */
diff --git a/include/linux/security.h b/include/linux/security.h
index fd96e7f8a6f..2ee5ecfb239 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -46,8 +46,8 @@ struct audit_krule;
*/
extern int cap_capable(struct task_struct *tsk, int cap);
extern int cap_settime(struct timespec *ts, struct timezone *tz);
-extern int cap_ptrace(struct task_struct *parent, struct task_struct *child,
- unsigned int mode);
+extern int cap_ptrace_may_access(struct task_struct *child, unsigned int mode);
+extern int cap_ptrace_traceme(struct task_struct *parent);
extern int cap_capget(struct task_struct *target, kernel_cap_t *effective, kernel_cap_t *inheritable, kernel_cap_t *permitted);
extern int cap_capset_check(struct task_struct *target, kernel_cap_t *effective, kernel_cap_t *inheritable, kernel_cap_t *permitted);
extern void cap_capset_set(struct task_struct *target, kernel_cap_t *effective, kernel_cap_t *inheritable, kernel_cap_t *permitted);
@@ -1157,17 +1157,24 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
* @alter contains the flag indicating whether changes are to be made.
* Return 0 if permission is granted.
*
- * @ptrace:
- * Check permission before allowing the @parent process to trace the
+ * @ptrace_may_access:
+ * Check permission before allowing the current process to trace the
* @child process.
* Security modules may also want to perform a process tracing check
* during an execve in the set_security or apply_creds hooks of
* binprm_security_ops if the process is being traced and its security
* attributes would be changed by the execve.
- * @parent contains the task_struct structure for parent process.
- * @child contains the task_struct structure for child process.
+ * @child contains the task_struct structure for the target process.
* @mode contains the PTRACE_MODE flags indicating the form of access.
* Return 0 if permission is granted.
+ * @ptrace_traceme:
+ * Check that the @parent process has sufficient permission to trace the
+ * current process before allowing the current process to present itself
+ * to the @parent process for tracing.
+ * The parent process will still have to undergo the ptrace_may_access
+ * checks before it is allowed to trace this one.
+ * @parent contains the task_struct structure for debugger process.
+ * Return 0 if permission is granted.
* @capget:
* Get the @effective, @inheritable, and @permitted capability sets for
* the @target process. The hook may also perform permission checking to
@@ -1287,8 +1294,8 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
struct security_operations {
char name[SECURITY_NAME_MAX + 1];
- int (*ptrace) (struct task_struct *parent, struct task_struct *child,
- unsigned int mode);
+ int (*ptrace_may_access) (struct task_struct *child, unsigned int mode);
+ int (*ptrace_traceme) (struct task_struct *parent);
int (*capget) (struct task_struct *target,
kernel_cap_t *effective,
kernel_cap_t *inheritable, kernel_cap_t *permitted);
@@ -1560,8 +1567,8 @@ extern struct dentry *securityfs_create_dir(const char *name, struct dentry *par
extern void securityfs_remove(struct dentry *dentry);
/* Security operations */
-int security_ptrace(struct task_struct *parent, struct task_struct *child,
- unsigned int mode);
+int security_ptrace_may_access(struct task_struct *child, unsigned int mode);
+int security_ptrace_traceme(struct task_struct *parent);
int security_capget(struct task_struct *target,
kernel_cap_t *effective,
kernel_cap_t *inheritable,
@@ -1742,11 +1749,15 @@ static inline int security_init(void)
return 0;
}
-static inline int security_ptrace(struct task_struct *parent,
- struct task_struct *child,
- unsigned int mode)
+static inline int security_ptrace_may_access(struct task_struct *child,
+ unsigned int mode)
+{
+ return cap_ptrace_may_access(child, mode);
+}
+
+static inline int security_ptrace_traceme(struct task_struct *child)
{
- return cap_ptrace(parent, child, mode);
+ return cap_ptrace_traceme(parent);
}
static inline int security_capget(struct task_struct *target,