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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 /security/smack
parent8d0968abd03ec6b407df117adc773562386702fa (diff)
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 'security/smack')
-rw-r--r--security/smack/smack_lsm.c49
1 files changed, 34 insertions, 15 deletions
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 1b40e558f983..87d75417ea93 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -87,27 +87,46 @@ struct inode_smack *new_inode_smack(char *smack)
*/
/**
- * smack_ptrace - Smack approval on ptrace
- * @ptp: parent task pointer
+ * smack_ptrace_may_access - Smack approval on PTRACE_ATTACH
* @ctp: child task pointer
*
* Returns 0 if access is OK, an error code otherwise
*
* Do the capability checks, and require read and write.
*/
-static int smack_ptrace(struct task_struct *ptp, struct task_struct *ctp,
- unsigned int mode)
+static int smack_ptrace_may_access(struct task_struct *ctp, unsigned int mode)
{
int rc;
- rc = cap_ptrace(ptp, ctp, mode);
+ rc = cap_ptrace_may_access(ctp, mode);
if (rc != 0)
return rc;
- rc = smk_access(ptp->security, ctp->security, MAY_READWRITE);
- if (rc != 0 && __capable(ptp, CAP_MAC_OVERRIDE))
+ rc = smk_access(current->security, ctp->security, MAY_READWRITE);
+ if (rc != 0 && capable(CAP_MAC_OVERRIDE))
return 0;
+ return rc;
+}
+
+/**
+ * smack_ptrace_traceme - Smack approval on PTRACE_TRACEME
+ * @ptp: parent task pointer
+ *
+ * Returns 0 if access is OK, an error code otherwise
+ *
+ * Do the capability checks, and require read and write.
+ */
+static int smack_ptrace_traceme(struct task_struct *ptp)
+{
+ int rc;
+
+ rc = cap_ptrace_traceme(ptp);
+ if (rc != 0)
+ return rc;
+ rc = smk_access(ptp->security, current->security, MAY_READWRITE);
+ if (rc != 0 && has_capability(ptp, CAP_MAC_OVERRIDE))
+ return 0;
return rc;
}
@@ -923,7 +942,7 @@ static int smack_file_send_sigiotask(struct task_struct *tsk,
*/
file = container_of(fown, struct file, f_owner);
rc = smk_access(file->f_security, tsk->security, MAY_WRITE);
- if (rc != 0 && __capable(tsk, CAP_MAC_OVERRIDE))
+ if (rc != 0 && has_capability(tsk, CAP_MAC_OVERRIDE))
return 0;
return rc;
}
@@ -1164,12 +1183,12 @@ static int smack_task_wait(struct task_struct *p)
* account for the smack labels having gotten to
* be different in the first place.
*
- * This breaks the strict subjet/object access
+ * This breaks the strict subject/object access
* control ideal, taking the object's privilege
* state into account in the decision as well as
* the smack value.
*/
- if (capable(CAP_MAC_OVERRIDE) || __capable(p, CAP_MAC_OVERRIDE))
+ if (capable(CAP_MAC_OVERRIDE) || has_capability(p, CAP_MAC_OVERRIDE))
return 0;
return rc;
@@ -2016,9 +2035,6 @@ static int smack_setprocattr(struct task_struct *p, char *name,
{
char *newsmack;
- if (!__capable(p, CAP_MAC_ADMIN))
- return -EPERM;
-
/*
* Changing another process' Smack value is too dangerous
* and supports no sane use case.
@@ -2026,6 +2042,9 @@ static int smack_setprocattr(struct task_struct *p, char *name,
if (p != current)
return -EPERM;
+ if (!capable(CAP_MAC_ADMIN))
+ return -EPERM;
+
if (value == NULL || size == 0 || size >= SMK_LABELLEN)
return -EINVAL;
@@ -2552,7 +2571,8 @@ static void smack_release_secctx(char *secdata, u32 seclen)
struct security_operations smack_ops = {
.name = "smack",
- .ptrace = smack_ptrace,
+ .ptrace_may_access = smack_ptrace_may_access,
+ .ptrace_traceme = smack_ptrace_traceme,
.capget = cap_capget,
.capset_check = cap_capset_check,
.capset_set = cap_capset_set,
@@ -2729,4 +2749,3 @@ static __init int smack_init(void)
* all processes and objects when they are created.
*/
security_initcall(smack_init);
-