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authorDavid Howells <dhowells@redhat.com>2008-08-14 06:37:28 -0400
committerJames Morris <jmorris@namei.org>2008-08-14 08:59:43 -0400
commit5cd9c58fbe9ec92b45b27e131719af4f2bd9eb40 (patch)
tree8573db001b4dc3c2ad97102dda42b841c40b5f6c /security/commoncap.c
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/commoncap.c')
-rw-r--r--security/commoncap.c24
1 files changed, 17 insertions, 7 deletions
diff --git a/security/commoncap.c b/security/commoncap.c
index 4afbece37a08..e4c4b3fc0c04 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -63,14 +63,24 @@ int cap_settime(struct timespec *ts, struct timezone *tz)
63 return 0; 63 return 0;
64} 64}
65 65
66int cap_ptrace (struct task_struct *parent, struct task_struct *child, 66int cap_ptrace_may_access(struct task_struct *child, unsigned int mode)
67 unsigned int mode)
68{ 67{
69 /* Derived from arch/i386/kernel/ptrace.c:sys_ptrace. */ 68 /* Derived from arch/i386/kernel/ptrace.c:sys_ptrace. */
70 if (!cap_issubset(child->cap_permitted, parent->cap_permitted) && 69 if (cap_issubset(child->cap_permitted, current->cap_permitted))
71 !__capable(parent, CAP_SYS_PTRACE)) 70 return 0;
72 return -EPERM; 71 if (capable(CAP_SYS_PTRACE))
73 return 0; 72 return 0;
73 return -EPERM;
74}
75
76int cap_ptrace_traceme(struct task_struct *parent)
77{
78 /* Derived from arch/i386/kernel/ptrace.c:sys_ptrace. */
79 if (cap_issubset(current->cap_permitted, parent->cap_permitted))
80 return 0;
81 if (has_capability(parent, CAP_SYS_PTRACE))
82 return 0;
83 return -EPERM;
74} 84}
75 85
76int cap_capget (struct task_struct *target, kernel_cap_t *effective, 86int cap_capget (struct task_struct *target, kernel_cap_t *effective,
@@ -534,7 +544,7 @@ int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid,
534static inline int cap_safe_nice(struct task_struct *p) 544static inline int cap_safe_nice(struct task_struct *p)
535{ 545{
536 if (!cap_issubset(p->cap_permitted, current->cap_permitted) && 546 if (!cap_issubset(p->cap_permitted, current->cap_permitted) &&
537 !__capable(current, CAP_SYS_NICE)) 547 !capable(CAP_SYS_NICE))
538 return -EPERM; 548 return -EPERM;
539 return 0; 549 return 0;
540} 550}