From 5cd9c58fbe9ec92b45b27e131719af4f2bd9eb40 Mon Sep 17 00:00:00 2001 From: David Howells Date: Thu, 14 Aug 2008 11:37:28 +0100 Subject: 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 Acked-by: Serge Hallyn Acked-by: Casey Schaufler Acked-by: Andrew G. Morgan Acked-by: Al Viro Signed-off-by: James Morris --- security/selinux/hooks.c | 25 ++++++++++++++++++------- 1 file changed, 18 insertions(+), 7 deletions(-) (limited to 'security/selinux') diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 3ae9bec5a50..03fc6a81ae3 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -1738,24 +1738,34 @@ static inline u32 file_to_av(struct file *file) /* Hook functions begin here. */ -static int selinux_ptrace(struct task_struct *parent, - struct task_struct *child, - unsigned int mode) +static int selinux_ptrace_may_access(struct task_struct *child, + unsigned int mode) { int rc; - rc = secondary_ops->ptrace(parent, child, mode); + rc = secondary_ops->ptrace_may_access(child, mode); if (rc) return rc; if (mode == PTRACE_MODE_READ) { - struct task_security_struct *tsec = parent->security; + struct task_security_struct *tsec = current->security; struct task_security_struct *csec = child->security; return avc_has_perm(tsec->sid, csec->sid, SECCLASS_FILE, FILE__READ, NULL); } - return task_has_perm(parent, child, PROCESS__PTRACE); + return task_has_perm(current, child, PROCESS__PTRACE); +} + +static int selinux_ptrace_traceme(struct task_struct *parent) +{ + int rc; + + rc = secondary_ops->ptrace_traceme(parent); + if (rc) + return rc; + + return task_has_perm(parent, current, PROCESS__PTRACE); } static int selinux_capget(struct task_struct *target, kernel_cap_t *effective, @@ -5346,7 +5356,8 @@ static int selinux_key_getsecurity(struct key *key, char **_buffer) static struct security_operations selinux_ops = { .name = "selinux", - .ptrace = selinux_ptrace, + .ptrace_may_access = selinux_ptrace_may_access, + .ptrace_traceme = selinux_ptrace_traceme, .capget = selinux_capget, .capset_check = selinux_capset_check, .capset_set = selinux_capset_set, -- cgit v1.2.3