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tracehook: tracehook_tracer_task

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This adds the tracehook_tracer_task() hook to consolidate all forms of
"Who is using ptrace on me?" logic.  This is used for "TracerPid:" in
/proc and for permission checks.  We also clean up the selinux code the
called an identical accessor.

Signed-off-by: Roland McGrath <roland@redhat.com>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Reviewed-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Roland McGrath 2008-07-25 19:45:49 -07:00 committed by Linus Torvalds
parent dae33574dc
commit 0d094efeb1
4 changed files with 37 additions and 25 deletions
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9
fs/proc/array.c
View file

@ -80,6 +80,7 @@
#include <linux/delayacct.h>
#include <linux/seq_file.h>
#include <linux/pid_namespace.h>
#include <linux/tracehook.h>
#include <asm/pgtable.h>
#include <asm/processor.h>
@ -168,8 +169,12 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns,
rcu_read_lock();
ppid = pid_alive(p) ?
task_tgid_nr_ns(rcu_dereference(p->real_parent), ns) : 0;
tpid = pid_alive(p) && p->ptrace ?
task_pid_nr_ns(rcu_dereference(p->parent), ns) : 0;
tpid = 0;
if (pid_alive(p)) {
struct task_struct *tracer = tracehook_tracer_task(p);
if (tracer)
tpid = task_pid_nr_ns(tracer, ns);
}
seq_printf(m,
"State:\t%s\n"
"Tgid:\t%d\n"

13
fs/proc/base.c
View file

@ -69,6 +69,7 @@
#include <linux/mount.h>
#include <linux/security.h>
#include <linux/ptrace.h>
#include <linux/tracehook.h>
#include <linux/cgroup.h>
#include <linux/cpuset.h>
#include <linux/audit.h>
@ -231,10 +232,14 @@ static int check_mem_permission(struct task_struct *task)
* If current is actively ptrace'ing, and would also be
* permitted to freshly attach with ptrace now, permit it.
*/
if (task->parent == current && (task->ptrace & PT_PTRACED) &&
task_is_stopped_or_traced(task) &&
ptrace_may_access(task, PTRACE_MODE_ATTACH))
return 0;
if (task_is_stopped_or_traced(task)) {
int match;
rcu_read_lock();
match = (tracehook_tracer_task(task) == current);
rcu_read_unlock();
if (match && ptrace_may_access(task, PTRACE_MODE_ATTACH))
return 0;
}
/*
* Noone else is allowed.

18
include/linux/tracehook.h
View file

@ -72,6 +72,24 @@ static inline int tracehook_unsafe_exec(struct task_struct *task)
return unsafe;
}
/**
* tracehook_tracer_task - return the task that is tracing the given task
* @tsk: task to consider
*
* Returns NULL if noone is tracing @task, or the &struct task_struct
* pointer to its tracer.
*
* Must called under rcu_read_lock(). The pointer returned might be kept
* live only by RCU. During exec, this may be called with task_lock()
* held on @task, still held from when tracehook_unsafe_exec() was called.
*/
static inline struct task_struct *tracehook_tracer_task(struct task_struct *tsk)
{
if (task_ptrace(tsk) & PT_PTRACED)
return rcu_dereference(tsk->parent);
return NULL;
}
/**
* tracehook_report_exec - a successful exec was completed
* @fmt: &struct linux_binfmt that performed the exec

22
security/selinux/hooks.c
View file

@ -25,7 +25,7 @@
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/ptrace.h>
#include <linux/tracehook.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/security.h>
@ -1971,22 +1971,6 @@ static int selinux_vm_enough_memory(struct mm_struct *mm, long pages)
return __vm_enough_memory(mm, pages, cap_sys_admin);
}
/**
* task_tracer_task - return the task that is tracing the given task
* @task: task to consider
*
* Returns NULL if noone is tracing @task, or the &struct task_struct
* pointer to its tracer.
*
* Must be called under rcu_read_lock().
*/
static struct task_struct *task_tracer_task(struct task_struct *task)
{
if (task->ptrace & PT_PTRACED)
return rcu_dereference(task->parent);
return NULL;
}
/* binprm security operations */
static int selinux_bprm_alloc_security(struct linux_binprm *bprm)
@ -2238,7 +2222,7 @@ static void selinux_bprm_apply_creds(struct linux_binprm *bprm, int unsafe)
u32 ptsid = 0;
rcu_read_lock();
tracer = task_tracer_task(current);
tracer = tracehook_tracer_task(current);
if (likely(tracer != NULL)) {
sec = tracer->security;
ptsid = sec->sid;
@ -5247,7 +5231,7 @@ static int selinux_setprocattr(struct task_struct *p,
Otherwise, leave SID unchanged and fail. */
task_lock(p);
rcu_read_lock();
tracer = task_tracer_task(p);
tracer = tracehook_tracer_task(p);
if (tracer != NULL) {
struct task_security_struct *ptsec = tracer->security;
u32 ptsid = ptsec->sid;