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Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 

Pull ptrace fix from Eric Biederman:
 "This fixes a brown paper bag bug. When I fixed the ptrace interaction
  with user namespaces I added a new field ptracer_cred in struct_task
  and I failed to properly initialize it on fork.

  This dangling pointer wound up breaking runing setuid applications run
  from the enlightenment window manager.

  As this is the worst sort of bug. A regression breaking user space for
  no good reason let's get this fixed"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
  ptrace: Properly initialize ptracer_cred on fork
This commit is contained in:
Linus Torvalds 2017-05-24 08:28:59 -07:00
parent 590d4b333d c70d9d809f
commit 2426125ab4
2 changed files with 18 additions and 9 deletions
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7
include/linux/ptrace.h
View File

@ -54,7 +54,8 @@ extern int ptrace_request(struct task_struct *child, long request,
unsigned long addr, unsigned long data); unsigned long addr, unsigned long data);
extern void ptrace_notify(int exit_code); extern void ptrace_notify(int exit_code);
extern void __ptrace_link(struct task_struct *child, extern void __ptrace_link(struct task_struct *child,
struct task_struct *new_parent); struct task_struct *new_parent,
const struct cred *ptracer_cred);
extern void __ptrace_unlink(struct task_struct *child); extern void __ptrace_unlink(struct task_struct *child);
extern void exit_ptrace(struct task_struct *tracer, struct list_head *dead); extern void exit_ptrace(struct task_struct *tracer, struct list_head *dead);
#define PTRACE_MODE_READ 0x01 #define PTRACE_MODE_READ 0x01
@ -206,7 +207,7 @@ static inline void ptrace_init_task(struct task_struct *child, bool ptrace)
if (unlikely(ptrace) && current->ptrace) { if (unlikely(ptrace) && current->ptrace) {
child->ptrace = current->ptrace; child->ptrace = current->ptrace;
__ptrace_link(child, current->parent); __ptrace_link(child, current->parent, current->ptracer_cred);
if (child->ptrace & PT_SEIZED) if (child->ptrace & PT_SEIZED)
task_set_jobctl_pending(child, JOBCTL_TRAP_STOP); task_set_jobctl_pending(child, JOBCTL_TRAP_STOP);
@ -215,6 +216,8 @@ static inline void ptrace_init_task(struct task_struct *child, bool ptrace)
set_tsk_thread_flag(child, TIF_SIGPENDING); set_tsk_thread_flag(child, TIF_SIGPENDING);
} }
else
child->ptracer_cred = NULL;
} }
/** /**

20
kernel/ptrace.c
View File

@ -60,19 +60,25 @@ int ptrace_access_vm(struct task_struct *tsk, unsigned long addr,
} }
void __ptrace_link(struct task_struct *child, struct task_struct *new_parent,
const struct cred *ptracer_cred)
{
BUG_ON(!list_empty(&child->ptrace_entry));
list_add(&child->ptrace_entry, &new_parent->ptraced);
child->parent = new_parent;
child->ptracer_cred = get_cred(ptracer_cred);
}
/* /*
* ptrace a task: make the debugger its new parent and * ptrace a task: make the debugger its new parent and
* move it to the ptrace list. * move it to the ptrace list.
* *
* Must be called with the tasklist lock write-held. * Must be called with the tasklist lock write-held.
*/ */
void __ptrace_link(struct task_struct *child, struct task_struct *new_parent) static void ptrace_link(struct task_struct *child, struct task_struct *new_parent)
{ {
BUG_ON(!list_empty(&child->ptrace_entry));
list_add(&child->ptrace_entry, &new_parent->ptraced);
child->parent = new_parent;
rcu_read_lock(); rcu_read_lock();
child->ptracer_cred = get_cred(__task_cred(new_parent)); __ptrace_link(child, new_parent, __task_cred(new_parent));
rcu_read_unlock(); rcu_read_unlock();
} }
@ -386,7 +392,7 @@ static int ptrace_attach(struct task_struct *task, long request,
flags |= PT_SEIZED; flags |= PT_SEIZED;
task->ptrace = flags; task->ptrace = flags;
__ptrace_link(task, current); ptrace_link(task, current);
/* SEIZE doesn't trap tracee on attach */ /* SEIZE doesn't trap tracee on attach */
if (!seize) if (!seize)
@ -459,7 +465,7 @@ static int ptrace_traceme(void)
*/ */
if (!ret && !(current->real_parent->flags & PF_EXITING)) { if (!ret && !(current->real_parent->flags & PF_EXITING)) {
current->ptrace = PT_PTRACED; current->ptrace = PT_PTRACED;
__ptrace_link(current, current->real_parent); ptrace_link(current, current->real_parent);
} }
} }
write_unlock_irq(&tasklist_lock); write_unlock_irq(&tasklist_lock);