Linus,
Please pull the for-linus branch from the git tree:
git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace.git
for-linus
HEAD: c70d9d809fdeecedb96972457ee45c49a232d97f ptrace: Properly initialize
ptracer_cred on fork
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.
Eric
Eric W. Biederman (1):
ptrace: Properly initialize ptracer_cred on fork
include/linux/ptrace.h | 7 +++++--
kernel/ptrace.c | 20 +++++++++++++-------
2 files changed, 18 insertions(+), 9 deletions(-)
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index 422bc2e4cb6a..ef3eb8bbfee4 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -54,7 +54,8 @@ extern int ptrace_request(struct task_struct *child, long
request,
unsigned long addr, unsigned long data);
extern void ptrace_notify(int exit_code);
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 exit_ptrace(struct task_struct *tracer, struct list_head *dead);
#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) {
child->ptrace = current->ptrace;
- __ptrace_link(child, current->parent);
+ __ptrace_link(child, current->parent, current->ptracer_cred);
if (child->ptrace & PT_SEIZED)
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);
}
+ else
+ child->ptracer_cred = NULL;
}
/**
diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index 266ddcc1d8bb..60f356d91060 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -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
* move it to the ptrace list.
*
* 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();
- child->ptracer_cred = get_cred(__task_cred(new_parent));
+ __ptrace_link(child, new_parent, __task_cred(new_parent));
rcu_read_unlock();
}
@@ -386,7 +392,7 @@ static int ptrace_attach(struct task_struct *task, long
request,
flags |= PT_SEIZED;
task->ptrace = flags;
- __ptrace_link(task, current);
+ ptrace_link(task, current);
/* SEIZE doesn't trap tracee on attach */
if (!seize)
@@ -459,7 +465,7 @@ static int ptrace_traceme(void)
*/
if (!ret && !(current->real_parent->flags & PF_EXITING)) {
current->ptrace = PT_PTRACED;
- __ptrace_link(current, current->real_parent);
+ ptrace_link(current, current->real_parent);
}
}
write_unlock_irq(&tasklist_lock);
--
2.10.1
