114 lines
3.9 KiB
Diff
114 lines
3.9 KiB
Diff
From: "Eric W. Biederman" <ebiederm@xmission.com>
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Date: Mon, 22 May 2017 16:04:48 -0500
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Subject: [PATCH] ptrace: Properly initialize ptracer_cred on fork
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Message-ID: <877f18txfz.fsf_-_@xmission.com>
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Patch-mainline: Submitted, LKML
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References: bsc#1040041
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When I introduced ptracer_cred I failed to consider the weirdness of
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fork where the task_struct copies the old value by default. This
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winds up leaving ptracer_cred set even when a process forks and
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the child process does not wind up being ptraced.
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Because ptracer_cred is not set on non-ptraced processes whose
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parents were ptraced this has broken the ability of the enlightenment
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window manager to start setuid children.
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Fix this by properly initializing ptracer_cred in ptrace_init_task
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This must be done with a little bit of care to preserve the current value
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of ptracer_cred when ptrace carries through fork. Re-reading the
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ptracer_cred from the ptracing process at this point is inconsistent
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with how PT_PTRACE_CAP has been maintained all of these years.
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Fixes: 64b875f7ac8a ("ptrace: Capture the ptracer's creds not PT_PTRACE_CAP")
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Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
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Signed-off-by: Takashi Iwai <tiwai@suse.de>
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---
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include/linux/ptrace.h | 7 +++++--
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kernel/ptrace.c | 20 +++++++++++++-------
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2 files changed, 18 insertions(+), 9 deletions(-)
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--- a/include/linux/ptrace.h
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+++ b/include/linux/ptrace.h
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@@ -54,7 +54,8 @@ extern int ptrace_request(struct task_st
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unsigned long addr, unsigned long data);
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extern void ptrace_notify(int exit_code);
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extern void __ptrace_link(struct task_struct *child,
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- struct task_struct *new_parent);
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+ struct task_struct *new_parent,
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+ const struct cred *ptracer_cred);
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extern void __ptrace_unlink(struct task_struct *child);
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extern void exit_ptrace(struct task_struct *tracer, struct list_head *dead);
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#define PTRACE_MODE_READ 0x01
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@@ -206,7 +207,7 @@ static inline void ptrace_init_task(stru
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if (unlikely(ptrace) && current->ptrace) {
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child->ptrace = current->ptrace;
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- __ptrace_link(child, current->parent);
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+ __ptrace_link(child, current->parent, current->ptracer_cred);
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if (child->ptrace & PT_SEIZED)
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task_set_jobctl_pending(child, JOBCTL_TRAP_STOP);
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@@ -215,6 +216,8 @@ static inline void ptrace_init_task(stru
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set_tsk_thread_flag(child, TIF_SIGPENDING);
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}
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+ else
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+ child->ptracer_cred = NULL;
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}
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/**
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--- a/kernel/ptrace.c
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+++ b/kernel/ptrace.c
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@@ -60,19 +60,25 @@ int ptrace_access_vm(struct task_struct
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}
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+void __ptrace_link(struct task_struct *child, struct task_struct *new_parent,
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+ const struct cred *ptracer_cred)
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+{
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+ BUG_ON(!list_empty(&child->ptrace_entry));
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+ list_add(&child->ptrace_entry, &new_parent->ptraced);
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+ child->parent = new_parent;
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+ child->ptracer_cred = get_cred(ptracer_cred);
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+}
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+
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/*
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* ptrace a task: make the debugger its new parent and
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* move it to the ptrace list.
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*
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* Must be called with the tasklist lock write-held.
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*/
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-void __ptrace_link(struct task_struct *child, struct task_struct *new_parent)
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+static void ptrace_link(struct task_struct *child, struct task_struct *new_parent)
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{
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- BUG_ON(!list_empty(&child->ptrace_entry));
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- list_add(&child->ptrace_entry, &new_parent->ptraced);
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- child->parent = new_parent;
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rcu_read_lock();
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- child->ptracer_cred = get_cred(__task_cred(new_parent));
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+ __ptrace_link(child, new_parent, __task_cred(new_parent));
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rcu_read_unlock();
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}
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@@ -386,7 +392,7 @@ static int ptrace_attach(struct task_str
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flags |= PT_SEIZED;
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task->ptrace = flags;
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- __ptrace_link(task, current);
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+ ptrace_link(task, current);
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/* SEIZE doesn't trap tracee on attach */
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if (!seize)
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@@ -459,7 +465,7 @@ static int ptrace_traceme(void)
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*/
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if (!ret && !(current->real_parent->flags & PF_EXITING)) {
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current->ptrace = PT_PTRACED;
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- __ptrace_link(current, current->real_parent);
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+ ptrace_link(current, current->real_parent);
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}
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}
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write_unlock_irq(&tasklist_lock);
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