Messages in this thread Patch in this message | | | Date | Sun, 11 Aug 2013 19:53:25 +0200 | From | Oleg Nesterov <> | Subject | [PATCH] __ptrace_may_access() should not deny sub-threads |
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From: Mark Grondona <mgrondona@llnl.gov>
__ptrace_may_access() checks get_dumpable/ptrace_has_cap/etc if task != current, this can can lead to surprising results.
For example, a sub-thread can't readlink("/proc/self/exe") if the executable is not readable. setup_new_exec()->would_dump() notices that inode_permission(MAY_READ) fails and then it does set_dumpable(suid_dumpable). After that get_dumpable() fails.
(It is not clear why proc_pid_readlink() checks get_dumpable(), perhaps we could add PTRACE_MODE_NODUMPABLE)
Change __ptrace_may_access() to use same_thread_group() instead of "task == current". Any security check is pointless when the tasks share the same ->mm.
Signed-off-by: Mark Grondona <mgrondona@llnl.gov> Signed-off-by: Ben Woodard <woodard@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> --- kernel/ptrace.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/kernel/ptrace.c b/kernel/ptrace.c index a146ee3..dd562e9 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -236,7 +236,7 @@ static int __ptrace_may_access(struct task_struct *task, unsigned int mode) */ int dumpable = 0; /* Don't let security modules deny introspection */ - if (task == current) + if (same_thread_group(task, current)) return 0; rcu_read_lock(); tcred = __task_cred(task); -- 1.5.5.1
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