From: Mark Grondona <mgrond...@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 <mgrond...@llnl.gov> Signed-off-by: Ben Woodard <wood...@redhat.com> Signed-off-by: Oleg Nesterov <o...@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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/