On Tue, 2016-06-21 at 10:37 +0100, Pengfei Wang wrote: > > > > 在 2016年6月20日，下午8:18，Oleg Nesterov <[email protected]> 写道： > > > > Not that I understand this report, but > > > > On 06/20, Richard Guy Briggs wrote: > > > > > > This function is only ever called by __audit_free(), which is only ever > > > called on failure of task creation or on exit of the task, so in neither > > > case can anything else change it. > > > > How so? > > > > Another thread or CLONE_VM task or /proc/pid/mem can change the user-space > > memory in parallel. > > > > Oleg. > > > Exactly, by saying “change the data”, I mean the modification from > malicious users with crafted operations on the user space memory > directly, rather than the normal operations within the audit > subsystem in Linux. Moreover, since the copy operations from the user > space are not protected by any locks or synchronization primitives, > changing the data under race condition is feasible I think. Besides, > there isn’t any visible checking step in the code to guarantee the > consistency between the two copy operations. > > Here I would like to figure out what the consequences really are once > the data is changed between the two copy operations, such as changing > a none-control string to a control string but process it as a none- > control string that has no control chars. I think problems will > happen.
So far as userland can see, kernel log lines are separated by newlines. If we fail to escape a newline, that makes it possible to inject arbitrary log lines into the kernel log, which may be misleading to the administrator or to software parsing the log. Ben. -- Ben Hutchings [W]e found...that it wasn't as easy to get programs right as we had thought. ... I realized that a large part of my life from then on was going to be spent in finding mistakes in my own programs. - Maurice Wilkes, 1949
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