Messages in this thread | | | Date | Thu, 7 Jan 2016 12:52:56 +0300 | From | Cyrill Gorcunov <> | Subject | Re: [PATCH 0/2] fix up {arg,env}_{start,end} vs prctl |
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On Wed, Jan 06, 2016 at 06:02:27AM +0100, Mateusz Guzik wrote: > An unprivileged user can trigger an oops on a kernel with > CONFIG_CHECKPOINT_RESTORE. > > proc_pid_cmdline_read takes mmap_sem for reading and obtains args + env > start/end values. These get sanity checked as follows: > BUG_ON(arg_start > arg_end); > BUG_ON(env_start > env_end); > > These can be changed by prctl_set_mm. Turns out also takes the semaphore for > reading, effectively rendering it useless. This results in:
Thanks a lot for catching it! You know I tried to escape taking sem for writing as long as I could so another option might be simply zap these BUG_ON and rather exit with -EINVAL. On the other hands modification under read-lock of course is not correct in terms of "general approach" but these members are special so I took a risk. Anyway,
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Thanks again.
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