Ok, so the obvious question is what is at that kernel address? On February 24, 2014 8:34:30 AM PST, Vince Weaver <vincent.wea...@maine.edu> wrote: >On Mon, 24 Feb 2014, Vince Weaver wrote: > >> Just touching the mmap page with a write of a single byte (it doesn't > >> matter where) is enough to trigger the bug. > >OK, investigating this more. > >perf_fuzzer-2971 [000] 154.944114: page_fault_user: >address=0xf7729000 ip=0x41efab error_code=0x6 >perf_fuzzer-2971 [000] 154.944118: function: >ip=0xffffffff810d40e7 parent_ip=0xffffffff810d0840 >perf_fuzzer-2971 [000] 154.944119: function: >ip=0xffffffff812a91a5 parent_ip=0xffffffff81013ff5 >perf_fuzzer-2971 [000] 154.944120: function: >ip=0xffffffff8153837c parent_ip=0xffffffff81535432 >perf_fuzzer-2971 [000] 154.944121: page_fault_kernel: >address=0x22e0 ip=0xffffffff812a7d5c error_code=0x0 > >It looks like there are two page faults. The first is caused by the >user >code accessing the mmap'd page. It looks sort of normal and what you'd >expect if the perf_event mmap ring buffer is being accessed for the >first >time. > >What follows is a kernel page fault, and this is the one where for >whatever reason CR2 has obtained the value of the userspace RBP >register. > >Vince
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