Messages in this thread | | | Date | Sun, 18 Dec 2011 17:48:32 -0500 | From | KOSAKI Motohiro <> | Subject | Re: [PATCH][RESEND] mm: Fix off-by-one bug in print_nodes_state |
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(12/18/11 5:44 PM), David Rientjes wrote: > On Sun, 18 Dec 2011, Ryota Ozaki wrote: > >> /sys/devices/system/node/{online,possible} involve a garbage byte >> because print_nodes_state returns content size + 1. To fix the bug, >> the patch changes the use of cpuset_sprintf_cpulist to follow the >> use at other places, which is clearer and safer. >> > > It's not a garbage byte, sysdev files use a buffer created with > get_zeroed_page(), so extra byte is guaranteed to be zero since > nodelist_scnprintf() won't write to it. So the issue here is that > print_nodes_state() returns a size that is off by one according to > ISO C99 although it won't cause a problem in practice. > >> This bug was introduced since v2.6.24. >> > > It's not a bug, the result of a 4-node system would be "0-3\n\0" and > returns 5 correctly. You can verify this very simply with strace.
Usually, /sys files don't output trailing '¥0'. And, '¥0' is not regular io friendly. So I can imagine some careless programmer think it is garbage. Is there any benefit to show trailing '¥0'?
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