Messages in this thread | | | Date | Sat, 30 May 2009 17:06:39 +0800 | From | Li Zefan <> | Subject | Re: [PATCH 2/2] tracing/filters: use strcmp() instead of strncmp() |
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Frédéric Weisbecker wrote: > 2009/5/29 Li Zefan <lizf@cn.fujitsu.com>: >> Trace filter is not working normally: >> >> # echo 'name == et' > tracing/events/irq/irq_handler_entry/filter >> # echo 1 > tracing/events/irq/irq_handler_entry/enable >> # cat trace_pipe >> <idle>-0 [001] 1363.423175: irq_handler_entry: irq=18 handler=eth0 >> <idle>-0 [001] 1363.934528: irq_handler_entry: irq=18 handler=eth0 >> ... >> >> It's because we pass to trace_define_field() the information of >> __str_loc_##item, but not the actual string, so pred->str_len == field->size >> == sizeof(unsigned short), thus it always compare at most 2 bytes when >> filtering on __string() field. > > > Weird, I was about sure I set the size of each string() to FILTER_MAX_STRING (or > something like that). > > Anyway this patch looks good but it does more than just fixing the > issue, it removes > the string len boundary security we had with strncmp() for every > string (static and > dynamic size). > > The potential side effect that comes along this patch would disappear if > you just turn strncmp into strcmp only in filter_pred_strloc(). > > If you do that also for fixed size strings, then it should be done in > a second patch, > although I guess turning anything here into strcmp is fine because the > strings given > by the user are always limited in their size. But we never know... >
I don't think there's any security issue. It's irrelevant how big the user-input strings are. The point is those strings are guaranteed to be NULL-terminated. Am I missing something?
And I don't think it's necessary to make 2 patches that each patch converts one strncmp to strcmp. But maybe it's better to improve this changelog?
> > Thanks, > Frederic. > > >> Since __string() is dynamic size, we are not able to set field->size to >> string length. Thus this patch uses strcmp() instead of strncmp(). >> >> [ Impact: make filter facility working normally for __string() field ] >> >> Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> >> --- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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