Yes you are right. Each architecture implements clear_page() differently. Some may just use memset. Some may use architecture specific instructions to perform the zero-ing faster. I guess x86's fast_clear_page does that. -Fredrick On 01/18/2012 05:27 PM, 夏业添 wrote: > Thanks！ > > It seems that the function do_page_fault() will finally call > fast_clear_page() > <http://lxr.oss.org.cn/plain/source/arch/x86/lib/mmx_32.c#L125> or > slow_zero_page() > <http://lxr.oss.org.cn/plain/source/arch/x86/lib/mmx_32.c#L336> to zero > a new physical page for a process. So calling malloc() cannot get a page > used by another process which is dead already. > > The assemble language is difficult to me, so please tell me if I am wrong. > > 2012/1/18 Fredrick <fjohnber@xxxxxxxx <mailto:fjohnber@xxxxxxxx>> > > When you malloc a memory or mmap a MAP_ANON memory, it is virtually > allocated. When you read or write to it, the process takes a page > fault. The page fault handler zeroes those memory and hands it to > the process. So I think there is no leak. > > -Fredrick > > > On 01/11/2012 04:53 AM, 夏业添 wrote: > > Hi, > My tutor asked me to test whether one process leaves information in > memory after it is dead. I tried to search some article about > such thing > on the Internet but there seems to be no one discuss about it. > And after > that, I tried to write some program in the User Mode to test it, > using > fork() to create lots of processes and filling char 'a' into a > 102400 > bytes char array in each process. Then I used malloc() to get some > memory to seek char 'a' in a new one process or many new > processes, but > failed. All memory I malloced was full of zero. > As the man page of malloc said:"The memory is not initialized", I > believe that the memory which was got by malloc() could be used > by other > process, and therefor information leakage exists. But how can I > test it? > Or where can I get related information? > Thanks! > > > _________________________________________________ > Kernelnewbies mailing list > Kernelnewbies@kernelnewbies.__org > <mailto:Kernelnewbies@xxxxxxxxxxxxxxxxx> > http://lists.kernelnewbies.__org/mailman/listinfo/__kernelnewbies <http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies> > > > > > > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies@xxxxxxxxxxxxxxxxx > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
