Date: Thu, 11 Aug 2011 10:54:58 -0400 From: Rich Felker <dalias@...ifal.cx> To: musl@...ts.openwall.com Subject: Re: malloc and linux memory layout On Thu, Aug 11, 2011 at 11:43:05AM +0400, Vasiliy Kulikov wrote: > > The mmap zone (where mmaps are put by > > default) starts just below the stack limit and continues downward as > > more mappings are made. > > Not only this zone. mmap() can return address before main program text if > there is enough space there. Interesting. > Other minor (Linux-specific) things: > > Low unmappable pages region might be absent if the task has CAP_SYS_RAWIO > capability. But pages before mmap_min_addr will be mmap'ed only by > explicit mmap(addr, ..., MAP_FIXED, ...), no libs will be there. This is mostly irrelevant since it requires root or equivalent. (CAP_SYS_RAWIO might as well be root since it lets you exploit kernelspace null pointer dereference bugs to get root). > "Reserved for kernelspace use" region might be absent too for 32-bit > tasks running on 286-64 system. Nice. Rich
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