Messages in this thread | | | Subject | Re: [PATCH] mm: optionally disable brk() | From | Topi Miettinen <> | Date | Mon, 5 Oct 2020 12:47:03 +0300 |
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On 5.10.2020 12.13, David Hildenbrand wrote: > On 05.10.20 08:12, Michal Hocko wrote: >> On Sat 03-10-20 00:44:09, Topi Miettinen wrote: >>> On 2.10.2020 20.52, David Hildenbrand wrote: >>>> On 02.10.20 19:19, Topi Miettinen wrote: >>>>> The brk() system call allows to change data segment size (heap). This >>>>> is mainly used by glibc for memory allocation, but it can use mmap() >>>>> and that results in more randomized memory mappings since the heap is >>>>> always located at fixed offset to program while mmap()ed memory is >>>>> randomized. >>>> >>>> Want to take more Unix out of Linux? >>>> >>>> Honestly, why care about disabling? User space can happily use mmap() if >>>> it prefers. >>> >>> brk() interface doesn't seem to be used much and glibc is happy to switch to >>> mmap() if brk() fails, so why not allow disabling it optionally? If you >>> don't care to disable, don't do it and this is even the default. >> >> I do not think we want to have config per syscall, do we? > > I do wonder if grouping would be a better option then (finding a proper > level of abstraction ...).
If hardening and compatibility are seen as tradeoffs, perhaps there could be a top level config choice (CONFIG_HARDENING_TRADEOFF) for this. It would have options - "compatibility" (default) to gear questions for maximum compatibility, deselecting any hardening options which reduce compatibility - "hardening" to gear questions for maximum hardening, deselecting any compatibility options which reduce hardening - "none/manual": ask all questions like before
-Topi
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