On Thu, Mar 13, 2025 at 10:23 PM Collin Funk <collin.fu...@gmail.com> wrote: > > On Haiku, test-vma-prot fails with the following: > > ../../gltests/test-vma-prot.c:68: assertion 'prot == (VMA_PROT_READ | > VMA_PROT_WRITE)' failed > Abort > FAIL test-vma-prot (exit status: 149) > > At this point, the following instead is true: > > prot == (VMA_PROT_READ | VMA_PROT_WRITE | VMA_PROT_EXECUTE) > > I guess when the original code here was written: > > if (info.protection & B_READ_AREA) > flags |= VMA_PROT_READ | VMA_PROT_EXECUTE; > > the assumption was that readable memory was also executable?
For modern Linux, I believe the preferred state is written as W^X, meaning the page is either WRITE or EXEC, but not both. It is a defense for attacks like buffer overflows and heap spraying. Linux used to set READ, WRITE and/or EXEC by default on memory, but it changed to W^X back around 2010 or 2012 or so. I think setting both READ and EXEC by default is probably an architectural bug on Haiku. > The only documentation I could find for this BeOS/Haiku API only > mentions B_READ_AREA and B_WRITE_AREA [1]. > > But I see that when mmap was added in 2008 to Haiku it also sets > B_EXECUTE_AREA [2]. Therefore, I applied the attached patch to vma-iter > that fixes the test. > > [1] https://www.haiku-os.org/legacy-docs/bebook/TheKernelKit_Areas.html > [2] > https://github.com/haiku/haiku/blame/b989960b81e5826d54acad82a2c4a3e685984f8a/src/system/libroot/posix/sys/mman.cpp#L132 Jeff
