Been a few more days. Not sure how often I should be pinging. If this is too much to ping every few days let me know.
On Fri, May 15, 2020 at 7:36 AM Jonathan Marler <johnnymar...@gmail.com> wrote: > Been a couple weeks, checking to see if anyone has looked at this. > > On Sat, May 2, 2020 at 5:43 PM Jonathan Marler <johnnymar...@gmail.com> > wrote: > >> FYI, I applied this patch to the qemu build that zig uses to run >> non-native tests ( >> https://github.com/ziglang/qemu-static/blob/master/patch/mremap-underflow.diff >> ) >> >> After applying it, my new code that calls mremap now passes, >> whereas before the fix I was getting a segfault. >> >> On Sat, May 2, 2020 at 10:12 AM Jonathan Marler <johnnymar...@gmail.com> >> wrote: >> >>> Fixes: https://bugs.launchpad.net/bugs/1876373 >>> >>> This code path in mmap occurs when a page size is decreased with >>> mremap. When a section of pages is shrunk, qemu calls mmap_reserve on the >>> pages that were released. However, it has the diff operation reversed, >>> subtracting the larger old_size from the smaller new_size. Instead, it >>> should be subtracting the smaller new_size from the larger old_size. You >>> can also see in the previous line of the change that this mmap_reserve call >>> only occurs when old_size > new_size. >>> >>> Signed-off-by: Jonathan Marler <johnnymar...@gmail.com> >>> --- >>> linux-user/mmap.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/linux-user/mmap.c b/linux-user/mmap.c >>> index e378033797..caab62909e 100644 >>> --- a/linux-user/mmap.c >>> +++ b/linux-user/mmap.c >>> @@ -708,7 +708,7 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong >>> old_size, >>> if (prot == 0) { >>> host_addr = mremap(g2h(old_addr), old_size, new_size, >>> flags); >>> if (host_addr != MAP_FAILED && reserved_va && old_size > >>> new_size) { >>> - mmap_reserve(old_addr + old_size, new_size - old_size); >>> + mmap_reserve(old_addr + old_size, old_size - new_size); >>> } >>> } else { >>> errno = ENOMEM; >>> -- >>> 2.23.1 >>> >>>
