On Mon, Dec 5, 2022 at 3:50 PM Liam Howlett <liam.howlett@xxxxxxxxxx> wrote: > * Jann Horn <jannh@xxxxxxxxxx> [221202 13:54]: > > As of commit ca57f02295f, brk() can expand ordinary file mappings (but > > not file mappings with weird flags), and I think it does it with > > insufficient locks. I think brk() probably needs some extra checks to > > make sure it's operating on a brk-like VMA (which means it should at > > least be anonymous, and perhaps pass the full can_vma_merge_after() > > check so that we're not creating unnecessary special cases?). > > > Thanks. This is probably caused by commit 2e7ce7d354f2: "mm/mmap: > change do_brk_flags() to expand existing VMA and add do_brk_munmap()" Yeah. > Specifically the checks around expanding the VMA. > > > user@vm:~/brk_stretch$ cat brk_file.c > > Thanks for the testcase. I have a fix that I'm testing, but it's worth > noting that the brk call will succeed - except a new VMA will be > created. Is this what you expect? Yes, that's what I would expect.
