On Tue, Oct 22, 2024 at 09:40:51PM +0100, Lorenzo Stoakes wrote: > The mmap_region() function is somewhat terrifying, with spaghetti-like > control flow and numerous means by which issues can arise and incomplete > state, memory leaks and other unpleasantness can occur. > > A large amount of the complexity arises from trying to handle errors late > in the process of mapping a VMA, which forms the basis of recently observed > issues with resource leaks and observable inconsistent state. > > This series goes to great lengths to simplify how mmap_region() works and > to avoid unwinding errors late on in the process of setting up the VMA for > the new mapping, and equally avoids such operations occurring while the VMA > is in an inconsistent state. > > The first four patches are intended for backporting to correct the > possibility of people encountering corrupted state while invoking mmap() > which is otherwise at risk of happening. > > After this we go further, refactoring the code, placing it in mm/vma.c in > order to make it eventually userland testable, and significantly > simplifying the logic to avoid this issue arising in future. > > Lorenzo Stoakes (8): > mm: avoid unsafe VMA hook invocation when error arises on mmap hook > mm: unconditionally close VMAs on error > mm: refactor map_deny_write_exec() > mm: resolve faulty mmap_region() error path behaviour > tools: testing: add additional vma_internal.h stubs > mm: insolate mmap internal logic to mm/vma.c > mm: refactor __mmap_region() > mm: do not attempt second merge for file-backed VMAs > > include/linux/mman.h | 21 +- > mm/internal.h | 44 ++++ > mm/mmap.c | 262 ++------------------ > mm/mprotect.c | 2 +- > mm/nommu.c | 7 +- > mm/vma.c | 403 ++++++++++++++++++++++++++++++- > mm/vma.h | 101 +------- > mm/vma_internal.h | 5 + > tools/testing/vma/vma_internal.h | 106 +++++++- > 9 files changed, 591 insertions(+), 360 deletions(-) > > -- > 2.47.0 To clarify - this applies against Andrew's tree [0] in the mm-hotfixes-unstable branch in order to be applicable against outstanding hotfix patches for 6.12. [0]:https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git/
