From 14611508cb5bf031f85bae58704c9218681d8e07 Mon Sep 17 00:00:00 2001 From: Jann Horn Date: Wed, 16 Oct 2024 17:07:53 +0200 Subject: [PATCH] mm: mark mas allocation in vms_abort_munmap_vmas as __GFP_NOFAIL vms_abort_munmap_vmas() is a recovery path where, on entry, some VMAs have already been torn down halfway (in a way we can't undo) but are still present in the maple tree. At this point, we *must* remove the VMAs from the VMA tree, otherwise we get UAF. Because removing VMA tree nodes can require memory allocation, the existing code has an error path which tries to handle this by reattaching the VMAs; but that can't be done safely. A nicer way to fix it would probably be to preallocate enough maple tree nodes for the removal before the point of no return, or something like that; but for now, fix it the easy and kinda ugly way, by marking this allocation __GFP_NOFAIL. Link: https://lkml.kernel.org/r/20241016-fix-munmap-abort-v1-1-601c94b2240d@google.com Fixes: 4f87153e82c4 ("mm: change failure of MAP_FIXED to restoring the gap on failure") Signed-off-by: Jann Horn Reviewed-by: Liam R. Howlett Acked-by: Vlastimil Babka Reviewed-by: Lorenzo Stoakes Signed-off-by: Andrew Morton --- mm/vma.h | 12 +++--------- 1 file changed, 3 insertions(+), 9 deletions(-) diff --git a/mm/vma.h b/mm/vma.h index 819f994cf727..ebd78f1577f3 100644 --- a/mm/vma.h +++ b/mm/vma.h @@ -241,15 +241,9 @@ static inline void vms_abort_munmap_vmas(struct vma_munmap_struct *vms, * failure method of leaving a gap where the MAP_FIXED mapping failed. */ mas_set_range(mas, vms->start, vms->end - 1); - if (unlikely(mas_store_gfp(mas, NULL, GFP_KERNEL))) { - pr_warn_once("%s: (%d) Unable to abort munmap() operation\n", - current->comm, current->pid); - /* Leaving vmas detached and in-tree may hamper recovery */ - reattach_vmas(mas_detach); - } else { - /* Clean up the insertion of the unfortunate gap */ - vms_complete_munmap_vmas(vms, mas_detach); - } + mas_store_gfp(mas, NULL, GFP_KERNEL|__GFP_NOFAIL); + /* Clean up the insertion of the unfortunate gap */ + vms_complete_munmap_vmas(vms, mas_detach); } int