Re: [PATCH v9 08/69] mm: start tracking VMAs with maple tree

Qian Cai
2022-05-12T17:01:31Z

On Wed, May 04, 2022 at 01:07:52AM +0000, Liam Howlett wrote:
> From: "Liam R. Howlett" <Liam.Howlett@Oracle.com>
>
> Start tracking the VMAs with the new maple tree structure in parallel with
> the rb_tree. Add debug and trace events for maple tree operations and
> duplicate the rb_tree that is created on forks into the maple tree.
>
> The maple tree is added to the mm_struct including the mm_init struct,
> added support in required mm/mmap functions, added tracking in kernel/fork
> for process forking, and used to find the unmapped_area and checked
> against what the rbtree finds.
>
> This also moves the mmap_lock() in exit_mmap() since the oom reaper call
> does walk the VMAs. Otherwise lockdep will be unhappy if oom happens.
>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
...
> @@ -2479,9 +2693,14 @@ int expand_downwards(struct vm_area_struct *vma,
> return -ENOMEM;
> }
>
> + if (mas_preallocate(&mas, vma, GFP_KERNEL))

We have thousands of leaks reports here from kmemleak while running some
syscall fuzzers on today's linux-next tree.

unreferenced object 0xffff0803c0063d00 (size 256):
comm "trinity-c25", pid 177739, jiffies 4297781293 (age 354.988s)
hex dump (first 32 bytes):
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
backtrace:
slab_post_alloc_hook
kmem_cache_alloc_bulk
mas_alloc_nodes
mas_preallocate
mas_preallocate at lib/maple_tree.c:5579
expand_downwards
expand_downwards at mm/mmap.c:2094
expand_stack
do_page_fault
do_translation_fault
do_mem_abort
el1_abort
el1h_64_sync_handler
el1h_64_sync
handle_futex_death
exit_robust_list
futex_exit_release
exit_mm_release

> + return -ENOMEM;
> +
> /* We must make sure the anon_vma is allocated. */
> - if (unlikely(anon_vma_prepare(vma)))
> + if (unlikely(anon_vma_prepare(vma))) {
> + mas_destroy(&mas);
> return -ENOMEM;
> + }
>
> /*
> * vma->vm_start/vm_end cannot change under us because the caller