On 06/14/24 at 09:05am, zhaoyang.huang wrote:

From: Zhaoyang Huang zhaoyang.huang@unisoc.com

The function xa_for_each() in _vm_unmap_aliases() loops through all vbs. However, since commit 062eacf57ad9 ("mm: vmalloc: remove a global vmap_blocks xarray") the vb from xarray may not be on the corresponding CPU vmap_block_queue. Consequently, purge_fragmented_block() might use the wrong vbq->lock to protect the free list, leading to vbq->free breakage.

Incorrect lock protection can exhaust all vmalloc space as follows: CPU0 CPU1 +--------------------------------------------+ | +--------------------+ +-----+ | +--> | |---->| |------+ | CPU1:vbq free_list | | vb1 | +--- | |<----| |<-----+ | +--------------------+ +-----+ | +--------------------------------------------+

_vm_unmap_aliases() vb_alloc() new_vmap_block() xa_for_each(&vbq->vmap_blocks, idx, vb) --> vb in CPU1:vbq->freelist

purge_fragmented_block(vb) spin_lock(&vbq->lock) spin_lock(&vbq->lock) --> use CPU0:vbq->lock --> use CPU1:vbq->lock

list_del_rcu(&vb->free_list) list_add_tail_rcu(&vb->free_list, &vbq->free) __list_del(vb->prev, vb->next) next->prev = prev +--------------------+ | | | CPU1:vbq free_list | +---| |<--+ | +--------------------+ | +----------------------------+ __list_add(new, head->prev, head) +--------------------------------------------+ | +--------------------+ +-----+ | +--> | |---->| |------+ | CPU1:vbq free_list | | vb2 | +--- | |<----| |<-----+ | +--------------------+ +-----+ | +--------------------------------------------+

    prev->next = next

+--------------------------------------------+ |----------------------------+ | | +--------------------+ | +-----+ | +--> | |--+ | |------+ | CPU1:vbq free_list | | vb2 | +--- | |<----| |<-----+ | +--------------------+ +-----+ | +--------------------------------------------+ Here’s a list breakdown. All vbs, which were to be added to ‘prev’, cannot be used by list_for_each_entry_rcu(vb, &vbq->free, free_list) in vb_alloc(). Thus, vmalloc space is exhausted.

This issue affects both erofs and f2fs, the stacktrace is as follows: erofs: [<ffffffd4ffb93ad4>] __switch_to+0x174 [<ffffffd4ffb942f0>] __schedule+0x624 [<ffffffd4ffb946f4>] schedule+0x7c [<ffffffd4ffb947cc>] schedule_preempt_disabled+0x24 [<ffffffd4ffb962ec>] __mutex_lock+0x374 [<ffffffd4ffb95998>] __mutex_lock_slowpath+0x14 [<ffffffd4ffb95954>] mutex_lock+0x24 [<ffffffd4fef2900c>] reclaim_and_purge_vmap_areas+0x44 [<ffffffd4fef25908>] alloc_vmap_area+0x2e0 [<ffffffd4fef24ea0>] vm_map_ram+0x1b0 [<ffffffd4ff1b46f4>] z_erofs_lz4_decompress+0x278 [<ffffffd4ff1b8ac4>] z_erofs_decompress_queue+0x650 [<ffffffd4ff1b8328>] z_erofs_runqueue+0x7f4 [<ffffffd4ff1b66a8>] z_erofs_read_folio+0x104 [<ffffffd4feeb6fec>] filemap_read_folio+0x6c [<ffffffd4feeb68c4>] filemap_fault+0x300 [<ffffffd4fef0ecac>] __do_fault+0xc8 [<ffffffd4fef0c908>] handle_mm_fault+0xb38 [<ffffffd4ffb9f008>] do_page_fault+0x288 [<ffffffd4ffb9ed64>] do_translation_fault[jt]+0x40 [<ffffffd4fec39c78>] do_mem_abort+0x58 [<ffffffd4ffb8c3e4>] el0_ia+0x70 [<ffffffd4ffb8c260>] el0t_64_sync_handler[jt]+0xb0 [<ffffffd4fec11588>] ret_to_user[jt]+0x0

f2fs: [<ffffffd4ffb93ad4>] __switch_to+0x174 [<ffffffd4ffb942f0>] __schedule+0x624 [<ffffffd4ffb946f4>] schedule+0x7c [<ffffffd4ffb947cc>] schedule_preempt_disabled+0x24 [<ffffffd4ffb962ec>] __mutex_lock+0x374 [<ffffffd4ffb95998>] __mutex_lock_slowpath+0x14 [<ffffffd4ffb95954>] mutex_lock+0x24 [<ffffffd4fef2900c>] reclaim_and_purge_vmap_areas+0x44 [<ffffffd4fef25908>] alloc_vmap_area+0x2e0 [<ffffffd4fef24ea0>] vm_map_ram+0x1b0 [<ffffffd4ff1a3b60>] f2fs_prepare_decomp_mem+0x144 [<ffffffd4ff1a6c24>] f2fs_alloc_dic+0x264 [<ffffffd4ff175468>] f2fs_read_multi_pages+0x428 [<ffffffd4ff17b46c>] f2fs_mpage_readpages+0x314 [<ffffffd4ff1785c4>] f2fs_readahead+0x50 [<ffffffd4feec3384>] read_pages+0x80 [<ffffffd4feec32c0>] page_cache_ra_unbounded+0x1a0 [<ffffffd4feec39e8>] page_cache_ra_order+0x274 [<ffffffd4feeb6cec>] do_sync_mmap_readahead+0x11c [<ffffffd4feeb6764>] filemap_fault+0x1a0 [<ffffffd4ff1423bc>] f2fs_filemap_fault+0x28 [<ffffffd4fef0ecac>] __do_fault+0xc8 [<ffffffd4fef0c908>] handle_mm_fault+0xb38 [<ffffffd4ffb9f008>] do_page_fault+0x288 [<ffffffd4ffb9ed64>] do_translation_fault[jt]+0x40 [<ffffffd4fec39c78>] do_mem_abort+0x58 [<ffffffd4ffb8c3e4>] el0_ia+0x70 [<ffffffd4ffb8c260>] el0t_64_sync_handler[jt]+0xb0 [<ffffffd4fec11588>] ret_to_user[jt]+0x0

To fix this, replace xa_for_each() with list_for_each_entry_rcu() which reverts commit fc1e0d980037 ("mm/vmalloc: prevent stale TLBs in fully utilized blocks")

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This paragraph need be updated?

Fixes: fc1e0d980037 ("mm/vmalloc: prevent stale TLBs in fully utilized blocks")

Cc: stable@vger.kernel.org Suggested-by: Hailong.Liu hailong.liu@oppo.com Signed-off-by: Zhaoyang Huang zhaoyang.huang@unisoc.com

---

v2: introduce cpu in vmap_block to record the right CPU number v3: use get_cpu/put_cpu to prevent schedule between core v4: replace get_cpu/put_cpu by another API to avoid disabling preemption v5: update the commit message by Hailong.Liu

---

---

mm/vmalloc.c | 21 +++++++++++++++------ 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 22aa63f4ef63..89eb034f4ac6 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2458,6 +2458,7 @@ struct vmap_block { struct list_head free_list; struct rcu_head rcu_head; struct list_head purge;

• unsigned int cpu;

}; /* Queue of free and dirty vmap blocks, for allocation and flushing purposes */ @@ -2585,8 +2586,15 @@ static void *new_vmap_block(unsigned int order, gfp_t gfp_mask) free_vmap_area(va); return ERR_PTR(err); }

• vbq = raw_cpu_ptr(&vmap_block_queue);

• /*

• * list_add_tail_rcu could happened in another core
  

• * rather than vb->cpu due to task migration, which
  

• * is safe as list_add_tail_rcu will ensure the list's
  

• * integrity together with list_for_each_rcu from read
  

• * side.
  

• */
  

Do we still need above code comment? No lock gurantees vb->cpu is from the cpu where vb_alloc() is called, it could be from the cpu where migration moved to. We don't care about it as long as the vbq->lock correctly protect the vb on its vbq->free?

• vb->cpu = raw_smp_processor_id();
• vbq = per_cpu_ptr(&vmap_block_queue, vb->cpu); spin_lock(&vbq->lock); list_add_tail_rcu(&vb->free_list, &vbq->free); spin_unlock(&vbq->lock);

@@ -2614,9 +2622,10 @@ static void free_vmap_block(struct vmap_block *vb) } static bool purge_fragmented_block(struct vmap_block *vb,

• struct vmap_block_queue *vbq, struct list_head *purge_list,
  

• bool force_purge)
  

• struct list_head *purge_list, bool force_purge)
  

{

• struct vmap_block_queue *vbq = &per_cpu(vmap_block_queue, vb->cpu);
• if (vb->free + vb->dirty != VMAP_BBMAP_BITS || vb->dirty == VMAP_BBMAP_BITS) return false;

@@ -2664,7 +2673,7 @@ static void purge_fragmented_blocks(int cpu) continue; spin_lock(&vb->lock);

• purge_fragmented_block(vb, vbq, &purge, true);
  

• purge_fragmented_block(vb, &purge, true);
  

  spin_unlock(&vb->lock); } rcu_read_unlock();

@@ -2801,7 +2810,7 @@ static void _vm_unmap_aliases(unsigned long start, unsigned long end, int flush) * not purgeable, check whether there is dirty * space to be flushed. */

• 	if (!purge_fragmented_block(vb, vbq, &purge_list, false) &&
  

• 	if (!purge_fragmented_block(vb, &purge_list, false) &&
      vb->dirty_max && vb->dirty != VMAP_BBMAP_BITS) {
  	unsigned long va_start = vb->va->va_start;
  	unsigned long s, e;
  

-- 2.25.1