The patch titled Subject: mm: fix incorrect vbq reference in purge_fragmented_block has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-fix-incorrect-vbq-reference-in-purge_fragmented_block.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Zhaoyang Huang zhaoyang.huang@unisoc.com Subject: mm: fix incorrect vbq reference in purge_fragmented_block Date: Fri, 7 Jun 2024 10:31:16 +0800

vmalloc area runs out in our ARM64 system during an erofs test as vm_map_ram failed[1]. By following the debug log, we find that vm_map_ram()->vb_alloc() will allocate new vb->va which corresponding to 4MB vmalloc area as list_for_each_entry_rcu returns immediately when vbq->free->next points to vbq->free. That is to say, 65536 times of page fault after the list's broken will run out of the whole vmalloc area. This should be introduced by one vbq->free->next point to vbq->free which makes list_for_each_entry_rcu can not iterate the list and find the BUG.

[1] PID: 1 TASK: ffffff80802b4e00 CPU: 6 COMMAND: "init" #0 [ffffffc08006afe0] __switch_to at ffffffc08111d5cc #1 [ffffffc08006b040] __schedule at ffffffc08111dde0 #2 [ffffffc08006b0a0] schedule at ffffffc08111e294 #3 [ffffffc08006b0d0] schedule_preempt_disabled at ffffffc08111e3f0 #4 [ffffffc08006b140] __mutex_lock at ffffffc08112068c #5 [ffffffc08006b180] __mutex_lock_slowpath at ffffffc08111f8f8 #6 [ffffffc08006b1a0] mutex_lock at ffffffc08111f834 #7 [ffffffc08006b1d0] reclaim_and_purge_vmap_areas at ffffffc0803ebc3c #8 [ffffffc08006b290] alloc_vmap_area at ffffffc0803e83fc #9 [ffffffc08006b300] vm_map_ram at ffffffc0803e78c0

For detailed descri[ption of the broken list, please see https://lore.kernel.org/all/20240531024820.5507-1-hailong.liu@oppo.com/

Link: https://lkml.kernel.org/r/20240607023116.1720640-1-zhaoyang.huang@unisoc.com Fixes: fc1e0d980037 ("mm/vmalloc: prevent stale TLBs in fully utilized blocks") Signed-off-by: Zhaoyang Huang zhaoyang.huang@unisoc.com Suggested-by: Hailong.Liu hailong.liu@oppo.com Reviewed-by: Uladzislau Rezki (Sony) urezki@gmail.com Cc: Baoquan He bhe@redhat.com Cc: Christoph Hellwig hch@infradead.org Cc: Lorenzo Stoakes lstoakes@gmail.com Cc: Thomas Gleixner tglx@linutronix.de Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

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

--- a/mm/vmalloc.c~mm-fix-incorrect-vbq-reference-in-purge_fragmented_block +++ a/mm/vmalloc.c @@ -2498,6 +2498,7 @@ 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 */ @@ -2625,8 +2626,15 @@ static void *new_vmap_block(unsigned int 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. + */ + 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); @@ -2654,9 +2662,10 @@ static void free_vmap_block(struct vmap_ }

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; @@ -2704,7 +2713,7 @@ static void purge_fragmented_blocks(int 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(); @@ -2841,7 +2850,7 @@ static void _vm_unmap_aliases(unsigned l * 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; _

Patches currently in -mm which might be from zhaoyang.huang@unisoc.com are

mm-fix-incorrect-vbq-reference-in-purge_fragmented_block.patch mm-optimization-on-page-allocation-when-cma-enabled.patch