The patch titled Subject: maple_tree: fix mas_skip_node() end slot detection has been added to the -mm mm-hotfixes-unstable branch. Its filename is maple_tree-fix-mas_skip_node-end-slot-detection.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: "Liam R. Howlett" Liam.Howlett@oracle.com Subject: maple_tree: fix mas_skip_node() end slot detection Date: Thu, 2 Mar 2023 21:15:39 -0500

mas_skip_node() is used to move the maple state to the node with a higher limit. It does this by walking up the tree and increasing the slot count. Since slot count may not be able to be increased, it may need to walk up multiple times to find room to walk right to a higher limit node. The limit of slots that was being used was the node limit and not the last location of data in the node. This would cause the maple state to be shifted outside actual data and enter an error state, thus returning -EBUSY.

The result of the incorrect error state means that mas_awalk() would return an error instead of finding the allocation space.

The fix is to use mas_data_end() in mas_skip_node() to detect the nodes data end point and continue walking the tree up until it is safe to move to a node with a higher limit.

mas_skip_node() may also be passed a maple state in an error state from mas_anode_descend() when no allocations are available. Return on such an error state immediately.

Link: https://lkml.kernel.org/r/20230303021540.1056603-1-Liam.Howlett@oracle.com Fixes: 54a611b60590 ("Maple Tree: add new data structure") Signed-off-by: Liam R. Howlett Liam.Howlett@oracle.com Reported-by: Snild Dolkow snild@sony.com Link: https://lore.kernel.org/linux-mm/cb8dc31a-fef2-1d09-f133-e9f7b9f9e77a@sony.c... Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

--- a/lib/maple_tree.c~maple_tree-fix-mas_skip_node-end-slot-detection +++ a/lib/maple_tree.c @@ -5099,34 +5099,29 @@ static inline bool mas_rewind_node(struc */ static inline bool mas_skip_node(struct ma_state *mas) { - unsigned char slot, slot_count; unsigned long *pivots; enum maple_type mt;

- mt = mte_node_type(mas->node); - slot_count = mt_slots[mt] - 1; + if (mas_is_err(mas)) + return false; + do { if (mte_is_root(mas->node)) { - slot = mas->offset; - if (slot > slot_count) { + if (mas->offset >= mas_data_end(mas)) { mas_set_err(mas, -EBUSY); return false; } } else { mas_ascend(mas); - slot = mas->offset; - mt = mte_node_type(mas->node); - slot_count = mt_slots[mt] - 1; } - } while (slot > slot_count); + } while (mas->offset >= mas_data_end(mas));

- mas->offset = ++slot; + mt = mte_node_type(mas->node); pivots = ma_pivots(mas_mn(mas), mt); - if (slot > 0) - mas->min = pivots[slot - 1] + 1; - - if (slot <= slot_count) - mas->max = pivots[slot]; + mas->min = pivots[mas->offset] + 1; + mas->offset++; + if (mas->offset < mt_slots[mt]) + mas->max = pivots[mas->offset];

return true; } _

Patches currently in -mm which might be from Liam.Howlett@oracle.com are

mm-mprotect-fix-successful-vma_merge-of-next-in-do_mprotect_pkey.patch maple_tree-fix-mas_skip_node-end-slot-detection.patch test_maple_tree-add-more-testing-for-mas_empty_area.patch maple_tree-be-more-cautious-about-dead-nodes.patch maple_tree-detect-dead-nodes-in-mas_start.patch maple_tree-fix-freeing-of-nodes-in-rcu-mode.patch maple_tree-remove-extra-smp_wmb-from-mas_dead_leaves.patch maple_tree-fix-write-memory-barrier-of-nodes-once-dead-for-rcu-mode.patch maple_tree-add-smp_rmb-to-dead-node-detection.patch maple_tree-add-rcu-lock-checking-to-rcu-callback-functions.patch mm-enable-maple-tree-rcu-mode-by-default.patch