From 1039bffd6ae9c75b42b7d148d6c1106134107b66 Mon Sep 17 00:00:00 2001 From: Xie Yuanbin Date: Tue, 28 Jul 2026 03:16:42 +0100 Subject: ARM: 9485/1: mm: acquire mmap write lock around show_pte() for user faults When CONFIG_DEBUG_USER=y, and cmdline "user_debug=31" is set, a user fault may trigger show_pte() without any lock. If another thread in the same process concurrently calls munmap(), the page table pages may be freed while show_pte() is still traversing them, causing a use-after-free in show_pte(). If CONFIG_ARM_LPAE=y, this may cause a kernel panic if the pages table of PMD are freed when show_pte() is running. Acquire mmap_write_lock() around show_pte() for user faults to fix the contention. For user faults, additionally restrict that show_pte() is called only when the addr is a user-space address (addr < TASK_SIZE). This is because the lock of tsk->mm only protects the virtual memory of user address space, furthermore, dumping the page tables of a kernel-space address for user faults is unnecessary and may have security implications. Keep everything unchanged for kernel faults, because the kernel is already in the "oops" state, acquiring a lock may risk a deadlock. Co-developed-by: Qi Xi Fixes: 6d021b724481 ("ARM: dump pgd, pmd and pte states on unhandled data abort faults") Link: https://lore.kernel.org/20260716014022.2823-1-xieyuanbin1@huawei.com Acked-by: Lorenzo Stoakes (ARM) Reviewed-by: Linus Walleij Signed-off-by: Qi Xi Signed-off-by: Xie Yuanbin Signed-off-by: Russell King --- net/openvswitch/flow_table.h | 115 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 115 insertions(+) create mode 100644 net/openvswitch/flow_table.h (limited to 'net/openvswitch/flow_table.h') diff --git a/net/openvswitch/flow_table.h b/net/openvswitch/flow_table.h new file mode 100644 index 000000000..f524dc3e4 --- /dev/null +++ b/net/openvswitch/flow_table.h @@ -0,0 +1,115 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Copyright (c) 2007-2013 Nicira, Inc. + */ + +#ifndef FLOW_TABLE_H +#define FLOW_TABLE_H 1 + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include +#include + +#include "flow.h" + +struct mask_cache_entry { + u32 skb_hash; + u32 mask_index; +}; + +struct mask_cache { + struct rcu_head rcu; + u32 cache_size; /* Must be ^2 value. */ + struct mask_cache_entry __percpu *mask_cache; +}; + +struct mask_count { + int index; + u64 counter; +}; + +struct mask_array_stats { + struct u64_stats_sync syncp; + u64 usage_cntrs[]; +}; + +struct mask_array { + struct rcu_head rcu; + int count, max; + struct mask_array_stats __percpu *masks_usage_stats; + u64 *masks_usage_zero_cntr; + struct sw_flow_mask __rcu *masks[] __counted_by(max); +}; + +struct table_instance { + struct hlist_head *buckets; + unsigned int n_buckets; + struct rcu_head rcu; + int node_ver; + u32 hash_seed; +}; + +struct flow_table { + struct table_instance __rcu *ti; + struct table_instance __rcu *ufid_ti; + struct mask_cache __rcu *mask_cache; + struct mask_array __rcu *mask_array; + unsigned long last_rehash; + unsigned int count; + unsigned int ufid_count; +}; + +extern struct kmem_cache *flow_stats_cache; + +int ovs_flow_init(void); +void ovs_flow_exit(void); + +struct sw_flow *ovs_flow_alloc(void); +void ovs_flow_free(struct sw_flow *, bool deferred); + +int ovs_flow_tbl_init(struct flow_table *); +int ovs_flow_tbl_count(const struct flow_table *table); +void ovs_flow_tbl_destroy(struct flow_table *table); +int ovs_flow_tbl_flush(struct flow_table *flow_table); + +int ovs_flow_tbl_insert(struct flow_table *table, struct sw_flow *flow, + const struct sw_flow_mask *mask); +void ovs_flow_tbl_remove(struct flow_table *table, struct sw_flow *flow); +int ovs_flow_tbl_num_masks(const struct flow_table *table); +u32 ovs_flow_tbl_masks_cache_size(const struct flow_table *table); +int ovs_flow_tbl_masks_cache_resize(struct flow_table *table, u32 size); +struct sw_flow *ovs_flow_tbl_dump_next(struct table_instance *table, + u32 *bucket, u32 *idx); +struct sw_flow *ovs_flow_tbl_lookup_stats(struct flow_table *, + const struct sw_flow_key *, + u32 skb_hash, + u32 *n_mask_hit, + u32 *n_cache_hit); +struct sw_flow *ovs_flow_tbl_lookup(struct flow_table *, + const struct sw_flow_key *); +struct sw_flow *ovs_flow_tbl_lookup_exact(struct flow_table *tbl, + const struct sw_flow_match *match); +struct sw_flow *ovs_flow_tbl_lookup_ufid(struct flow_table *, + const struct sw_flow_id *); + +bool ovs_flow_cmp(const struct sw_flow *, const struct sw_flow_match *); + +void ovs_flow_mask_key(struct sw_flow_key *dst, const struct sw_flow_key *src, + bool full, const struct sw_flow_mask *mask); + +void ovs_flow_masks_rebalance(struct flow_table *table); +void table_instance_flow_flush(struct flow_table *table, + struct table_instance *ti, + struct table_instance *ufid_ti); + +#endif /* flow_table.h */ -- cgit v1.3.1