[PATCH OLK-5.10 0/2] Fix UAF problem of hpool

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[PATCH OLK-5.10 v2 0/2] Fix UAF...

[PATCH openEuler-22.03-LTS-SP1]...

Liu Shixin

14 Jun 2024 14 Jun '24

4:02 p.m.

Add rcu lock protection to avoid get refcount of hpool after it has been freed.

Liu Shixin (2): mm/dynamic_hugetlb: simplify the refcount code mm/dynamic_hugetlb: use rcu lock to protect hpool

mm/dynamic_hugetlb.c | 128 +++++++++++++++++++++++++++---------------- 1 file changed, 82 insertions(+), 46 deletions(-)

-- 2.25.1

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14 Jun 14 Jun

3 p.m.

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Liu Shixin

4:02 p.m.

New subject: [PATCH OLK-5.10 1/2] mm/dynamic_hugetlb: simplify the refcount code

Offering: HULK hulk inclusion category: cleanup bugzilla: https://gitee.com/openeuler/kernel/issues/IA53JK

--------------------------------

There are three ways to obtain hpool, from memcg, hugetlbfs, pagelist. After we obtain a hpool, we try to increase its refcount at first. Define three get_hpool_from_*() helper to simplify the code. These function will increase the refcount of hpool or return NULL.

Signed-off-by: Liu Shixin liushixin2@huawei.com --- mm/dynamic_hugetlb.c | 121 +++++++++++++++++++++++++++---------------- 1 file changed, 75 insertions(+), 46 deletions(-)

diff --git a/mm/dynamic_hugetlb.c b/mm/dynamic_hugetlb.c index 72061fd0395e..f6c4c01eae8e 100644 --- a/mm/dynamic_hugetlb.c +++ b/mm/dynamic_hugetlb.c @@ -442,14 +442,14 @@ static int hugetlb_pool_merge_all_pages(struct dhugetlb_pool *hpool)

static bool get_hpool_unless_zero(struct dhugetlb_pool *hpool) { - if (!dhugetlb_enabled || !hpool) + if (!hpool) return false; return atomic_inc_not_zero(&hpool->refcnt); }

static void put_hpool(struct dhugetlb_pool *hpool) { - if (!dhugetlb_enabled || !hpool) + if (!hpool) return; if (atomic_dec_and_test(&hpool->refcnt)) { css_put(&hpool->attach_memcg->css); @@ -465,6 +465,31 @@ struct dhugetlb_pagelist { static struct dhugetlb_pagelist *dhugetlb_pagelist_t; static DEFINE_RWLOCK(dhugetlb_pagelist_rwlock);

+static struct dhugetlb_pool *get_hpool_from_memcg(struct mem_cgroup *memcg) +{ + struct dhugetlb_pool *hpool; + + hpool = memcg->hpool; + if (!get_hpool_unless_zero(hpool)) + hpool = NULL; + + return hpool; +} + +static struct dhugetlb_pool *get_hpool_from_task(struct task_struct *tsk) +{ + struct mem_cgroup *memcg; + + rcu_read_lock(); + memcg = mem_cgroup_from_task(tsk); + rcu_read_unlock(); + + if (!memcg) + return NULL; + + return get_hpool_from_memcg(memcg); +} + static int set_hpool_in_dhugetlb_pagelist(unsigned long idx, struct dhugetlb_pool *hpool) { /* @@ -504,7 +529,7 @@ static int set_hpool_in_dhugetlb_pagelist(unsigned long idx, struct dhugetlb_poo return 0; }

-static struct dhugetlb_pool *find_hpool_by_dhugetlb_pagelist(struct page *page) +static struct dhugetlb_pool *get_hpool_from_pagelist(struct page *page) { unsigned long idx = hugepage_index(page_to_pfn(page)); struct dhugetlb_pool *hpool = NULL; @@ -513,6 +538,10 @@ static struct dhugetlb_pool *find_hpool_by_dhugetlb_pagelist(struct page *page) if (idx < dhugetlb_pagelist_t->count) hpool = dhugetlb_pagelist_t->hpool[idx]; read_unlock(&dhugetlb_pagelist_rwlock); + + if (!get_hpool_unless_zero(hpool)) + return NULL; + return hpool; }

@@ -523,27 +552,23 @@ bool page_belong_to_dynamic_hugetlb(struct page *page) if (!dhugetlb_enabled) return false;

- hpool = find_hpool_by_dhugetlb_pagelist(page); - if (hpool) - return true; - return false; + hpool = get_hpool_from_pagelist(page); + put_hpool(hpool); + + return !!hpool; }

static struct dhugetlb_pool *find_hpool_by_task(struct task_struct *tsk) { - struct mem_cgroup *memcg; + struct dhugetlb_pool *hpool;

if (!dhugetlb_enabled) return NULL;

- rcu_read_lock(); - memcg = mem_cgroup_from_task(tsk); - rcu_read_unlock(); - - if (!memcg) - return NULL; + hpool = get_hpool_from_task(tsk); + put_hpool(hpool);

- return memcg->hpool; + return hpool; }

int task_has_mem_in_hpool(struct task_struct *tsk) @@ -583,9 +608,8 @@ static struct page *__alloc_page_from_dhugetlb_pool(void) struct page *page = NULL; unsigned long flags;

- hpool = find_hpool_by_task(current); - - if (!get_hpool_unless_zero(hpool)) + hpool = get_hpool_from_task(current); + if (!hpool) return NULL;

if (hpool->normal_pages_disabled) @@ -655,9 +679,8 @@ static void __free_page_to_dhugetlb_pool(struct page *page) struct dhugetlb_pool *hpool; unsigned long flags;

- hpool = find_hpool_by_dhugetlb_pagelist(page); - - if (!get_hpool_unless_zero(hpool)) { + hpool = get_hpool_from_pagelist(page); + if (!hpool) { pr_err("dhugetlb: free error: get hpool failed\n"); return; } @@ -715,13 +738,10 @@ void link_hpool(struct hugetlbfs_inode_info *p, struct hstate *h) return;

size = huge_page_size(h); - if (size == PMD_SIZE || size == PUD_SIZE) { - p->hpool = find_hpool_by_task(current); - if (!get_hpool_unless_zero(p->hpool)) - p->hpool = NULL; - } else { + if (size == PMD_SIZE || size == PUD_SIZE) + p->hpool = get_hpool_from_task(current); + else p->hpool = NULL; - } }

void unlink_hpool(struct hugetlbfs_inode_info *p) @@ -822,9 +842,8 @@ void free_huge_page_to_dhugetlb_pool(struct page *page, bool restore_reserve) struct dhugetlb_pool *hpool; unsigned long flags;

- hpool = find_hpool_by_dhugetlb_pagelist(page); - - if (!get_hpool_unless_zero(hpool)) { + hpool = get_hpool_from_pagelist(page); + if (!hpool) { pr_err("dhugetlb: free error: get hpool failed\n"); return; } @@ -1024,7 +1043,7 @@ static int hugetlb_pool_update(struct mem_cgroup *memcg, int ret = -EINVAL;

again: - hpool = memcg->hpool; + hpool = get_hpool_from_memcg(memcg); if (!hpool) { ret = hugetlb_pool_create(memcg, nid); if (ret) @@ -1032,8 +1051,6 @@ static int hugetlb_pool_update(struct mem_cgroup *memcg, new_create = true; goto again; } - if (!get_hpool_unless_zero(hpool)) - return -EINVAL;

if (hpool->attach_memcg != memcg || hpool->nid != nid) goto out; @@ -1060,7 +1077,7 @@ bool dhugetlb_hide_files(struct cftype *cft)

static ssize_t update_reserved_pages(struct mem_cgroup *memcg, char *buf, int hpages_pool_idx) { - struct dhugetlb_pool *hpool = memcg->hpool; + struct dhugetlb_pool *hpool; struct huge_pages_pool *hpages_pool; unsigned long nr_pages; unsigned long delta; @@ -1074,7 +1091,8 @@ static ssize_t update_reserved_pages(struct mem_cgroup *memcg, char *buf, int hp if (*endp != '\0') return -EINVAL;

- if (!get_hpool_unless_zero(hpool)) + hpool = get_hpool_from_memcg(memcg); + if (!hpool) return -EINVAL;

mutex_lock(&hpool->reserved_lock); @@ -1138,14 +1156,20 @@ int normal_pages_disabled_write(struct cgroup_subsys_state *css, struct cftype *cft, u64 val) { struct mem_cgroup *memcg = mem_cgroup_from_css(css); - struct dhugetlb_pool *hpool = memcg->hpool; + struct dhugetlb_pool *hpool;

- if (!dhugetlb_enabled || !hpool) + if (!dhugetlb_enabled) return -EINVAL; if (!((val == 0) || (val == 1))) return -EINVAL;

+ hpool = get_hpool_from_memcg(memcg); + if (!hpool) + return -EINVAL; + hpool->normal_pages_disabled = val; + + put_hpool(hpool); return 0; }

@@ -1153,12 +1177,20 @@ u64 normal_pages_disabled_read(struct cgroup_subsys_state *css, struct cftype *cft) { struct mem_cgroup *memcg = mem_cgroup_from_css(css); - struct dhugetlb_pool *hpool = memcg->hpool; + struct dhugetlb_pool *hpool; + u64 val;

- if (!dhugetlb_enabled || !hpool) + if (!dhugetlb_enabled) return 0;

- return hpool->normal_pages_disabled; + hpool = get_hpool_from_memcg(memcg); + if (!hpool) + return 0; + + val = hpool->normal_pages_disabled; + + put_hpool(hpool); + return val; }

ssize_t write_hugepage_to_hpool(struct kernfs_open_file *of, @@ -1190,22 +1222,19 @@ ssize_t write_hugepage_to_hpool(struct kernfs_open_file *of, int hugetlb_pool_info_show(struct seq_file *m, void *v) { struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(m)); - struct dhugetlb_pool *hpool = memcg ? memcg->hpool : NULL; - unsigned long free_pages; - long used_pages = 0; + struct dhugetlb_pool *hpool; + unsigned long free_pages = 0, used_pages = 0; int i;

if (!dhugetlb_enabled) return 0;

+ hpool = get_hpool_from_memcg(memcg); if (!hpool) { seq_printf(m, "Current hierarchial have not memory pool.\n"); return 0; }

- if (!get_hpool_unless_zero(hpool)) - return 0; - dhugetlb_lock_all(hpool);

free_pages = hpool->hpages_pool[HUGE_PAGES_POOL_4K].free_normal_pages;

-- 2.25.1

Liu Shixin

4:02 p.m.

New subject: [PATCH OLK-5.10 2/2] mm/dynamic_hugetlb: use rcu lock to protect hpool

Offering: HULK hulk inclusion category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IA53JK

--------------------------------

In freeing process, set memcg->hpool to NULL and then freeing it. To avoid UAF problem of hpool, we have to make sure the users that already hold pointer to hpool don't use the pointer after freeing hpool. The freeing of hpool should block until make sure all such users don't use hpool. Since anyone who want to use hpool have to increase its refcount at first. Use rcu_read_lock() and synchronize_rcu() to guarantee all such users failed to get hpool before freeing hpool.

Fixes: a8a836a36072 ("mm/dynamic_hugetlb: establish the dynamic hugetlb feature framework") Signed-off-by: Liu Shixin liushixin2@huawei.com --- mm/dynamic_hugetlb.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/mm/dynamic_hugetlb.c b/mm/dynamic_hugetlb.c index f6c4c01eae8e..a88b02fef483 100644 --- a/mm/dynamic_hugetlb.c +++ b/mm/dynamic_hugetlb.c @@ -453,6 +453,7 @@ static void put_hpool(struct dhugetlb_pool *hpool) return; if (atomic_dec_and_test(&hpool->refcnt)) { css_put(&hpool->attach_memcg->css); + synchronize_rcu(); kfree(hpool); } } @@ -469,9 +470,11 @@ static struct dhugetlb_pool *get_hpool_from_memcg(struct mem_cgroup *memcg) { struct dhugetlb_pool *hpool;

+ rcu_read_lock(); hpool = memcg->hpool; if (!get_hpool_unless_zero(hpool)) hpool = NULL; + rcu_read_unlock();

return hpool; } @@ -479,15 +482,19 @@ static struct dhugetlb_pool *get_hpool_from_memcg(struct mem_cgroup *memcg) static struct dhugetlb_pool *get_hpool_from_task(struct task_struct *tsk) { struct mem_cgroup *memcg; + struct dhugetlb_pool *hpool;

rcu_read_lock(); memcg = mem_cgroup_from_task(tsk); - rcu_read_unlock(); - - if (!memcg) + if (!memcg || !css_tryget(&memcg->css)) { + rcu_read_unlock(); return NULL; + } + rcu_read_unlock();

- return get_hpool_from_memcg(memcg); + hpool = get_hpool_from_memcg(memcg); + css_put(&memcg->css); + return hpool; }

static int set_hpool_in_dhugetlb_pagelist(unsigned long idx, struct dhugetlb_pool *hpool)

-- 2.25.1

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