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a=ed25519-sha256; t=1774604917; l=2959; i=shivamkalra98@zohomail.in; s=20260212; h=from:subject:message-id; bh=q4Ito1vUmJmb3A3de47pGFK3WSX+j54Hs6oFM89TDPE=; b=WAfAOXMaxhCxjvt2ewSFJ24eqk8Y14S2Fzvr0Bi6nQKMPvQrC4YQDdEU9hGatJ8o3viLlAzov V4kYd9euOsHDeADLt//193DDbkOHhKjTrrbTTQyhPFP8B9THCu6sr/a X-Developer-Key: i=shivamkalra98@zohomail.in; a=ed25519; pk=9Q+S1LD/xjbjL7bEaLIlwRADBwU/6LJq7lYm8LFrkQE= X-Endpoint-Received: by B4 Relay for shivamkalra98@zohomail.in/20260212 with auth_id=633 X-Original-From: Shivam Kalra Reply-To: shivamkalra98@zohomail.in X-Rspamd-Queue-Id: 4C56DA0002 X-Stat-Signature: sufp451m3triq15jwqcmu3uknegpd5tk X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1774604921-856198 X-HE-Meta: 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 hae5nO5l Hhn2jMbRJMiHsFnrltDVbc+pM4jVIAR5luhemsm8yCD8AgudJR+oi8tSbAInbeG9u/by6Qy5w0RDGC4Fo2P6T8iIVp9lsfapebdOs/7F17969ZnNutepI7TJWTBBacdxvdrRX7wakNhCBxQNZSb1MBu+f61QLwpJbsqoLSxdAMGK5ODKCsHUM4Ojz6DsRHwdItotuYxm0O7p3L9cxvmZcJ6lL0bcS4TxkaKkSmusKlKeNvLxDIuQpPSjBNi7P8B5OJDkL5u9tUuB2zDmeOXYYRLLmPX+oaykw12JqkU4jsNRRd1Erk8V5M3ob4A+EiB73bqG/n34eABOVFZw3+K70fp5gRvwdsb+J/d/ZVL7x+15d3mwlvv49wV8owt4JVgRzbeVN1hEfbwVdBh4pvn9fkYmJUW3IqLaescsf Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: Shivam Kalra The vmalloc status readers (vmalloc_info_show(), show_numa_info(), and vmalloc_dump_obj()) currently read v->nr_pages and the v->pages array without any concurrent protection. In preparation for vrealloc() shrink support, where v->nr_pages can be decreased and entries in the v->pages array can be nulled out concurrently, these readers must be protected to prevent use-after-free or NULL pointer dereferences. Update these functions to use READ_ONCE() when accessing v->nr_pages and v->pages[nr]. This ensures the compiler does not re-fetch these values and provides a consistent view of the vmap area's state. Additionally, in show_numa_info(), explicitly check for a NULL page pointer before dereferencing it to avoid potential crashes if a page was concurrently removed during a shrink operation. Signed-off-by: Shivam Kalra --- mm/vmalloc.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index ddb689bf9ba5..c6bdddee6266 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -5189,7 +5189,7 @@ bool vmalloc_dump_obj(void *object) vm = va->vm; addr = (unsigned long) vm->addr; caller = vm->caller; - nr_pages = vm->nr_pages; + nr_pages = READ_ONCE(vm->nr_pages); spin_unlock(&vn->busy.lock); pr_cont(" %u-page vmalloc region starting at %#lx allocated at %pS\n", @@ -5210,7 +5210,7 @@ bool vmalloc_dump_obj(void *object) static void show_numa_info(struct seq_file *m, struct vm_struct *v, unsigned int *counters) { - unsigned int nr; + unsigned int nr, nr_pages; unsigned int step = 1U << vm_area_page_order(v); if (!counters) @@ -5218,8 +5218,13 @@ static void show_numa_info(struct seq_file *m, struct vm_struct *v, memset(counters, 0, nr_node_ids * sizeof(unsigned int)); - for (nr = 0; nr < v->nr_pages; nr += step) - counters[page_to_nid(v->pages[nr])] += step; + nr_pages = READ_ONCE(v->nr_pages); + for (nr = 0; nr < nr_pages; nr += step) { + struct page *page = READ_ONCE(v->pages[nr]); + + if (page) + counters[page_to_nid(page)] += step; + } for_each_node_state(nr, N_HIGH_MEMORY) if (counters[nr]) seq_printf(m, " N%u=%u", nr, counters[nr]); @@ -5247,6 +5252,7 @@ static int vmalloc_info_show(struct seq_file *m, void *p) struct vmap_area *va; struct vm_struct *v; unsigned int *counters; + unsigned int nr_pages; if (IS_ENABLED(CONFIG_NUMA)) counters = kmalloc_array(nr_node_ids, sizeof(unsigned int), GFP_KERNEL); @@ -5276,8 +5282,9 @@ static int vmalloc_info_show(struct seq_file *m, void *p) if (v->caller) seq_printf(m, " %pS", v->caller); - if (v->nr_pages) - seq_printf(m, " pages=%d", v->nr_pages); + nr_pages = READ_ONCE(v->nr_pages); + if (nr_pages) + seq_printf(m, " pages=%d", nr_pages); if (v->phys_addr) seq_printf(m, " phys=%pa", &v->phys_addr); -- 2.43.0