From 10d04c26ab2b7da31dd66973f5a09d6fd8ff2a46 Mon Sep 17 00:00:00 2001 From: Christoph Berg Date: Tue, 24 Jun 2025 16:44:27 +0200 Subject: [PATCH] mm/migrate: fix do_pages_stat in compat mode For arrays with more than 16 entries, the old code would incorrectly advance the pages pointer by 16 words instead of 16 compat_uptr_t. Fix by doing the pointer arithmetic inside get_compat_pages_array where pages32 is already a correctly-typed pointer. Discovered while working on PostgreSQL 18's new NUMA introspection code. Link: https://lkml.kernel.org/r/aGREU0XTB48w9CwN@msg.df7cb.de Fixes: 5b1b561ba73c ("mm: simplify compat_sys_move_pages") Signed-off-by: Christoph Berg Acked-by: David Hildenbrand Suggested-by: David Hildenbrand Reported-by: Bertrand Drouvot Reported-by: Tomas Vondra Closes: https://www.postgresql.org/message-id/flat/6342f601-77de-4ee0-8c2a-3deb50ceac5b%40vondra.me#86402e3d80c031788f5f55b42c459471 Cc: Alistair Popple Cc: Byungchul Park Cc: Gregory Price Cc: "Huang, Ying" Cc: Joshua Hahn Cc: Mathew Brost Cc: Rakie Kim Cc: Zi Yan Signed-off-by: Andrew Morton --- mm/migrate.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/mm/migrate.c b/mm/migrate.c index 8cf0f9c9599d..2c88f3b33833 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -2399,6 +2399,7 @@ set_status: static int get_compat_pages_array(const void __user *chunk_pages[], const void __user * __user *pages, + unsigned long chunk_offset, unsigned long chunk_nr) { compat_uptr_t __user *pages32 = (compat_uptr_t __user *)pages; @@ -2406,7 +2407,7 @@ static int get_compat_pages_array(const void __user *chunk_pages[], int i; for (i = 0; i < chunk_nr; i++) { - if (get_user(p, pages32 + i)) + if (get_user(p, pages32 + chunk_offset + i)) return -EFAULT; chunk_pages[i] = compat_ptr(p); } @@ -2425,27 +2426,28 @@ static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages, #define DO_PAGES_STAT_CHUNK_NR 16UL const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR]; int chunk_status[DO_PAGES_STAT_CHUNK_NR]; + unsigned long chunk_offset = 0; while (nr_pages) { unsigned long chunk_nr = min(nr_pages, DO_PAGES_STAT_CHUNK_NR); if (in_compat_syscall()) { if (get_compat_pages_array(chunk_pages, pages, - chunk_nr)) + chunk_offset, chunk_nr)) break; } else { - if (copy_from_user(chunk_pages, pages, + if (copy_from_user(chunk_pages, pages + chunk_offset, chunk_nr * sizeof(*chunk_pages))) break; } do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status); - if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status))) + if (copy_to_user(status + chunk_offset, chunk_status, + chunk_nr * sizeof(*status))) break; - pages += chunk_nr; - status += chunk_nr; + chunk_offset += chunk_nr; nr_pages -= chunk_nr; } return nr_pages ? -EFAULT : 0; -- 2.25.1