damon_migrate_pages() tries migration even if the target node is invalid. If users mistakenly make such invalid requests via DAMOS_MIGRATE_{HOT,COLD} action, the below kernel BUG can happen.
[ 7831.883495] BUG: unable to handle page fault for address: 0000000000001f48 [ 7831.884160] #PF: supervisor read access in kernel mode [ 7831.884681] #PF: error_code(0x0000) - not-present page [ 7831.885203] PGD 0 P4D 0 [ 7831.885468] Oops: Oops: 0000 [#1] SMP PTI [ 7831.885852] CPU: 31 UID: 0 PID: 94202 Comm: kdamond.0 Not tainted 6.16.0-rc5-mm-new-damon+ #93 PREEMPT(voluntary) [ 7831.886913] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-4.el9 04/01/2014 [ 7831.887777] RIP: 0010:__alloc_frozen_pages_noprof (include/linux/mmzone.h:1724 include/linux/mmzone.h:1750 mm/page_alloc.c:4936 mm/page_alloc.c:5137) [...] [ 7831.895953] Call Trace: [ 7831.896195] <TASK> [ 7831.896397] __folio_alloc_noprof (mm/page_alloc.c:5183 mm/page_alloc.c:5192) [ 7831.896787] migrate_pages_batch (mm/migrate.c:1189 mm/migrate.c:1851) [ 7831.897228] ? __pfx_alloc_migration_target (mm/migrate.c:2137) [ 7831.897735] migrate_pages (mm/migrate.c:2078) [ 7831.898141] ? __pfx_alloc_migration_target (mm/migrate.c:2137) [ 7831.898664] damon_migrate_folio_list (mm/damon/ops-common.c:321 mm/damon/ops-common.c:354) [ 7831.899140] damon_migrate_pages (mm/damon/ops-common.c:405) [...]
Add a target node validity check in damon_migrate_pages(). The validity check is stolen from that of do_pages_move(), which is being used for the move_pages() system call.
Link: https://lkml.kernel.org/r/20250720185822.1451-1-sj@kernel.org Fixes: b51820ebea65 ("mm/damon/paddr: introduce DAMOS_MIGRATE_COLD action for demotion") [6.11.x] Signed-off-by: SeongJae Park sj@kernel.org Reviewed-by: Joshua Hahn joshua.hahnjy@gmail.com Cc: Honggyu Kim honggyu.kim@sk.com Cc: Hyeongtak Ji hyeongtak.ji@sk.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org (cherry picked from commit 7e6c3130690a01076efdf45aa02ba5d5c16849a0) Signed-off-by: SeongJae Park sj@kernel.org --- mm/damon/paddr.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c index 1b70d3f36046..32ee3739f1d2 100644 --- a/mm/damon/paddr.c +++ b/mm/damon/paddr.c @@ -476,6 +476,10 @@ static unsigned long damon_pa_migrate_pages(struct list_head *folio_list, if (list_empty(folio_list)) return nr_migrated;
+ if (target_nid < 0 || target_nid >= MAX_NUMNODES || + !node_state(target_nid, N_MEMORY)) + return nr_migrated; + noreclaim_flag = memalloc_noreclaim_save();
nid = folio_nid(lru_to_folio(folio_list));