In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
drm\/pagemap: Prevent double migration of device pages<\/p>\n
A device-private folio migrated to system memory by a CPU fault can
\nremain reachable through the raw-PFN eviction path until migration
\nfinalization drops the source reference.<\/p>\n
If eviction selects the same device-private folio during this window,
\nit can attempt to migrate the folio again. The second migration can leave
\nan uncharged folio on an LRU list, causing folio_lruvec_lock_irqsave() to
\nretry indefinitely and resulting in a soft lockup and RCU stall.<\/p>\n
Mark successfully migrated device-private folios using a low bit of
\ntheir zone_device_data before migration finalization. Make both CPU-fault
\nand raw-PFN migration paths skip device-private folios carrying this
\nflag.<\/p>\n
Mask the flag when retrieving the drm_pagemap_zdd pointer and preserve
\nit when a device-private folio is split. Keeping the state on the physical
\nfolio also avoids depending on a virtual address that may change before a
\nfault occurs.<\/p>\n
v2:
\n– Replace the retired-PFN XArray with an embedded bitmap. (Matthew Brost)
\n– Mark every base page covered by a migrated folio so retirement remains
\n valid if the folio is later split.<\/p>\n
v3:
\n– Store the migrated state in a low bit of zone_device_data instead of
\n adding virtual-range and bitmap tracking to the ZDD. (Matthew Brost)
\n– Mask the flag when retrieving the ZDD and preserve it when splitting
\n a folio.
\n– Drop the pre-existing fixes already covered by Matthew Brost’s series:
\n https:\/\/patchwork.freedesktop.org\/series\/171651\/<\/p>\n
v4:
\n– Advance by the folio size only for migration entries marked with
\n MIGRATE_PFN_COMPOUND. (Sashiko)<\/p>\n
v5:
\n– Simplify ZDD flag updates and folio iteration. (Matthew Brost)
\n– Skip retired device-private folios in the CPU-fault path. (Matthew Brost)
\n– Preserve flag bits while taking a new ZDD reference for split folios.<\/p>\n
v6:
\n– Restore MIGRATE_PFN_COMPOUND-aware stepping so non-compound migration
\n entries are processed one at a time. (Sashiko)
\n– Drop the pre-existing fixes already covered by Matthew Brost’s series:
\n https:\/\/patchwork.freedesktop.org\/series\/171651\/<\/p>\n
The lockup was observed as:
\n[10109.860465] watchdog: BUG: soft lockup – CPU#9 stuck for 26s! [kworker\/u65:5:6557]
\n[10109.860524] Tainted: [S]=CPU_OUT_OF_SPEC, [O]=OOT_MODULE
\n[10109.860524] Hardware name: ASUS System Product Name\/PRIME Z790-P WIFI, BIOS 0812 02\/24\/2023
\n[10109.860525] Workqueue: xe_page_fault_work_queue xe_pagefault_queue_work [xe]
\n[10109.860644] RIP: 0010:_raw_spin_unlock_irqrestore+0x57\/0x80
\n[10109.860655] Call Trace:
\n[10109.860655]
\n[10109.860657] folio_lruvec_lock_irqsave+0x216\/0x220
\n[10109.860661] ? __pfx_lru_add+0x10\/0x10
\n[10109.860665] folio_batch_move_lru+0xc8\/0x450
\n[10109.860670] ? lock_acquire+0xc4\/0x2d0
\n[10109.860674] ? __folio_batch_add_and_move+0x60\/0x2e0
\n[10109.860677] ? folio_migrate_mapping+0xa6\/0x110
\n[10109.860679] ? folio_migrate_flags+0x13b\/0x1b0
\n[10109.860681] ? __pfx_lru_add+0x10\/0x10
\n[10109.860683] __folio_batch_add_and_move+0xe7\/0x2e0
\n[10109.860685] ? dma_iova_try_alloc+0xb0\/0x140
\n[10109.860689] folio_add_lru+0x64\/0x80
\n[10109.860691] __migrate_device_finalize+0x12c\/0x270
\n[10109.860695] migrate_device_finalize+0x10\/0x20
\n[10109.860698] drm_pagemap_evict_to_ram+0x185\/0x370 [drm_gpusvm_helper]
\n[10109.860704] ? drm_pagemap_evict_to_ram+0x96\/0x370 [drm_gpusvm_helper]
\n[10109.860709] xe_svm_bo_evict+0x15\/0x20 [xe]
\n[10109.860819] ? xe_svm_bo_evict+0x15\/0x20 [xe]
\n[10109.860921] xe_bo_move+0x107e\/0x1570 [xe]
\n[10109.860992] ? xe_ttm_tt_create+0x168\/0x340 [xe]
\n[10109.861059] ? __up_read+0x98\/0x2b0
\n[10109.861061] ? lock_is_held_type+0xa3\/0x130
\n[10109.861067] ttm_bo_handle_move_mem+0xe8\/0x1e0 [ttm]
\n[10109.861075] ttm_bo_evict+0x141\/0x1c0 [ttm]
\n[10109.861081] ttm_bo_evict_cb+0x9f\/0x100 [ttm]
\n[10109.861086] ttm_lru_walk_for_evict+0x84\/0x190 [ttm]
\n[10109.861091] ? xe_ttm_vram_mgr_new+0x258\/0x3a0 [xe]
\n[10109.861198] ttm_bo_alloc_resource+0x219\/0
\n—truncated—<\/p>\n","protected":false},"excerpt":{"rendered":"
In the Linux kernel, the following vulnerability has been resolved:<\/p>\n
drm\/pagemap: Prevent double migration of device pages<\/p>\n
A device-private folio migrated to system memory by a CPU fault can
\nremain r<\/p>\n","protected":false},"template":"","meta":[],"categories":[],"tags":[],"class_list":["post-29260","vuln","type-vuln","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln\/29260","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/vuln"}],"about":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=\/wp\/v2\/types\/vuln"}],"wp:attachment":[{"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=29260"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=29260"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.54iter.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=29260"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}