{ "schema_version": "1.6.1", "id": "RPI-CVE-2026-98818", "modified": "2026-10-19T04:30:01Z", "upstream": [ "CVE-2026-98818" ], "published": "2026-10-18T15:54:51Z", "summary": "mm/slab: do not wake up kswapd in __kfree_rcu_sheaf()", "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/slab: do not wake up kswapd in __kfree_rcu_sheaf()\n\nSince kfree_rcu() can be called under pi_lock (a raw spinlock in the\nscheduler), kfree_rcu() itself should never allocate memory with\n__GFP_KSWAPD_RECLAIM as waking up kswapd ends up acquiring pi_lock,\nwhich leads to a deadlock.\n\nReproducing the issue even intentionally was not straightforward.\nThe set_cpus_allowed_force() path that is called under pi_lock is\nexercised very rarely, and competing tasks that allocate memory will\nmost likely wake kswapd up.\n\nTherefore the existence of the deadlock was verified with a modified\nkernel that has a lockdep map for waking up kswapd:\n\n ======================================================\n WARNING: possible circular locking dependency detected\n 7.2.0-rc1-slab-for-next+ #10 Not tainted\n ------------------------------------------------------\n git/6660 is trying to acquire lock:\n ffff8e524533c550 (&p->pi_lock){-.-.}-{2:2}, at: _raw_spin_lock_irqsave+0x12/0x20\n\n but task is already holding lock:\n ffff8e57bffff1a0 (&pgdat->kswapd_wait){....}-{3:3}, at: _raw_spin_lock_irqsave+0x12/0x20\n\n which lock already depends on the new lock.\n\n the existing dependency chain (in reverse order) is:\n\n -> #2 (&pgdat->kswapd_wait){....}-{3:3}:\n __lock_acquire+0x5a4/0xc50\n lock_acquire.part.0+0xb7/0x240\n lock_acquire+0x70/0x170\n __raw_spin_lock_irqsave+0x44/0x80\n _raw_spin_lock_irqsave+0x12/0x20\n __wake_up_common_lock+0x31/0xa0\n __wake_up+0x20/0x40\n kswapd_wakeup_wake+0x7e/0x110\n wakeup_kswapd+0x295/0x320\n wake_all_kswapds+0xac/0x1a0\n __alloc_pages_slowpath.constprop.0+0x282/0xf80\n __alloc_frozen_pages_noprof+0x32a/0x360\n alloc_slab_page+0x2e/0x160\n allocate_slab+0x82/0x420\n new_slab+0x52/0xb0\n refill_objects+0x13d/0x190\n refill_sheaf+0x5d/0xd0\n __pcs_replace_empty_main+0x230/0xb10\n [...]\n\n -> #1 (kswapd_wakeup){-.-.}-{0:0}:\n __lock_acquire+0x5a4/0xc50\n lock_sync.part.0+0x75/0x100\n lock_sync+0x36/0x70\n might_wakeup_kswapd+0x61/0xa0\n __kfree_rcu_sheaf+0x33/0xd90\n kvfree_call_rcu+0x1d4/0x3b0\n set_cpus_allowed_force+0x163/0x220\n cpuset_cpus_allowed_fallback+0x18b/0x240\n select_fallback_rq+0x1e6/0x250\n\t [...]\n\n -> #0 (&p->pi_lock){-.-.}-{2:2}:\n check_prev_add+0xe6/0xe00\n validate_chain+0x51e/0x6e0\n __lock_acquire+0x5a4/0xc50\n lock_acquire.part.0+0xb7/0x240\n lock_acquire+0x70/0x170\n __raw_spin_lock_irqsave+0x44/0x80\n _raw_spin_lock_irqsave+0x12/0x20\n try_to_wake_up+0x77/0xa90\n default_wake_function+0x27/0x60\n autoremove_wake_function+0x23/0xb0\n __wake_up_common+0xb8/0x170\n __wake_up_common_lock+0x51/0xa0\n __wake_up+0x20/0x40\n kswapd_wakeup_wake+0x7e/0x110\n wakeup_kswapd+0x295/0x320\n wake_all_kswapds+0xac/0x1a0\n __alloc_pages_slowpath.constprop.0+0x282/0xf80\n __alloc_frozen_pages_noprof+0x32a/0x360\n alloc_slab_page+0x2e/0x160\n allocate_slab+0x82/0x420\n new_slab+0x52/0xb0\n refill_objects+0x13d/0x190\n refill_sheaf+0x5d/0xd0\n __pcs_replace_empty_main+0x230/0xb10\n [...]\n\n other info that might help us debug this:\n\n Chain exists of:\n &p->pi_lock --> kswapd_wakeup --> &pgdat->kswapd_wait\n\n Possible unsafe locking scenario:\n\n CPU0 CPU1\n ---- ----\n lock(&pgdat->kswapd_wait);\n lock(kswapd_wakeup);\n lock(&pgdat->kswapd_wait);\n lock(&p->pi_lock);\n\n *** DEADLOCK ***\n\n 3 locks held by git/6660:\n #0: ffff8e519f0e9e20 (&type->i_mutex_dir_key#6){++++}-{4:4}, at: lookup_slow+0x2d/0x60\n #1: ffffffff8a31c460 (kswapd_wakeup){-.-.}-\n---truncated---", "affected": [ { "package": { "ecosystem": "Raspberry Pi OS:13", "name": "linux" }, "versions": [ "1:6.18.29-1+rpt1", "1:6.18.33-1+rpt1", "1:6.18.34-1+rpt1", "1:6.18.39-1+rpt1", "1:6.18.50-1+rpt1" ], "ecosystem_specific": { "binaries": [ { "binary_name": "linux-image-6.18.29+rpt-rpi-2712", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.29+rpt-rpi-v6", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.29+rpt-rpi-v7", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.29+rpt-rpi-v8", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.29+rpt-rpi-v8-rt", "binary_version": "1:6.18.29-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-2712", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-v6", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-v7", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-v8", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.33+rpt-rpi-v8-rt", "binary_version": "1:6.18.33-1+rpt1" }, { "binary_name": "linux-image-6.18.34+rpt-rpi-2712", "binary_version": "1:6.18.34-1+rpt1" }, { "binary_name": "linux-image-6.18.34+rpt-rpi-v6", "binary_version": "1:6.18.34-1+rpt1" }, { "binary_name": "linux-image-6.18.34+rpt-rpi-v7", "binary_version": "1:6.18.34-1+rpt1" }, { "binary_name": "linux-image-6.18.34+rpt-rpi-v8", "binary_version": "1:6.18.34-1+rpt1" }, { "binary_name": "linux-image-6.18.34+rpt-rpi-v8-rt", "binary_version": "1:6.18.34-1+rpt1" }, { "binary_name": "linux-image-6.18.39+rpt-rpi-2712", "binary_version": "1:6.18.39-1+rpt1" }, { "binary_name": "linux-image-6.18.39+rpt-rpi-v6", "binary_version": "1:6.18.39-1+rpt1" }, { "binary_name": "linux-image-6.18.39+rpt-rpi-v7", "binary_version": "1:6.18.39-1+rpt1" }, { "binary_name": "linux-image-6.18.39+rpt-rpi-v8", "binary_version": "1:6.18.39-1+rpt1" }, { "binary_name": "linux-image-6.18.39+rpt-rpi-v8-rt", "binary_version": "1:6.18.39-1+rpt1" }, { "binary_name": "linux-image-6.18.50+rpt-rpi-2712", "binary_version": "1:6.18.50-1+rpt1" }, { "binary_name": "linux-image-6.18.50+rpt-rpi-v6", "binary_version": "1:6.18.50-1+rpt1" }, { "binary_name": "linux-image-6.18.50+rpt-rpi-v7", "binary_version": "1:6.18.50-1+rpt1" }, { "binary_name": "linux-image-6.18.50+rpt-rpi-v8", "binary_version": "1:6.18.50-1+rpt1" }, { "binary_name": "linux-image-6.18.50+rpt-rpi-v8-rt", "binary_version": "1:6.18.50-1+rpt1" } ] }, "database_specific": { "per_version": { "1:6.18.29-1+rpt1": { "linux_commit": "66318c5b5cd8145a662303af12ed39ac07eb27cc", "upstream_version": "6.18.29", "assessment": "commit ancestry (strak rule)", "upstream_fixed": null }, "1:6.18.33-1+rpt1": { "linux_commit": "95b85bebbedcaedfa7ca79116ed38b7376fba412", "upstream_version": "6.18.33", "assessment": "commit ancestry (strak rule)", "upstream_fixed": null }, "1:6.18.34-1+rpt1": { "linux_commit": "c8c7494100e99ee05b11aaa4f0588a223a63d1af", "upstream_version": "6.18.34", "assessment": "commit ancestry (strak rule)", "upstream_fixed": null }, "1:6.18.39-1+rpt1": { "linux_commit": "60ea684a8ace97bb0db1a16e20753bdd6ab371ff", "upstream_version": "6.18.39", "assessment": "commit ancestry (strak rule)", "upstream_fixed": null }, "1:6.18.50-1+rpt1": { "linux_commit": "cff533aec2fa601846766b32ff57204e0a61bed7", "upstream_version": "6.18.50", "assessment": "commit ancestry (strak rule)", "upstream_fixed": null } } } } ], "references": [ { "type": "ADVISORY", "url": "https://www.cve.org/CVERecord?id=CVE-2026-98818" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/46545c86b54ffb969b6e3662942b4a6191619eaa" }, { "type": "FIX", "url": "https://git.kernel.org/stable/c/af2fb3ee6679b517e2fdbd3ba16ec276a8b74312" } ], "database_specific": { "source": "https://git.kernel.org/pub/scm/linux/security/vulns.git", "upstream_modified": "2026-10-18T15:54:51Z" } }