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Tue, 30 Sep 2025 18:06:56 -0700 (PDT) Received: from localhost ([185.92.221.13]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b3545a96977sm1258180066b.93.2025.09.30.18.06.55 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Tue, 30 Sep 2025 18:06:56 -0700 (PDT) From: Wei Yang To: akpm@linux-foundation.org, david@redhat.com, lorenzo.stoakes@oracle.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, xu.xin16@zte.com.cn, chengming.zhou@linux.dev Cc: linux-mm@kvack.org, kirill@shutemov.name, raghavendra.kt@amd.com, Wei Yang , Dan Carpenter Subject: [Patch mm-stable-fixup 1/2] mm/ksm: don't call mm_slot_entry() when the slot is NULL Date: Wed, 1 Oct 2025 01:06:50 +0000 Message-Id: <20251001010651.10543-2-richard.weiyang@gmail.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20251001010651.10543-1-richard.weiyang@gmail.com> References: <20251001010651.10543-1-richard.weiyang@gmail.com> X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 4A14B180005 X-Stat-Signature: spb8b4tuwxbzypgfcfp4q3x8z59awisf X-Rspam-User: X-HE-Tag: 1759280818-424090 X-HE-Meta: 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 torH3Tti 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: When using mm_slot in ksm, there is code like: slot = mm_slot_lookup(mm_slots_hash, mm); mm_slot = mm_slot_entry(slot, struct ksm_mm_slot, slot); if (mm_slot && ..) { } The mm_slot_entry() won't return a valid value if slot is NULL generally. But currently it works since slot is the first element of struct ksm_mm_slot. To reduce the ambiguity and make it robust, only call mm_slot_entry() when we have a valid slot. Signed-off-by: Wei Yang Cc: David Hildenbrand Cc: Dev Jain Cc: Lance Yang Cc: Kiryl Shutsemau Cc: xu xin Cc: Dan Carpenter Cc: Chengming Zhou Reviewed-by: Dev Jain Acked-by: David Hildenbrand Acked-by: Kiryl Shutsemau Acked-by: Zi Yan --- mm/ksm.c | 27 ++++++++++++++------------- 1 file changed, 14 insertions(+), 13 deletions(-) diff --git a/mm/ksm.c b/mm/ksm.c index 04019a15b25d..7bc726b50b2f 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -2921,7 +2921,7 @@ int __ksm_enter(struct mm_struct *mm) void __ksm_exit(struct mm_struct *mm) { - struct ksm_mm_slot *mm_slot; + struct ksm_mm_slot *mm_slot = NULL; struct mm_slot *slot; int easy_to_free = 0; @@ -2936,19 +2936,20 @@ void __ksm_exit(struct mm_struct *mm) spin_lock(&ksm_mmlist_lock); slot = mm_slot_lookup(mm_slots_hash, mm); - if (slot) { - mm_slot = mm_slot_entry(slot, struct ksm_mm_slot, slot); - if (ksm_scan.mm_slot != mm_slot) { - if (!mm_slot->rmap_list) { - hash_del(&slot->hash); - list_del(&slot->mm_node); - easy_to_free = 1; - } else { - list_move(&slot->mm_node, - &ksm_scan.mm_slot->slot.mm_node); - } - } + if (!slot) + goto unlock; + mm_slot = mm_slot_entry(slot, struct ksm_mm_slot, slot); + if (ksm_scan.mm_slot == mm_slot) + goto unlock; + if (!mm_slot->rmap_list) { + hash_del(&slot->hash); + list_del(&slot->mm_node); + easy_to_free = 1; + } else { + list_move(&slot->mm_node, + &ksm_scan.mm_slot->slot.mm_node); } +unlock: spin_unlock(&ksm_mmlist_lock); if (easy_to_free) { -- 2.34.1