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b=tNizQ9Cz4zFrx+Aab+u/InMxiwoNYZQGZz/rYK7u+uYTkpwHGi7dHkFVAGf0CkQJ0 Y8pRjFcAzj95DJOxx98TxAdIe0sHJtASEgP572Tz+UX/FecRBmhr4A9a739ETiTn3c SVIcJ9OO6PKVjKcG4W/LWHhqifgSOIHCEBl74venwHcvXb7AVhvQHwLZnnq0t+gAFW /MQ89ixqGCp/z8pwiqGRE1YryoI9ddd5OJv5pk1VQ+66gS+9XfWQM4NhoibsItxduS sCnuOjo7wCq0YaLBM46NZf6Zbfb79/Dc4814+MZkNATA0bfUMhfMlBU1xhxn1LqLxr UqRQbPqmhFYvA== Message-ID: <7e86e2f0-e581-4772-b468-1da04a214f07@kernel.org> Date: Mon, 9 Feb 2026 20:46:06 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] mm/page_alloc: clear page->private in free_pages_prepare() To: Mikhail Gavrilov , linux-mm@kvack.org Cc: akpm@linux-foundation.org, vbabka@suse.cz, surenb@google.com, mhocko@suse.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, npiggin@gmail.com, linux-kernel@vger.kernel.org, kasong@tencent.com, hughd@google.com, chrisl@kernel.org, ryncsn@gmail.com, stable@vger.kernel.org, willy@infradead.org References: <209207FE-D3A9-4BE2-8DA7-9BE38A19F387@nvidia.com> <20260207173615.146159-1-mikhail.v.gavrilov@gmail.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 1717F1C000E X-Stat-Signature: bpawquq9rpjikcg51pnpqo74hg15o8qs X-Rspam-User: X-HE-Tag: 1770666373-62499 X-HE-Meta: U2FsdGVkX1+Fy1s1EepD1OI4y7T1+6C0FbORqNfp6IYMKMiDQfAP2OfJcUe337R4ROo8e14n9FNkaL6yeCB2Nq4OA0DashFFfd645dsqMKpamquc7SaRbAplpjuDhQ4tpqUjTsG1u0AbjSnMFSe0ZO5hGlu+tgMOuIFRfUD//OlSMseFb7rMdJXFepXBv6sktCcymuvtVq48r1D2YVBPB6OlJPmV2I46R5O2wNdhDLA+Aq616rf483XmUWaIYx6Gl4gUnIAT3ZIYfwhjcLL4TykJ8IR7X/RpcE/7HHKQNKIMRaalElWGI/lM2VIqmBfpUaDdrq59eK4UqoQbltpsXQYd9uVvneu0W09vfFTY2kk+KlQmVmsM7szEyLDeWicqI/oV2SzapDWS7k26PFTCrfNNgnYN9NWphdTP2vB2yC/P9wtW6mV0Vpip98cEXqmkCARKpKPv5yX3n9h/Im1AnSJ6inink2BMUZLVFLkECoQLXE7LZ4wmLxz9uC/rpHTHX6UVfoHaSiPIpVSYMdg46omC+yfg2epsfHYRELaVAbBUkFY6m9PyB3ZM+79Uy2LhpXftxhm9IDvubbTbvS5l/tQTuN5qoXFZTfS/CbGQo437OnYSX+BgUNH+JCD07Y0cCcEi4RLsULclk2yoCv2TVf0G2zWBqgO4XhLnm20Iy7GwPYlnK4XzvYnK18fNigDvVSTh0KT13+VSmlu9RLV+3tALNnGAIeMTeVOrJpDroVzZfaEVdaDL8nWiyXFWFG2r83OnHB04ybvjKn8+2GpMmtL0JfsKiwgEnT4U4c+bWGmoPGxm8NXOvyc7oVSve+IcjV2cehTPuvarhGi699Xq4er2dOM7QHThunD6Bg5IAKBh8S7upJuWRD3hhUTAHHwxv0wlf+6qbZEShJWcflE7QbS8I+qL9awUGF1qY841EbQ3dUqsw/zIC4hvaIMG/oKaYA8WEVLNMoip/P61Zxb ZQ9HRzqu w2zkOCgaV+cNMZKqKDPvE0QSDB5mlwLJrg+UXi79zmGc+NTEHwVqsAZZ8Oc3Fq3NL3+N0WIKEtoJ+bJ7bHIDesJYGoY4WFuCi4ei81LrPLoffE1UltrYB2h2qSPSk6qw/lHvb8isK9zgBsk7Nsapcgx6S4LYxKHFhwTNntcDWf1k0/Dbf4ITB7uHgfwAbY6y/cl4UwgjjQrTvDwKMDzzOFSDEhBP0lovhtnl4Vl4GVGfQ45QW2C5J7E+C/3z9Fv8+dbXzt7WQakaH2mnD3KR7UJKVGVnfNv2qdldYbl/6G1z+Q1aAeuBEZ7kqdu+vmHtm2Kts8ar3X2S9CudfqB2Jgk5NRnZO9Nkoh9cmLAtGOjcLbsQIZwZ1VMmniunuenjOpZbBRTkuPlq4jjF0a5h8NA/0Ncf5aP134/MD0eyiGVKuKR5z1Qp5jtQP2Ah9kGOIcG8C 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: On 2/7/26 18:36, Mikhail Gavrilov wrote: > Several subsystems (slub, shmem, ttm, etc.) use page->private but don't > clear it before freeing pages. When these pages are later allocated as > high-order pages and split via split_page(), tail pages retain stale > page->private values. > > This causes a use-after-free in the swap subsystem. The swap code uses > page->private to track swap count continuations, assuming freshly > allocated pages have page->private == 0. When stale values are present, > swap_count_continued() incorrectly assumes the continuation list is valid > and iterates over uninitialized page->lru containing LIST_POISON values, > causing a crash: > > KASAN: maybe wild-memory-access in range [0xdead000000000100-0xdead000000000107] > RIP: 0010:__do_sys_swapoff+0x1151/0x1860 > > Fix this by clearing page->private in free_pages_prepare(), ensuring all > freed pages have clean state regardless of previous use. > > Fixes: 3b8000ae185c ("mm/vmalloc: huge vmalloc backing pages should be split rather than compound") > Cc: stable@vger.kernel.org > Suggested-by: Zi Yan > Acked-by: Zi Yan > Signed-off-by: Mikhail Gavrilov > --- Okay, let's do this as a fix, and cleanup the page->private handling separately. Thanks! Acked-by: David Hildenbrand (Arm) -- Cheers, David