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Mon, 9 Feb 2026 11:11:30 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id wlXuFOLAiWlPSgAAD6G6ig (envelope-from ); Mon, 09 Feb 2026 11:11:30 +0000 Message-ID: Date: Mon, 9 Feb 2026 12:11:30 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm/page_alloc: clear page->private in free_pages_prepare() Content-Language: en-US To: Mikhail Gavrilov , linux-mm@kvack.org Cc: akpm@linux-foundation.org, chrisl@kernel.org, kasong@tencent.com, hughd@google.com, ryncsn@gmail.com, ziy@nvidia.com, stable@vger.kernel.org References: <17A126A7-BACA-49E5-8A89-F8E665981136@nvidia.com> <20260207153716.59302-1-mikhail.v.gavrilov@gmail.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJnyBr8BQka0IFQAAoJECJPp+fMgqZkqmMQ AIbGN95ptUMUvo6aAdhxaOCHXp1DfIBuIOK/zpx8ylY4pOwu3GRe4dQ8u4XS9gaZ96Gj4bC+ jwWcSmn+TjtKW3rH1dRKopvC07tSJIGGVyw7ieV/5cbFffA8NL0ILowzVg8w1ipnz1VTkWDr 2zcfslxJsJ6vhXw5/npcY0ldeC1E8f6UUoa4eyoskd70vO0wOAoGd02ZkJoox3F5ODM0kjHu Y97VLOa3GG66lh+ZEelVZEujHfKceCw9G3PMvEzyLFbXvSOigZQMdKzQ8D/OChwqig8wFBmV QCPS4yDdmZP3oeDHRjJ9jvMUKoYODiNKsl2F+xXwyRM2qoKRqFlhCn4usVd1+wmv9iLV8nPs 2Db1ZIa49fJet3Sk3PN4bV1rAPuWvtbuTBN39Q/6MgkLTYHb84HyFKw14Rqe5YorrBLbF3rl M51Dpf6Egu1yTJDHCTEwePWug4XI11FT8lK0LNnHNpbhTCYRjX73iWOnFraJNcURld1jL1nV r/LRD+/e2gNtSTPK0Qkon6HcOBZnxRoqtazTU6YQRmGlT0v+rukj/cn5sToYibWLn+RoV1CE Qj6tApOiHBkpEsCzHGu+iDQ1WT0Idtdynst738f/uCeCMkdRu4WMZjteQaqvARFwCy3P/jpK uvzMtves5HvZw33ZwOtMCgbpce00DaET4y/UzsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZ8gcVAUJFhTonwAKCRAiT6fnzIKmZLY8D/9uo3Ut9yi2YCuASWxr7QQZ lJCViArjymbxYB5NdOeC50/0gnhK4pgdHlE2MdwF6o34x7TPFGpjNFvycZqccSQPJ/gibwNA zx3q9vJT4Vw+YbiyS53iSBLXMweeVV1Jd9IjAoL+EqB0cbxoFXvnjkvP1foiiF5r73jCd4PR rD+GoX5BZ7AZmFYmuJYBm28STM2NA6LhT0X+2su16f/HtummENKcMwom0hNu3MBNPUOrujtW khQrWcJNAAsy4yMoJ2Lw51T/5X5Hc7jQ9da9fyqu+phqlVtn70qpPvgWy4HRhr25fCAEXZDp xG4RNmTm+pqorHOqhBkI7wA7P/nyPo7ZEc3L+ZkQ37u0nlOyrjbNUniPGxPxv1imVq8IyycG AN5FaFxtiELK22gvudghLJaDiRBhn8/AhXc642/Z/yIpizE2xG4KU4AXzb6C+o7LX/WmmsWP Ly6jamSg6tvrdo4/e87lUedEqCtrp2o1xpn5zongf6cQkaLZKQcBQnPmgHO5OG8+50u88D9I rywqgzTUhHFKKF6/9L/lYtrNcHU8Z6Y4Ju/MLUiNYkmtrGIMnkjKCiRqlRrZE/v5YFHbayRD dJKXobXTtCBYpLJM4ZYRpGZXne/FAtWNe4KbNJJqxMvrTOrnIatPj8NhBVI0RSJRsbilh6TE m6M14QORSWTLRg== In-Reply-To: <20260207153716.59302-1-mikhail.v.gavrilov@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 6F0A92000E X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: 4knnzpsi6agpddu8a764n16hetin4cis X-HE-Tag: 1770635492-551487 X-HE-Meta: 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 G/tmHRH5 ndcLWlTWTPi/aEITUpHjb+c7yp42qhTD8iI3puE0c27PHH8gpsFJXq2lHJNFCNpWB3idWYD5XDZu/Ht23DnZgTp3tV6Er1afzUmLxx+Peg4rzQtZCOQV/HNN9vrVcF28q6zRt+vq4YMQ/M06gAuzbWHDzmj3tzFT5Rg6wfVOT3pjm0vkR3wwiILiunJT/DyGH7+y2PJyH38WAO5Pe9aq7W503tXZH9wBQwJF+FpTeWio5KCj25LB0nRr9EZDZtsnfahmkbpkfA4nZumMLOULz4mnppN+lbQQkA0MNH8p+QKRl8EVqeSap02qRb2Vhr7aNlC6Yx3+rJCvgA6jx5nVQXSSVRfy9d9NP8smnxA3PfDC4O5Av5pmKRmueNRkul3HYs9Tzyeo4YslJ8omgHJWrlSlQI3KS5Zujj51IT2SV6EHsF1tA4pEiQFbfG+0H1s278LknS4p+8MnfXkilXq8bBXHmaqEGvKdwFV9a 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 16:37, 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 > Signed-off-by: Mikhail Gavrilov Seems cheap enough and robust to just do it. Could be different for tail pages (although we do modify them too anyway). Reviewed-by: Vlastimil Babka > --- > mm/page_alloc.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index cbf758e27aa2..24ac34199f95 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1430,6 +1430,7 @@ __always_inline bool free_pages_prepare(struct page *page, > > page_cpupid_reset_last(page); > page->flags.f &= ~PAGE_FLAGS_CHECK_AT_PREP; > + page->private = 0; > reset_page_owner(page, order); > page_table_check_free(page, order); > pgalloc_tag_sub(page, 1 << order);