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Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] mm/huge_memory: fix folio split check for anon folios in swapcache. 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?WO7PzOdzJRY/1pAaue6+Q++RCeUu7bDteuZaHwc66wzBeXYA+iptfTi0k2x3?= =?us-ascii?Q?Dh+VQITldulH0r4O+Fd9jNXjX42E9EAWJb0nl4RFHtsO+13Ytu//2vunGw2g?= =?us-ascii?Q?l8oLmdYA3vXB5METYnY7yXNvApuGqttEo9UnEN2JlA4np8OLmHjMh+bs66Ht?= =?us-ascii?Q?SxY54/F12+5cgpmKYh8Pxmd/KaaBShQ9wXw7HKbbRilwGVrPJKDXTVJtx5ok?= =?us-ascii?Q?ciujvOLxpywEC8ONCSl0Fq2Qosw5CA3D5F1T51yir/S2sIL5FEyJmVmD21L8?= =?us-ascii?Q?fHnxmWgQjb0jb8MrrwcnHYypRq2U5xN02MDWzhlGbGQAtI9LO0bLeHxzPlVi?= =?us-ascii?Q?YMrQjXVHO9WK6sjcBRByfsiF9dNYmKswR6xyWNgXQJxGH7dteRp3TZ00K12u?= =?us-ascii?Q?5nNkpOnWMqrRnSnHD6+/F8rrj8IEUeRsyfM4vFN8xrqnAK7byauV/m4QwruE?= =?us-ascii?Q?t/hIT06R4WG7aR2/IBo0ST/aa/E8W7t0L9OqH8Y7XtASbW0riYgpniod2sk9?= =?us-ascii?Q?ex4fc8G+EBJyTyh7HzS91l3W8Oo8NCtNtRaTBm2CxhAzi+O2EArmJtUDc5cG?= =?us-ascii?Q?W4Rjt/ojcz9mRsEgVfQp4bokvSpXR5QwRoNdgNdUVk3VmzdNBIPFhdX5m+Y4?= =?us-ascii?Q?LMLpH7sr0k+uPnEPMAEgb8eaOKilRl1yCsTvqYsZ0EboEp2DJOCAOa8P9ktR?= =?us-ascii?Q?MMJE/pm/5Bt3TDbO/XagQlq7Hs0TWJeqKjWdc4w+WzP1DvV5Z8BNU7HePl/m?= =?us-ascii?Q?ISYVFlABNMKKQ3JXYbTDMuU8QcSzb8v5XsX9lK0sw57b2jQdjBuyMvvEIxfQ?= =?us-ascii?Q?FBSraKwcJk/9YVtKB3IEP5+Tlc4xSNUGVVxQp+eHfoXynxw1Kd6BYwWWhJtT?= =?us-ascii?Q?oJWOrUFrGIx7jzYfA5Hn9/5lGVd0S/v3JNGAbRCpVkkjCYc/PixBgQDjIcuh?= =?us-ascii?Q?syRnUQujCGty8VJodiPcqminHv5A62xX1LY+ZmyMjfH1BH44bOcaeGg6MIu3?= =?us-ascii?Q?rV3+y2dQ3iJxI/lT1wGMlPKay4tQ7jc6psktUvBX3S2icvj3DQZHq96zIJ6d?= =?us-ascii?Q?3bdFDlGgn0PAKKojrqa2LPfH93uIMVCE+tt1anR4NxLLTp8V3O5n754AS7VG?= =?us-ascii?Q?dWH7ZTQaur5NXmr1urKLktiCqzwj5QPNRNSjbjb8YGcTLjgmalo+K7xBvGNv?= =?us-ascii?Q?HovcZaEobJGLhUi11u0jxOCHSfY+FEPz0aLOPK7NRII+TPG5rFBcGDo2zhBq?= =?us-ascii?Q?S9I4HQNIGQIqyEC742aTp+jib1cekU6Cpj3BHjYFgpR/L2gD2NQqKQ3se3v+?= =?us-ascii?Q?uLI8DWb2poFHEHKnnq3SFclD2n9uFDz6A/oKRQSS9GLyH00ghZi1Ij0mxzeX?= =?us-ascii?Q?Ay59QQ1guBgV0jY4msdKNX3lC+qoWJPQwRGglHkcirReznSthBx3ZaTghlH6?= =?us-ascii?Q?12g12qK4RuOnvQyOSOhWpBicLMXZFjB8+Cjy91jjFscmTtC6J65/jmJsWrKV?= =?us-ascii?Q?Xd8X3whclwZ7LAj45ujsdLZ//+3rzxPknTfpBOwlmqAQdDfoIfTnbOkqwBRw?= =?us-ascii?Q?wDL7Gynb8F1g3vNCI3sNcNTeQYbyEehO9kWvud0r?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 31337e21-7d59-40ae-81fd-08de1cca3327 X-MS-Exchange-CrossTenant-AuthSource: DS7PR12MB9473.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Nov 2025 00:19:50.2007 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: UdKiqi+dLmKmWvj386aYxGzBFlZfm7O1x3mjf9CW4EMH13pWbff6efhKSWbt65Y6 X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS0PR12MB8443 On 5 Nov 2025, at 18:57, Andrew Morton wrote: > On Wed, 5 Nov 2025 11:29:10 -0500 Zi Yan wrote: > >> Both uniform and non uniform split check missed the check to prevent >> splitting anon folios in swapcache to non-zero order. Fix the check. > > Please describe the possible userspace-visible effects of the bug > especially when proposing a -stable backport. Splitting anon folios in swapcache to non-zero order can cause data corruption since swapcache only support PMD order and order-0 entries. This can happen when one use split_huge_pages under debugfs to split anon folios in swapcache. > >> Fixes: 58729c04cf10 ("mm/huge_memory: add buddy allocator like (non-un= iform) folio_split()") >> Reported-by: "David Hildenbrand (Red Hat)" >> Closes: https://lore.kernel.org/all/dc0ecc2c-4089-484f-917f-920fdca4c8= 98@kernel.org/ > > I was hopeful, but that's "from code inspection". In-tree callers do not perform such an illegal operation. Only debugfs interface could trigger it. I will put adding a test case on my TODO list. > >> Cc: stable@vger.kernel.org >> Signed-off-by: Zi Yan Best Regards, Yan, Zi