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Sun, 08 Mar 2026 20:15:08 -0700 (PDT) MIME-Version: 1.0 From: Zw Tang Date: Mon, 9 Mar 2026 11:14:58 +0800 X-Gm-Features: AaiRm52UI71Zsv1DyyQfuTtqar8_kcar-WvI_WLGIKWrKj10BzZgSbMrapZjPpE Message-ID: Subject: [BUG] WARNING in alloc_slab_obj_exts triggered by __d_alloc To: Vlastimil Babka , Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, cgroups@vger.kernel.org, Johannes Weiner , Alexander Viro , Andreas Dilger Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Stat-Signature: tipp7xyqqb8ggy9gpwj1gqzsijiqqrxu X-Rspamd-Queue-Id: 203AA180006 X-Rspamd-Server: rspam03 X-HE-Tag: 1773026109-713573 X-HE-Meta: U2FsdGVkX1/t3IR3GDmsAff/DZq6Ru+T5OMZZA6D94RKAdiIEbFay51mTYk/BOwDJidnFDOdA3IuV4ra6RJdBC+WUB4RwN6WZTuZndEN+ge1fzsemrV3GtgabBkrvz6lsh+gVSkm16eKz9lbQzvgFuSlbZH43T9f7/2LQbO5XG7rc64dvWIKdB74LDTjSOUKPSrAdI/kQBQu5wYdNcF6N10nvTtOYESmTyFR/zxJXc2GF5E2xQOOzI8yqtzICBIE84jGoE14QVVDd8ihfQJwI0yonk+DCYhqhUN0N47/yojzw7PSyJ4zB5An8zbh0gPhKAIqaZZzx+BO3OdtUFPu9qk/YpTXOIFyb4pf1ry4wZzWjpOz8KYv/mOJGsbGop+cK1GrTwUc/ICP6A6emsLHrDn2BFn4zOgMIf5zlcKWFNubJm0qb907XJzjN8NrcHK+g+F4aqy5cjyAAJpaqeeHDuMF5nxE+RnpU0GOIxM0uE6kSfLW0HJC6M/3zlIz99AQZPXvzcq6ls6YXq+wM/ytJp/wKYKQ/ASVtKP7JkasGJbCiwjzkMT8U2p1NSppcOqoDzw92R/vBvXEd0ts9PtCMy71Kac58KUA5D2p2wnZHf3bK/feLKoybg0pbnvnKpN3zqXYUP8j/7Hr2Z7034RVmA4ATG2tM0JYNxfj7082qzZWBRw4+MiOtObawqL+zeNByPCdotlmUeL28ahOrxFkKpGp/RAV1uB2SyEYEjPGuojOEm9DPIDudoKlNSeF9MxwiPugX6Uku2608KEuQpoy1EMCl9cNPEv/nq5fbAyMGjZOjCAWl8o417jC4hB/i3ojNeDF9dUyxKLUux83oJa9qLqFHkICNX85V+4ufCOrn4R2esFOdVv/jIRtt2A57KNZA73gu+NmVsNAAMbvyUTGyMm7tqiZfUHy7/h1w8slGEwFpcfYqxAa+ZYmkocUFVAELNqgJBSvneJyNo0D2h9 IuDhUC/U Ym0lus9TgcAGh3X+oyajcSVqQwOUNQxa7tb601Sru1ihnQjgzpa+uD/yPR8gTTU3nnW+hieqF79qJFBuKphmQ2xWy4mTvVBL/Izul5zKZJiz0jrWx5lX2TNvgvqUTxzRwkzBxT5KyjGWutfgKeBcZnmPHrQRcyXnlStKmqCVQildG3zJys0YNQnkiHs/V0Txh1DmZYXG99s+hKSHqAUmPwTsup5vRLkXxN8vJRHNlMv+5Qf0WJLLaSJUsF5SMj5vyKUYSOQHkHP7RNqPgo8ZhJS0Gkq/Dhig0Fu4P3gOIvLWs5OaZUm++Pmf2iay7Ye9fjVYP63pDkdT8ftdrf9aiFOBmWK90tOWrob9PTd6VQ946bPgDj4h+M763loYmmjRfoY2kvzBCIiMv0HWIR+FGd18wnh3LWAEUtJ6P6ZgFjqFR+eegPcgP8GYThwNLCg8owxhc1eyd+s4n6Zo4Y5OCvSuBpg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi, I encountered a WARNING in alloc_slab_obj_exts() while running a syzkaller-generated reproducer on Linux 7.0-rc2. The warning is triggered during dentry allocation (__d_alloc) after mounting a crafted ext4 filesystem image. Kernel git tree: torvalds/linux commit=EF=BC=9A 0031c06807cfa8aa51a759ff8aa09e1aa48149af kernel version:Linux 7.0.0-rc2-00057-g0031c06807cf hardware: QEMU Ubuntu 24.10 I was able to reproduce this issue reliably using the attached reproducer. Reproducer=EF=BC=9A C reproducer: https://pastebin.com/raw/eHjm2Aw6 console output: https://pastebin.com/raw/FQAhquTy kernel config: pastebin.com/raw/CnHdTQNm The warning originates from: mm/slub.c:2189 Call trace: WARNING: mm/slub.c:2189 at alloc_slab_obj_exts+0x132/0x180 CPU: 0 UID: 0 PID: 699 Comm: syz.0.118 Call Trace: __memcg_slab_post_alloc_hook+0x130/0x460 mm/memcontrol.c:3234 memcg_slab_post_alloc_hook mm/slub.c:2464 [inline] slab_post_alloc_hook.constprop.0+0x9c/0xf0 mm/slub.c:4526 slab_alloc_node.constprop.0+0xaa/0x160 mm/slub.c:4844 __do_kmalloc_node mm/slub.c:5237 [inline] __kmalloc_noprof+0x82/0x200 mm/slub.c:5250 kmalloc_noprof include/linux/slab.h:954 [inline] __d_alloc+0x235/0x2f0 fs/dcache.c:1757 d_alloc_pseudo+0x1d/0x70 fs/dcache.c:1871 alloc_path_pseudo fs/file_table.c:364 [inline] alloc_file_pseudo+0x64/0x140 fs/file_table.c:380 __shmem_file_setup+0x136/0x270 mm/shmem.c:5863 memfd_alloc_file+0x81/0x240 mm/memfd.c:471 __do_sys_memfd_create mm/memfd.c:522 [inline] __se_sys_memfd_create mm/memfd.c:505 [inline] __x64_sys_memfd_create+0x205/0x440 mm/memfd.c:505 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x11d/0x5a0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x4b/0x53 The issue happens after mounting an ext4 filesystem image via a loop device created from a compressed image in the reproducer. Relevant kernel messages: EXT4-fs (loop0): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. EXT4-fs (loop3): Delayed block allocation failed for inode 18 at logical offset 768 with max blocks 2 with error 28 EXT4-fs (loop3): This should not happen!! Data will be lost The WARNING occurs in alloc_slab_obj_exts(), which is related to slab object extension allocation. This may indicate a slab metadata inconsistency triggered by the filesystem state. Please let me know if additional debugging information would help. Thanks. Zw Tang