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Sun, 08 Nov 2026 19:58:37 -0800 (PST) Date: Sun, 08 Nov 2026 19:58:37 -0800 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6af144ed.f50b2b3a.2c0de7.0010.GAE@google.com> Subject: [syzbot] [mm?] [bluetooth?] BUG: unable to handle kernel NULL pointer dereference in __refill_objects_node From: syzbot To: akpm@linux-foundation.org, bsegall@google.com, david@kernel.org, dietmar.eggemann@arm.com, juri.lelli@redhat.com, kees@kernel.org, kprateek.nayak@amd.com, liam@infradead.org, linux-bluetooth@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, ljs@kernel.org, luiz.dentz@gmail.com, marcel@holtmann.org, mgorman@suse.de, mhocko@suse.com, mingo@redhat.com, peterz@infradead.org, rostedt@goodmis.org, rppt@kernel.org, surenb@google.com, syzkaller-bugs@googlegroups.com, vbabka@kernel.org, vincent.guittot@linaro.org, vschneid@redhat.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: 58c1eb84e977 arm64: sdei: Preserve the interrupted context.. git tree: git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci console output: https://syzkaller.appspot.com/x/log.txt?x=12d1d369580000 kernel config: https://syzkaller.appspot.com/x/.config?x=a58b6b4d667e7a61 dashboard link: https://syzkaller.appspot.com/bug?extid=73e34786d639a8eb1324 compiler: Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8 userspace arch: arm64 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1255c1a1580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/b1ec47537e12/disk-58c1eb84.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/3bca0c2b1169/vmlinux-58c1eb84.xz kernel image: https://storage.googleapis.com/syzbot-assets/0a7c49594d5a/Image-58c1eb84.gz.xz AI-generated root cause summary: In mm/slub.c, __refill_objects_node() replenishes percpu sheaves by detaching a freelist from a partial slab via get_freelist_nofreeze() and iterating through the freelist pointers in a while (count && refilled < max) loop. Because the loop condition only checks count and refilled rather than validating that object is non-NULL, a prematurely terminated or corrupted freelist (where fewer objects are linked in slab->freelist than the expected count = slab->objects - slab->inuse) causes object to become NULL before count reaches zero. On the subsequent iteration, get_freepointer() dereferences NULL + s->offset (offset 0x400 for kmalloc-2k), resulting in an immediate kernel NULL pointer dereference crash at address 0x0000000000000400. full analysis: https://syzkaller.appspot.com/x/ai_root_cause?x=73e34786d639a8eb1324 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+73e34786d639a8eb1324@syzkaller.appspotmail.com Unable to handle kernel NULL pointer dereference at virtual address 00000000000004e8 Mem abort info: ESR = 0x0000000096000005 EC = 0x25: DABT (current EL), IL = 32 bits SET = 0, FnV = 0 EA = 0, S1PTW = 0 FSC = 0x05: level 1 translation fault Data abort info: ISV = 0, ISS = 0x00000005, ISS2 = 0x00000000 CM = 0, WnR = 0, TnD = 0, TagAccess = 0 GCS = 0, Overlay = 0, DirtyBit = 0 user pgtable: 4k pages, 48-bit VAs, pgdp=000000011857f000 [00000000000004e8] pgd=080000011cba0403, p4d=080000011cba0403, pud=0000000000000000 Internal error: Oops: 0000000096000005 [#1] SMP Modules linked in: CPU: 0 UID: 0 PID: 4870 Comm: syz-executor Not tainted syzkaller #0 PREEMPT Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/06/2026 pstate: 83400005 (Nzcv daif +PAN -UAO +TCO +DIT -SSBS BTYPE=--) pc : get_freepointer mm/slub.c:596 [inline] pc : __refill_objects_node+0x308/0x510 mm/slub.c:7413 lr : get_freelist_nofreeze mm/slub.c:4494 [inline] lr : __refill_objects_node+0x2b8/0x510 mm/slub.c:7409 sp : ffff800094587600 x29: ffff800094587690 x28: 0000000000000000 x27: 0000000000000000 x26: 0000000000000006 x25: fffffdffc3256e00 x24: 0000000000000003 x23: 0000000000000006 x22: 000000000000000c x21: 0000000000000001 x20: ffff0000c0022138 x19: 0000000000000004 x18: ffff800123625000 x17: ffff0001ace953a6 x16: ffff0000db9cd894 x15: 00000000000c8000 x14: 00000000005c615b x13: 0000000000000001 x12: 0000000000000003 x11: 0000000000000000 x10: fffffdffc3256e20 x9 : ffff0000c0022120 x8 : 00000000000004e8 x7 : 0000000000000000 x6 : 0000000000000000 x5 : 0000000000000001 x4 : 0000000000000008 x3 : 00000002000c000c x2 : 0000000000000000 x1 : 00000002000c0003 x0 : 0000000000000001 Call trace: get_freepointer mm/slub.c:595 [inline] (P) __refill_objects_node+0x308/0x510 mm/slub.c:7413 (P) refill_objects+0x78/0x320 mm/slub.c:7526 refill_sheaf+0x44/0x6c mm/slub.c:2917 __pcs_replace_empty_main+0x22c/0x4f4 mm/slub.c:4811 alloc_from_pcs mm/slub.c:4887 [inline] slab_alloc_node mm/slub.c:5021 [inline] kmem_cache_alloc_noprof+0x35c/0x5d4 mm/slub.c:5047 dup_mm kernel/fork.c:1532 [inline] copy_mm+0xb8/0x328 kernel/fork.c:1594 copy_process+0x1698/0x35a0 kernel/fork.c:2320 kernel_clone+0x234/0x8e8 kernel/fork.c:2790 __do_sys_clone kernel/fork.c:2932 [inline] __se_sys_clone kernel/fork.c:2900 [inline] __arm64_sys_clone+0x168/0x1d4 kernel/fork.c:2900 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x244 arch/arm64/kernel/syscall.c:49 el0_svc_common+0xec/0x23c arch/arm64/kernel/syscall.c:121 do_el0_svc+0x4c/0x5c arch/arm64/kernel/syscall.c:140 el0_svc+0x60/0x1d8 arch/arm64/kernel/entry-common.c:797 el0t_64_sync_handler+0x44/0x104 arch/arm64/kernel/entry-common.c:816 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:606 Code: f9401fe8 f900029b 2a1a03f7 b9402908 (f87b691c) ---[ end trace 0000000000000000 ]--- ---------------- Code disassembly (best guess): 0: f9401fe8 ldr x8, [sp, #56] 4: f900029b str x27, [x20] 8: 2a1a03f7 mov w23, w26 c: b9402908 ldr w8, [x8, #40] * 10: f87b691c ldr x28, [x8, x27] <-- trapping instruction --- This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@googlegroups.com. syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. If the report is already addressed, let syzbot know by replying with: #syz fix: exact-commit-title If you want syzbot to run the reproducer, reply with: #syz test: git://repo/address.git branch-or-commit-hash If you attach or paste a git patch, syzbot will apply it before testing. If you want to overwrite report's subsystems, reply with: #syz set subsystems: new-subsystem (See the list of subsystem names on the web dashboard) If the report is a duplicate of another one, reply with: #syz dup: exact-subject-of-another-report If you want to undo deduplication, reply with: #syz undup