================================================================== BUG: KASAN: use-after-free in nfsd_svc+0x996/0xab0 fs/nfsd/nfssvc.c:813 Read of size 4 at addr ffff888018654c54 by task syz.1.57/4501 CPU: 0 PID: 4501 Comm: syz.1.57 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 Call Trace: dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106 print_address_description mm/kasan/report.c:316 [inline] print_report+0xa8/0x210 mm/kasan/report.c:420 kasan_report+0x10b/0x140 mm/kasan/report.c:524 nfsd_svc+0x996/0xab0 fs/nfsd/nfssvc.c:813 write_threads+0x2ea/0x350 fs/nfsd/nfsctl.c:424 nfsctl_transaction_write+0x105/0x150 fs/nfsd/nfsctl.c:114 vfs_write+0x2dc/0x9a0 fs/read_write.c:582 ksys_write+0x14d/0x260 fs/read_write.c:637 do_syscall_x64 arch/x86/entry/common.c:46 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76 entry_SYSCALL_64_after_hwframe+0x68/0xd2 RIP: 0033:0x7fa020d9e159 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fa021d31028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007fa021025fa0 RCX: 00007fa020d9e159 RDX: 0000000000000002 RSI: 0000200000000500 RDI: 0000000000000003 RBP: 00007fa020e3503b R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fa021026038 R14: 00007fa021025fa0 R15: 00007fff7537a268 Allocated by task 4501: kasan_save_stack mm/kasan/common.c:46 [inline] kasan_set_track+0x4b/0x70 mm/kasan/common.c:53 ____kasan_kmalloc mm/kasan/common.c:375 [inline] __kasan_kmalloc+0x8e/0xa0 mm/kasan/common.c:384 kmalloc include/linux/slab.h:563 [inline] kzalloc include/linux/slab.h:699 [inline] __svc_create+0x60/0x9d0 net/sunrpc/svc.c:491 svc_create_pooled+0x71f/0x8c0 net/sunrpc/svc.c:579 nfsd_create_serv+0x2f9/0x700 fs/nfsd/nfssvc.c:667 nfsd_svc+0x17f/0xab0 fs/nfsd/nfssvc.c:796 write_threads+0x2ea/0x350 fs/nfsd/nfsctl.c:424 nfsctl_transaction_write+0x105/0x150 fs/nfsd/nfsctl.c:114 vfs_write+0x2dc/0x9a0 fs/read_write.c:582 ksys_write+0x14d/0x260 fs/read_write.c:637 do_syscall_x64 arch/x86/entry/common.c:46 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76 entry_SYSCALL_64_after_hwframe+0x68/0xd2 Freed by task 4501: kasan_save_stack mm/kasan/common.c:46 [inline] kasan_set_track+0x4b/0x70 mm/kasan/common.c:53 kasan_save_free_info+0x27/0x40 mm/kasan/generic.c:516 ____kasan_slab_free+0x126/0x1f0 mm/kasan/common.c:237 kasan_slab_free include/linux/kasan.h:177 [inline] slab_free_hook mm/slub.c:1729 [inline] slab_free_freelist_hook+0x133/0x1b0 mm/slub.c:1755 slab_free mm/slub.c:3687 [inline] __kmem_cache_free+0xb6/0x200 mm/slub.c:3700 kref_put include/linux/kref.h:65 [inline] svc_put include/linux/sunrpc/svc.h:123 [inline] nfsd_svc+0x75e/0xab0 fs/nfsd/nfssvc.c:811 write_threads+0x2ea/0x350 fs/nfsd/nfsctl.c:424 nfsctl_transaction_write+0x105/0x150 fs/nfsd/nfsctl.c:114 vfs_write+0x2dc/0x9a0 fs/read_write.c:582 ksys_write+0x14d/0x260 fs/read_write.c:637 do_syscall_x64 arch/x86/entry/common.c:46 [inline] do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76 entry_SYSCALL_64_after_hwframe+0x68/0xd2 The buggy address belongs to the object at ffff888018654c00 which belongs to the cache kmalloc-512 of size 512 The buggy address is located 84 bytes inside of 512-byte region [ffff888018654c00, ffff888018654e00) The buggy address belongs to the physical page: page:ffffea0000619500 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x18654 head:ffffea0000619500 order:2 compound_mapcount:0 compound_pincount:0 flags: 0xfff00000010200(slab|head|node=0|zone=1|lastcpupid=0x7ff) raw: 00fff00000010200 0000000000000000 dead000000000001 ffff888017441c80 raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 2361201479, free_ts 0 set_page_owner include/linux/page_owner.h:31 [inline] post_alloc_hook+0x173/0x1a0 mm/page_alloc.c:2560 prep_new_page mm/page_alloc.c:2567 [inline] get_page_from_freelist+0x206b/0x2180 mm/page_alloc.c:4358 __alloc_pages+0x1ec/0x4f0 mm/page_alloc.c:5658 alloc_page_interleave+0x24/0x1e0 mm/mempolicy.c:2115 alloc_slab_page+0x5d/0x180 mm/slub.c:1799 allocate_slab mm/slub.c:1944 [inline] new_slab+0x87/0x2d0 mm/slub.c:1997 ___slab_alloc+0xbc5/0x1240 mm/slub.c:3154 __slab_alloc mm/slub.c:3240 [inline] slab_alloc_node mm/slub.c:3325 [inline] __kmem_cache_alloc_node+0x126/0x270 mm/slub.c:3398 __do_kmalloc_node mm/slab_common.c:935 [inline] __kmalloc_node_track_caller+0xa0/0x240 mm/slab_common.c:956 __do_krealloc mm/slab_common.c:1336 [inline] krealloc+0x6a/0x100 mm/slab_common.c:1369 add_sysfs_param+0xe8/0x920 kernel/params.c:645 kernel_add_sysfs_param+0xaf/0x11b kernel/params.c:798 param_sysfs_builtin+0x20d/0x2ae kernel/params.c:837 param_sysfs_init+0x66/0x6a kernel/params.c:958 do_one_initcall+0x257/0x800 init/main.c:1270 do_initcall_level+0x13d/0x1ed init/main.c:1343 page_owner free stack trace missing Memory state around the buggy address: ffff888018654b00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888018654b80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff888018654c00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888018654c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888018654d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ==================================================================