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In-Reply-To: <20260225185121.2057388-1-memxor@gmail.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <69a01309.050a0220.2fcbed.0007.GAE@google.com> Subject: [syzbot ci] Re: Close race in freeing special fields and map value From: syzbot ci To: andrii@kernel.org, ast@kernel.org, bpf@vger.kernel.org, daniel@iogearbox.net, eddyz87@gmail.com, kernel-team@meta.com, kkd@meta.com, martin.lau@kernel.org, memxor@gmail.com, paulmck@kernel.org, yatsenko@meta.com Cc: syzbot@lists.linux.dev, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" syzbot ci has tested the following series [v1] Close race in freeing special fields and map value https://lore.kernel.org/all/20260225185121.2057388-1-memxor@gmail.com * [PATCH bpf-next v1 1/4] bpf: Register dtor for freeing special fields * [PATCH bpf-next v1 2/4] bpf: Delay freeing fields in local storage * [PATCH bpf-next v1 3/4] bpf: Retire rcu_trace_implies_rcu_gp() from local storage * [PATCH bpf-next v1 4/4] selftests/bpf: Add tests for special fields races and found the following issue: KASAN: slab-use-after-free Read in free_all Full report is available here: https://ci.syzbot.org/series/ad9c7ce6-d861-4afe-821a-e8fae6120b12 *** KASAN: slab-use-after-free Read in free_all tree: bpf-next URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/bpf/bpf-next.git base: f620af11c27b8ec9994a39fe968aa778112d1566 arch: amd64 compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8 config: https://ci.syzbot.org/builds/b2735b0b-963d-41a7-bb33-db10494a24e1/config syz repro: https://ci.syzbot.org/findings/3ee61f99-7d80-4986-a0b1-492ffb6b1c46/syz_repro ================================================================== BUG: KASAN: slab-use-after-free in free_all+0x84/0x140 kernel/bpf/memalloc.c:271 Read of size 8 at addr ffff888112ee9260 by task swapper/0/0 CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0xba/0x230 mm/kasan/report.c:482 kasan_report+0x117/0x150 mm/kasan/report.c:595 free_all+0x84/0x140 kernel/bpf/memalloc.c:271 do_call_rcu_ttrace+0x385/0x400 kernel/bpf/memalloc.c:315 __free_by_rcu+0x23b/0x3f0 kernel/bpf/memalloc.c:381 rcu_do_batch kernel/rcu/tree.c:2617 [inline] rcu_core+0x7cd/0x1070 kernel/rcu/tree.c:2869 handle_softirqs+0x22a/0x870 kernel/softirq.c:622 __do_softirq kernel/softirq.c:656 [inline] invoke_softirq kernel/softirq.c:496 [inline] __irq_exit_rcu+0x5f/0x150 kernel/softirq.c:723 irq_exit_rcu+0x9/0x30 kernel/softirq.c:739 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1056 [inline] sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1056 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697 RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:63 Code: 8e 6d 02 c3 cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa eb 07 0f 00 2d 43 3d 1c 00 fb f4 7c ea 02 00 cc cc cc cc cc cc cc cc cc cc cc cc 90 90 90 90 90 RSP: 0018:ffffffff8e407dc0 EFLAGS: 00000202 RAX: 00000000000d2297 RBX: ffffffff819a80ad RCX: 0000000080000001 RDX: 0000000000000001 RSI: ffffffff8def22fa RDI: ffffffff8c27a800 RBP: ffffffff8e407eb0 R08: ffff88812103395b R09: 1ffff1102420672b R10: dffffc0000000000 R11: ffffed102420672c R12: ffffffff90117db0 R13: 1ffffffff1c929d8 R14: 0000000000000000 R15: 0000000000000000 arch_safe_halt arch/x86/kernel/process.c:766 [inline] default_idle+0x9/0x20 arch/x86/kernel/process.c:767 default_idle_call+0x72/0xb0 kernel/sched/idle.c:122 cpuidle_idle_call kernel/sched/idle.c:191 [inline] do_idle+0x1bd/0x500 kernel/sched/idle.c:332 cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:430 rest_init+0x2de/0x300 init/main.c:760 start_kernel+0x385/0x3d0 init/main.c:1210 x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310 x86_64_start_kernel+0x143/0x1c0 arch/x86/kernel/head64.c:291 common_startup_64+0x13e/0x147 Allocated by task 5961: kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 poison_kmalloc_redzone mm/kasan/common.c:398 [inline] __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415 kasan_kmalloc include/linux/kasan.h:263 [inline] __do_kmalloc_node mm/slub.c:5219 [inline] __kmalloc_node_noprof+0x4e0/0x7c0 mm/slub.c:5225 kmalloc_node_noprof include/linux/slab.h:1093 [inline] __bpf_map_area_alloc kernel/bpf/syscall.c:398 [inline] bpf_map_area_alloc+0x64/0x170 kernel/bpf/syscall.c:411 trie_alloc+0x14f/0x340 kernel/bpf/lpm_trie.c:588 map_create+0xafd/0x16a0 kernel/bpf/syscall.c:1507 __sys_bpf+0x6e1/0x950 kernel/bpf/syscall.c:6210 __do_sys_bpf kernel/bpf/syscall.c:6341 [inline] __se_sys_bpf kernel/bpf/syscall.c:6339 [inline] __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:6339 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Freed by task 83: kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584 poison_slab_object mm/kasan/common.c:253 [inline] __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285 kasan_slab_free include/linux/kasan.h:235 [inline] slab_free_hook mm/slub.c:2687 [inline] slab_free mm/slub.c:6124 [inline] kfree+0x1c1/0x630 mm/slub.c:6442 bpf_map_free kernel/bpf/syscall.c:892 [inline] bpf_map_free_deferred+0x217/0x460 kernel/bpf/syscall.c:919 process_one_work kernel/workqueue.c:3275 [inline] process_scheduled_works+0xb02/0x1830 kernel/workqueue.c:3358 worker_thread+0xa50/0xfc0 kernel/workqueue.c:3439 kthread+0x388/0x470 kernel/kthread.c:467 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 Last potentially related work creation: kasan_save_stack+0x3e/0x60 mm/kasan/common.c:57 kasan_record_aux_stack+0xbd/0xd0 mm/kasan/generic.c:556 insert_work+0x3d/0x330 kernel/workqueue.c:2199 __queue_work+0xd03/0x1020 kernel/workqueue.c:2354 queue_work_on+0x106/0x1d0 kernel/workqueue.c:2405 bpf_map_put_with_uref kernel/bpf/syscall.c:975 [inline] bpf_map_release+0x127/0x140 kernel/bpf/syscall.c:985 __fput+0x44f/0xa70 fs/file_table.c:469 task_work_run+0x1d9/0x270 kernel/task_work.c:233 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] __exit_to_user_mode_loop kernel/entry/common.c:67 [inline] exit_to_user_mode_loop+0xed/0x480 kernel/entry/common.c:98 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline] syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline] syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline] do_syscall_64+0x32d/0xf80 arch/x86/entry/syscall_64.c:100 entry_SYSCALL_64_after_hwframe+0x77/0x7f The buggy address belongs to the object at ffff888112ee9000 which belongs to the cache kmalloc-cg-1k of size 1024 The buggy address is located 608 bytes inside of freed 1024-byte region [ffff888112ee9000, ffff888112ee9400) The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x112ee8 head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 memcg:ffff888106b17c01 flags: 0x17ff00000000040(head|node=0|zone=2|lastcpupid=0x7ff) page_type: f5(slab) raw: 017ff00000000040 ffff88810005d280 dead000000000100 dead000000000122 raw: 0000000000000000 0000000800100010 00000000f5000000 ffff888106b17c01 head: 017ff00000000040 ffff88810005d280 dead000000000100 dead000000000122 head: 0000000000000000 0000000800100010 00000000f5000000 ffff888106b17c01 head: 017ff00000000003 ffffea00044bba01 00000000ffffffff 00000000ffffffff head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5550, tgid 5550 (dhcpcd), ts 37867090520, free_ts 37834172120 set_page_owner include/linux/page_owner.h:32 [inline] post_alloc_hook+0x231/0x280 mm/page_alloc.c:1889 prep_new_page mm/page_alloc.c:1897 [inline] get_page_from_freelist+0x24dc/0x2580 mm/page_alloc.c:3962 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5250 alloc_slab_page mm/slub.c:3255 [inline] allocate_slab+0x77/0x660 mm/slub.c:3444 new_slab mm/slub.c:3502 [inline] refill_objects+0x331/0x3c0 mm/slub.c:7134 refill_sheaf mm/slub.c:2804 [inline] __pcs_replace_empty_main+0x2b9/0x620 mm/slub.c:4578 alloc_from_pcs mm/slub.c:4681 [inline] slab_alloc_node mm/slub.c:4815 [inline] __do_kmalloc_node mm/slub.c:5218 [inline] __kmalloc_node_track_caller_noprof+0x572/0x7b0 mm/slub.c:5327 kmalloc_reserve net/core/skbuff.c:635 [inline] __alloc_skb+0x2c1/0x7d0 net/core/skbuff.c:713 alloc_skb include/linux/skbuff.h:1383 [inline] alloc_skb_with_frags+0xca/0x890 net/core/skbuff.c:6750 sock_alloc_send_pskb+0x878/0x990 net/core/sock.c:2995 unix_dgram_sendmsg+0x460/0x18e0 net/unix/af_unix.c:2125 sock_sendmsg_nosec net/socket.c:727 [inline] __sock_sendmsg net/socket.c:742 [inline] sock_write_iter+0x503/0x550 net/socket.c:1195 do_iter_readv_writev+0x619/0x8c0 fs/read_write.c:-1 vfs_writev+0x33c/0x990 fs/read_write.c:1059 do_writev+0x154/0x2e0 fs/read_write.c:1105 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 page last free pid 5678 tgid 5678 stack trace: reset_page_owner include/linux/page_owner.h:25 [inline] __free_pages_prepare mm/page_alloc.c:1433 [inline] __free_frozen_pages+0xc2b/0xdb0 mm/page_alloc.c:2978 __slab_free+0x263/0x2b0 mm/slub.c:5532 qlink_free mm/kasan/quarantine.c:163 [inline] qlist_free_all+0x97/0x100 mm/kasan/quarantine.c:179 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:350 kasan_slab_alloc include/linux/kasan.h:253 [inline] slab_post_alloc_hook mm/slub.c:4501 [inline] slab_alloc_node mm/slub.c:4830 [inline] __do_kmalloc_node mm/slub.c:5218 [inline] __kmalloc_noprof+0x316/0x760 mm/slub.c:5231 kmalloc_noprof include/linux/slab.h:966 [inline] tomoyo_realpath_from_path+0xe3/0x5d0 security/tomoyo/realpath.c:251 tomoyo_realpath_nofollow+0xc3/0x110 security/tomoyo/realpath.c:304 tomoyo_find_next_domain+0x259/0x1aa0 security/tomoyo/domain.c:731 tomoyo_bprm_check_security+0x11b/0x180 security/tomoyo/tomoyo.c:102 security_bprm_check+0x85/0x240 security/security.c:794 search_binary_handler fs/exec.c:1654 [inline] exec_binprm fs/exec.c:1696 [inline] bprm_execve+0x896/0x1460 fs/exec.c:1748 do_execveat_common+0x50d/0x690 fs/exec.c:1846 __do_sys_execve fs/exec.c:1930 [inline] __se_sys_execve fs/exec.c:1924 [inline] __x64_sys_execve+0x97/0xc0 fs/exec.c:1924 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Memory state around the buggy address: ffff888112ee9100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888112ee9180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff888112ee9200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff888112ee9280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff888112ee9300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== ---------------- Code disassembly (best guess): 0: 8e 6d 02 mov 0x2(%rbp),%gs 3: c3 ret 4: cc int3 5: cc int3 6: cc int3 7: cc int3 8: cc int3 9: cc int3 a: cc int3 b: 90 nop c: 90 nop d: 90 nop e: 90 nop f: 90 nop 10: 90 nop 11: 90 nop 12: 90 nop 13: 90 nop 14: 90 nop 15: 90 nop 16: 90 nop 17: 90 nop 18: 90 nop 19: 90 nop 1a: 90 nop 1b: f3 0f 1e fa endbr64 1f: eb 07 jmp 0x28 21: 0f 00 2d 43 3d 1c 00 verw 0x1c3d43(%rip) # 0x1c3d6b 28: fb sti 29: f4 hlt * 2a: e9 7c ea 02 00 jmp 0x2eaab <-- trapping instruction 2f: cc int3 30: cc int3 31: cc int3 32: cc int3 33: cc int3 34: cc int3 35: cc int3 36: cc int3 37: cc int3 38: cc int3 39: cc int3 3a: cc int3 3b: 90 nop 3c: 90 nop 3d: 90 nop 3e: 90 nop 3f: 90 nop *** If these findings have caused you to resend the series or submit a separate fix, please add the following tag to your commit message: Tested-by: syzbot@syzkaller.appspotmail.com --- This report is generated by a bot. It may contain errors. syzbot ci engineers can be reached at syzkaller@googlegroups.com.