Subject: [syzbot] [net?] KASAN: invalid-free in inet_sock_destruct

From: syzbot <[email-masked]>
Date: Mon, 08 Dec 2025 05:22:26 -0800

Hello,

syzbot found the following issue on:

HEAD commit:    a0c3aefb08cd Merge branch '40GbE' of git://git.kernel.org/..
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=104c5a58580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=3c2e630e5d8a0109
dashboard link: https://syzkaller.appspot.com/bug?extid=ec33a1a006ed5abe7309
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=153eb412580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12fc317c580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/0cc70b728a24/disk-a0c3aefb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/566c56cd7834/vmlinux-a0c3aefb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a0c05f9d1386/bzImage-a0c3aefb.xz

Bisection is inconclusive: the first bad commit could be any of:

151b98d10ef7 net: Add sk_clone().
16942cf4d3e3 sctp: Use sk_clone() in sctp_accept().

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=134067cd980000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

==================================================================
BUG: KASAN: double-free in inet_sock_destruct+0x538/0x740 net/ipv4/af_inet.c:159
Free of addr ffff88801f3430c0 by task ksoftirqd/1/23

CPU: 1 UID: 0 PID: 23 Comm: ksoftirqd/1 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xca/0x240 mm/kasan/report.c:482
 kasan_report_invalid_free+0xea/0x110 mm/kasan/report.c:557
 check_slab_allocation+0xe1/0x130 include/linux/page-flags.h:-1
 kasan_slab_pre_free include/linux/kasan.h:198 [inline]
 slab_free_hook mm/slub.c:2484 [inline]
 slab_free mm/slub.c:6630 [inline]
 kfree+0x148/0x6d0 mm/slub.c:6837
 inet_sock_destruct+0x538/0x740 net/ipv4/af_inet.c:159
 __sk_destruct+0x89/0x660 net/core/sock.c:2350
 sock_put include/net/sock.h:1991 [inline]
 sctp_endpoint_destroy_rcu+0xa1/0xf0 net/sctp/endpointola.c:197
 rcu_do_batch kernel/rcu/tree.c:2605 [inline]
 rcu_core+0xcab/0x1770 kernel/rcu/tree.c:2861
 handle_softirqs+0x286/0x870 kernel/softirq.c:622
 run_ksoftirqd+0x9b/0x100 kernel/softirq.c:1063
 smpboot_thread_fn+0x542/0xa60 kernel/smpboot.c:160
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 6015:
 kasan_save_stack mm/kasan/common.c:56 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
 poison_kmalloc_redzone mm/kasan/common.c:400 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:417
 kasan_kmalloc include/linux/kasan.h:262 [inline]
 __do_kmalloc_node mm/slub.c:5642 [inline]
 __kmalloc_noprof+0x411/0x7f0 mm/slub.c:5654
 kmalloc_noprof include/linux/slab.h:961 [inline]
 kzalloc_noprof include/linux/slab.h:1094 [inline]
 ip_options_get+0x51/0x4c0 net/ipv4/ip_options.c:517
 do_ip_setsockopt+0x1d9b/0x2d00 net/ipv4/ip_sockglue.c:1087
 ip_setsockopt+0x66/0x110 net/ipv4/ip_sockglue.c:1417
 do_sock_setsockopt+0x17c/0x1b0 net/socket.c:2360
 __sys_setsockopt net/socket.c:2385 [inline]
 __do_sys_setsockopt net/socket.c:2391 [inline]
 __se_sys_setsockopt net/socket.c:2388 [inline]
 __x64_sys_setsockopt+0x13f/0x1b0 net/socket.c:2388
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 23:
 kasan_save_stack mm/kasan/common.c:56 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
 __kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:587
 kasan_save_free_info mm/kasan/kasan.h:406 [inline]
 poison_slab_object mm/kasan/common.c:252 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:284
 kasan_slab_free include/linux/kasan.h:234 [inline]
 slab_free_hook mm/slub.c:2539 [inline]
 slab_free mm/slub.c:6630 [inline]
 kfree+0x19a/0x6d0 mm/slub.c:6837
 inet_sock_destruct+0x538/0x740 net/ipv4/af_inet.c:159
 __sk_destruct+0x89/0x660 net/core/sock.c:2350
 sock_put include/net/sock.h:1991 [inline]
 sctp_endpoint_destroy_rcu+0xa1/0xf0 net/sctp/endpointola.c:197
 rcu_do_batch kernel/rcu/tree.c:2605 [inline]
 rcu_core+0xcab/0x1770 kernel/rcu/tree.c:2861
 handle_softirqs+0x286/0x870 kernel/softirq.c:622
 run_ksoftirqd+0x9b/0x100 kernel/softirq.c:1063
 smpboot_thread_fn+0x542/0xa60 kernel/smpboot.c:160
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

The buggy address belongs to the object at ffff88801f3430c0
 which belongs to the cache kmalloc-32 of size 32
The buggy address is located 0 bytes inside of
 32-byte region [ffff88801f3430c0, ffff88801f3430e0)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1f343
anon flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000000 ffff88801a026780 0000000000000000 dead000000000001
raw: 0000000000000000 0000000000400040 00000000f5000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x52800(GFP_NOWAIT|__GFP_NORETRY|__GFP_COMP), pid 184, tgid 184 (kworker/u8:6), ts 6625749703, free_ts 6600992626
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1850
 prep_new_page mm/page_alloc.c:1858 [inline]
 get_page_from_freelist+0x2365/0x2440 mm/page_alloc.c:3884
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5183
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2416
 alloc_slab_page mm/slub.c:3055 [inline]
 allocate_slab+0x96/0x350 mm/slub.c:3228
 new_slab mm/slub.c:3282 [inline]
 ___slab_alloc+0xe94/0x18a0 mm/slub.c:4651
 __slab_alloc+0x65/0x100 mm/slub.c:4770
 __slab_alloc_node mm/slub.c:4846 [inline]
 slab_alloc_node mm/slub.c:5268 [inline]
 __kmalloc_cache_noprof+0x411/0x6f0 mm/slub.c:5758
 kmalloc_noprof include/linux/slab.h:957 [inline]
 slab_free_hook mm/slub.c:2491 [inline]
 slab_free mm/slub.c:6630 [inline]
 kmem_cache_free+0x16f/0x690 mm/slub.c:6740
 __fput_deferred+0x227/0x390 fs/file_table.c:523
 fput_close+0x119/0x200 fs/file_table.c:585
 path_openat+0x313c/0x3830 fs/namei.c:4143
 do_filp_open+0x1fa/0x410 fs/namei.c:4161
 do_open_execat+0x135/0x560 fs/exec.c:783
 alloc_bprm+0x28/0x5c0 fs/exec.c:1410
 kernel_execve+0x9b/0x9f0 fs/exec.c:1885
page last free pid 10 tgid 10 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1394 [inline]
 __free_frozen_pages+0xbc4/0xd30 mm/page_alloc.c:2906
 vfree+0x25a/0x400 mm/vmalloc.c:3440
 delayed_vfree_work+0x55/0x80 mm/vmalloc.c:3359
 process_one_work kernel/workqueue.c:3263 [inline]
 process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3346
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Memory state around the buggy address:
 ffff88801f342f80: 00 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc
 ffff88801f343000: 00 00 00 fc fc fc fc fc 00 00 00 fc fc fc fc fc
>ffff88801f343080: fa fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc
                                           ^
 ffff88801f343100: fa fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc
 ffff88801f343180: fa fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc
==================================================================

---
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