KASAN: slab-use-after-free Read in napi_gro_frags (2)

Status: fixed on 2025/10/29 21:02
Subsystems: net
[Documentation on labels]
Reported-by: syzbot+64e24275ad95a915a313@syzkaller.appspotmail.com
Fix commit: 1091860a16a8 net: tun: Update napi->skb after XDP process
First crash: 345d, last: 329d
Cause bisection: introduced by (bisect log) :
commit e6d5dbdd20aa6a86974af51deb9414cd2e7794cb
Author: Lorenzo Bianconi <lorenzo@kernel.org>
Date: Mon Feb 12 09:50:56 2024 +0000

  xdp: add multi-buff support for xdp running in generic mode

Crash: KASAN: slab-use-after-free Read in napi_gro_frags (log)
Repro: C syz .config
  
▶ ▼ Discussions (2)
Title Replies (including bot) Last reply
[PATCH net] net: tun: Update napi->skb after XDP process 4 (4) 2025/09/19 14:46
[syzbot] [net?] KASAN: slab-use-after-free Read in napi_gro_frags (2) 2 (5) 2025/09/17 02:46
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-use-after-free Read in napi_gro_frags net 19 1 404d 404d 0/29 closed as invalid on 2025/07/30 20:31
▶ ▼ Last patch testing requests (2)
Created Duration User Patch Repo Result
2025/09/17 02:43 2m wangliang74@huawei.com patch net-next error
2025/09/17 01:57 0m wangliang74@huawei.com patch net-next error

Sample crash report:
syz.0.17 uses obsolete (PF_INET,SOCK_PACKET)
==================================================================
BUG: KASAN: slab-use-after-free in skb_reset_mac_header include/linux/skbuff.h:3150 [inline]
BUG: KASAN: slab-use-after-free in napi_frags_skb net/core/gro.c:723 [inline]
BUG: KASAN: slab-use-after-free in napi_gro_frags+0x6e/0x1030 net/core/gro.c:758
Read of size 8 at addr ffff88802ef22c18 by task syz.0.17/6079

CPU: 0 UID: 0 PID: 6079 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
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+0x118/0x150 mm/kasan/report.c:595
 skb_reset_mac_header include/linux/skbuff.h:3150 [inline]
 napi_frags_skb net/core/gro.c:723 [inline]
 napi_gro_frags+0x6e/0x1030 net/core/gro.c:758
 tun_get_user+0x28cb/0x3e20 drivers/net/tun.c:1920
 tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1996
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x5c9/0xb30 fs/read_write.c:686
 ksys_write+0x145/0x250 fs/read_write.c:738
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2f9b98ebe9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fffe90190e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f2f9bbc5fa0 RCX: 00007f2f9b98ebe9
RDX: 000000000000004b RSI: 0000200000000340 RDI: 0000000000000003
RBP: 00007f2f9ba11e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2f9bbc5fa0 R14: 00007f2f9bbc5fa0 R15: 0000000000000003
 </TASK>

Allocated by task 6079:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
 unpoison_slab_object mm/kasan/common.c:330 [inline]
 __kasan_mempool_unpoison_object+0xa0/0x170 mm/kasan/common.c:558
 kasan_mempool_unpoison_object include/linux/kasan.h:388 [inline]
 napi_skb_cache_get+0x37b/0x6d0 net/core/skbuff.c:295
 __alloc_skb+0x11e/0x2d0 net/core/skbuff.c:657
 napi_alloc_skb+0x84/0x7d0 net/core/skbuff.c:811
 napi_get_frags+0x69/0x140 net/core/gro.c:673
 tun_napi_alloc_frags drivers/net/tun.c:1404 [inline]
 tun_get_user+0x77c/0x3e20 drivers/net/tun.c:1784
 tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1996
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x5c9/0xb30 fs/read_write.c:686
 ksys_write+0x145/0x250 fs/read_write.c:738
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 6079:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:576
 poison_slab_object mm/kasan/common.c:243 [inline]
 __kasan_slab_free+0x5b/0x80 mm/kasan/common.c:275
 kasan_slab_free include/linux/kasan.h:233 [inline]
 slab_free_hook mm/slub.c:2422 [inline]
 slab_free mm/slub.c:4695 [inline]
 kmem_cache_free+0x18f/0x400 mm/slub.c:4797
 skb_pp_cow_data+0xdd8/0x13e0 net/core/skbuff.c:969
 netif_skb_check_for_xdp net/core/dev.c:5390 [inline]
 netif_receive_generic_xdp net/core/dev.c:5431 [inline]
 do_xdp_generic+0x699/0x11a0 net/core/dev.c:5499
 tun_get_user+0x2523/0x3e20 drivers/net/tun.c:1872
 tun_chr_write_iter+0x113/0x200 drivers/net/tun.c:1996
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x5c9/0xb30 fs/read_write.c:686
 ksys_write+0x145/0x250 fs/read_write.c:738
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88802ef22b40
 which belongs to the cache skbuff_head_cache of size 240
The buggy address is located 216 bytes inside of
 freed 240-byte region [ffff88802ef22b40, ffff88802ef22c30)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2ef22
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000000 ffff88801e29ca00 ffffea0000a31b80 dead000000000004
raw: 0000000000000000 00000000000c000c 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 0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 1, tgid 1 (swapper/0), ts 19816261324, free_ts 18915708978
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x240/0x2a0 mm/page_alloc.c:1851
 prep_new_page mm/page_alloc.c:1859 [inline]
 get_page_from_freelist+0x21e4/0x22c0 mm/page_alloc.c:3858
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5148
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2416
 alloc_slab_page mm/slub.c:2492 [inline]
 allocate_slab+0x8a/0x370 mm/slub.c:2660
 new_slab mm/slub.c:2714 [inline]
 ___slab_alloc+0xbeb/0x1420 mm/slub.c:3901
 __slab_alloc mm/slub.c:3992 [inline]
 __slab_alloc_node mm/slub.c:4067 [inline]
 slab_alloc_node mm/slub.c:4228 [inline]
 kmem_cache_alloc_node_noprof+0x280/0x3c0 mm/slub.c:4292
 __alloc_skb+0x112/0x2d0 net/core/skbuff.c:659
 alloc_skb include/linux/skbuff.h:1377 [inline]
 nlmsg_new include/net/netlink.h:1055 [inline]
 rtmsg_ifinfo_build_skb+0x84/0x260 net/core/rtnetlink.c:4392
 rtmsg_ifinfo_event net/core/rtnetlink.c:4434 [inline]
 rtmsg_ifinfo+0x8c/0x1a0 net/core/rtnetlink.c:4443
 register_netdevice+0x1712/0x1ae0 net/core/dev.c:11307
 register_netdev+0x40/0x60 net/core/dev.c:11371
 nr_proto_init+0x145/0x710 net/netrom/af_netrom.c:1424
 do_one_initcall+0x233/0x820 init/main.c:1269
 do_initcall_level+0x104/0x190 init/main.c:1331
 do_initcalls+0x59/0xa0 init/main.c:1347
page last free pid 920 tgid 920 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1395 [inline]
 __free_frozen_pages+0xbc4/0xd30 mm/page_alloc.c:2895
 vfree+0x25a/0x400 mm/vmalloc.c:3434
 delayed_vfree_work+0x55/0x80 mm/vmalloc.c:3353
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3319
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400
 kthread+0x70e/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Memory state around the buggy address:
 ffff88802ef22b00: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
 ffff88802ef22b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88802ef22c00: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
                            ^
 ffff88802ef22c80: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88802ef22d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc
==================================================================

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/09/09 04:02 net-next f3883b1ea5a8 d291dd2d .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce KASAN: slab-use-after-free Read in napi_gro_frags
2025/08/24 12:48 upstream 8d245acc1e88 bf27483f .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 KASAN: slab-use-after-free Read in napi_gro_frags
2025/09/09 02:56 net-next f3883b1ea5a8 d291dd2d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce KASAN: slab-use-after-free Read in napi_gro_frags
* Struck through repros no longer work on HEAD.