KASAN: use-after-free Read in ipt_do_table (3)

Status: premoderation: reported on 2026/10/10 06:04
Reported-by: syzbot+ddb8fddfe7f1960fada8@syzkaller.appspotmail.com
First crash: 2d02h, last: 2d02h
▶ ▼ Similar bugs (12)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-4.19 KASAN: use-after-free Read in ipt_do_table 19 1 2439d 2439d 0/1 auto-closed as invalid on 2020/06/06 05:50
android-5-10 KASAN: use-after-free Read in ipt_do_table 19 4 266d 315d 0/2 auto-obsoleted due to no activity on 2026/04/19 06:45
android-6-1 KASAN: use-after-free Read in ipt_do_table (2) 19 1 10d 10d 0/2 premoderation: reported on 2026/10/01 15:11
android-5-15 KASAN: use-after-free Read in ipt_do_table 19 1 359d 359d 0/2 auto-obsoleted due to no activity on 2026/01/15 08:55
android-5-15 KASAN: use-after-free Read in ipt_do_table (2) 19 2 124d 134d 0/2 auto-obsoleted due to no activity on 2026/09/08 07:46
upstream KASAN: use-after-free Read in ipt_do_table netfilter 19 syz error error 16 1485d 1633d 0/29 closed as invalid on 2022/11/17 17:58
android-5-10 KASAN: use-after-free Read in ipt_do_table (2) 19 3 149d 166d 0/2 auto-obsoleted due to no activity on 2026/08/13 15:22
android-6-1 KASAN: use-after-free Read in ipt_do_table 19 1 351d 351d 0/2 auto-obsoleted due to no activity on 2026/01/24 06:12
android-5-10 KASAN: use-after-free Read in ipt_do_table (3) 19 3 9d00h 18d 0/2 premoderation: reported on 2026/09/24 00:31
upstream BUG: unable to handle kernel paging request in ipt_do_table netfilter 8 1 1910d 1906d 0/29 auto-closed as invalid on 2021/10/17 23:06
linux-4.19 general protection fault in ipt_do_table 2 1 2017d 2017d 0/1 auto-closed as invalid on 2021/08/01 14:21
upstream KASAN: slab-use-after-free Read in ipt_do_table netfilter 19 1 343d 343d 0/29 closed as invalid on 2026/01/07 12:42

Sample crash report:
EXT4-fs (loop3): shut down requested (0)
==================================================================
BUG: KASAN: use-after-free in ifname_compare_aligned include/linux/netfilter/x_tables.h:412 [inline]
BUG: KASAN: use-after-free in ip_packet_match net/ipv4/netfilter/ip_tables.c:64 [inline]
BUG: KASAN: use-after-free in ipt_do_table+0x6ba/0x1510 net/ipv4/netfilter/ip_tables.c:284
Read of size 8 at addr ffff888127ba0000 by task syz.3.11/355

CPU: 1 PID: 355 Comm: syz.3.11 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:88
 dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:427 [inline]
 kasan_report+0x10f/0x150 mm/kasan/report.c:444
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report_generic.c:309
 ifname_compare_aligned include/linux/netfilter/x_tables.h:412 [inline]
 ip_packet_match net/ipv4/netfilter/ip_tables.c:64 [inline]
 ipt_do_table+0x6ba/0x1510 net/ipv4/netfilter/ip_tables.c:284
 iptable_mangle_hook+0x196/0x4d0 net/ipv4/netfilter/iptable_mangle.c:79
 nf_hook_entry_hookfn include/linux/netfilter.h:143 [inline]
 nf_hook_slow+0xbc/0x200 net/netfilter/core.c:590
 nf_hook include/linux/netfilter.h:260 [inline]
 NF_HOOK_COND include/linux/netfilter.h:293 [inline]
 ip_mc_output+0x61c/0x8d0 net/ipv4/ip_output.c:415
 dst_output include/net/dst.h:453 [inline]
 ip_local_out net/ipv4/ip_output.c:126 [inline]
 ip_send_skb+0xb4/0x140 net/ipv4/ip_output.c:1594
 udp_send_skb+0x8e6/0x10f0 net/ipv4/udp.c:991
 udp_sendmsg+0x176a/0x2110 net/ipv4/udp.c:1279
 inet_sendmsg+0xa5/0xc0 net/ipv4/af_inet.c:830
 sock_sendmsg_nosec net/socket.c:704 [inline]
 __sock_sendmsg net/socket.c:716 [inline]
 ____sys_sendmsg+0x5be/0x8f0 net/socket.c:2436
 ___sys_sendmsg+0x236/0x2e0 net/socket.c:2490
 __sys_sendmmsg+0x2ba/0x4e0 net/socket.c:2576
 __do_sys_sendmmsg net/socket.c:2605 [inline]
 __se_sys_sendmmsg net/socket.c:2602 [inline]
 __x64_sys_sendmmsg+0xa0/0xb0 net/socket.c:2602
 x64_sys_call+0x6c6/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:308
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f840c5991d9
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:00007f840aff2028 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007f840c820fa0 RCX: 00007f840c5991d9
RDX: 000000000800001d RSI: 0000200000007fc0 RDI: 0000000000000009
RBP: 00007f840c630888 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000300 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f840c821038 R14: 00007f840c820fa0 R15: 00007ffdd71e2e08
 </TASK>

Allocated by task 0:
(stack is not available)

The buggy address belongs to the object at ffff888127ba0000
 which belongs to the cache shmem_inode_cache of size 856
The buggy address is located 0 bytes inside of
 856-byte region [ffff888127ba0000, ffff888127ba0358)
The buggy address belongs to the page:
page:ffffea00049ee800 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x127ba0
head:ffffea00049ee800 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 0000000000000000 dead000000000122 ffff8881001c5500
raw: 0000000000000000 0000000080100010 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 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 363, ts 24164268397, free_ts 23997601547
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x192/0x1b0 mm/page_alloc.c:2607
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2613
 get_page_from_freelist+0x2c3a/0x2cd0 mm/page_alloc.c:4487
 __alloc_pages+0x1a2/0x460 mm/page_alloc.c:5824
 alloc_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1937 [inline]
 new_slab+0xa0/0x4d0 mm/slub.c:2000
 ___slab_alloc+0x3ac/0x840 mm/slub.c:3033
 __slab_alloc+0x49/0x90 mm/slub.c:3120
 slab_alloc_node mm/slub.c:3211 [inline]
 slab_alloc mm/slub.c:3255 [inline]
 kmem_cache_alloc+0x138/0x260 mm/slub.c:3260
 shmem_alloc_inode+0x1a/0x30 mm/shmem.c:3791
 alloc_inode fs/inode.c:264 [inline]
 new_inode_pseudo+0x62/0x210 fs/inode.c:1011
 new_inode+0x28/0x1e0 fs/inode.c:1040
 shmem_get_inode+0x343/0x9d0 mm/shmem.c:2292
 __shmem_file_setup+0x165/0x2b0 mm/shmem.c:4134
 shmem_kernel_file_setup mm/shmem.c:4164 [inline]
 shmem_zero_setup+0x99/0x1e0 mm/shmem.c:4208
 __mmap_region mm/mmap.c:1853 [inline]
 mmap_region+0x1247/0x1700 mm/mmap.c:2959
 do_mmap+0x812/0xf10 mm/mmap.c:1598
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1474 [inline]
 free_pcp_prepare mm/page_alloc.c:1546 [inline]
 free_unref_page_prepare+0x5fa/0x600 mm/page_alloc.c:3536
 free_unref_page+0xae/0x540 mm/page_alloc.c:3618
 free_the_page mm/page_alloc.c:805 [inline]
 __free_pages+0x6c/0x100 mm/page_alloc.c:5900
 free_nonslab_page+0x86/0xc0 mm/slub.c:3564
 kfree+0x19a/0x270 mm/slub.c:4585
 kvfree+0x35/0x40 mm/util.c:661
 netdev_freemem+0x3f/0x60 net/core/dev.c:10880
 netdev_release+0x7f/0xb0 net/core/net-sysfs.c:1903
 device_release+0x96/0x1c0 drivers/base/core.c:-1
 kobject_cleanup lib/kobject.c:713 [inline]
 kobject_release lib/kobject.c:744 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x18a/0x270 lib/kobject.c:761
 netdev_run_todo+0x7dc/0x950 net/core/dev.c:10736
 rtnl_unlock net/core/rtnetlink.c:112 [inline]
 rtnetlink_rcv_msg+0xa38/0xcb0 net/core/rtnetlink.c:5663
 netlink_rcv_skb+0x1e9/0x430 net/netlink/af_netlink.c:2520
 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:5680
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x86c/0xa30 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x879/0xb80 net/netlink/af_netlink.c:1923

Memory state around the buggy address:
 ffff888127b9ff00: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
 ffff888127b9ff80: fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe fe
>ffff888127ba0000: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                   ^
 ffff888127ba0080: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888127ba0100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/10 06:03 android13-5.15-lts d6c8aee048e0 4f92358f .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: use-after-free Read in ipt_do_table
* Struck through repros no longer work on HEAD.