syzbot


KASAN: use-after-free Read in ext4_listxattr

Status: upstream: reported C repro on 2026/05/18 05:03
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+497e40b21797638daf43@syzkaller.appspotmail.com
First crash: 61d, last: 4d00h
Bug presence (2)
Date Name Commit Repro Result
2026/05/24 lts (merge base) 93741761e5e3 C [report] lost connection to test machine
2026/05/24 upstream (ToT) 4cbfe4502e3d C [report] lost connection to test machine
Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-5-10 KASAN: use-after-free Read in ext4_listxattr 19 C 7 4d00h 44d 0/2 upstream: reported C repro on 2026/06/04 20:13
Last patch testing requests (1)
Created Duration User Patch Repo Result
2026/06/01 12:18 14m retest repro android13-5.15-lts log
Fix bisection attempts (1)
Created Duration User Patch Repo Result
2026/06/17 22:49 1h29m bisect fix android13-5.15-lts OK (0) job log log

Sample crash report:
EXT4-fs (loop2): Ignoring removed oldalloc option
EXT4-fs (loop2): Ignoring removed mblk_io_submit option
EXT4-fs (loop2): encrypted files will use data=ordered instead of data journaling mode
EXT4-fs (loop2): 1 truncate cleaned up
EXT4-fs (loop2): mounted filesystem without journal. Opts: errors=remount-ro,mblk_io_submit,mblk_io_submit,resgid=0x0000000000000000,oldalloc,mblk_io_submit,nogrpid,. Quota mode: none.
==================================================================
BUG: KASAN: use-after-free in ext4_xattr_list_entries fs/ext4/xattr.c:670 [inline]
BUG: KASAN: use-after-free in ext4_xattr_ibody_list fs/ext4/xattr.c:740 [inline]
BUG: KASAN: use-after-free in ext4_listxattr+0x4a9/0xc60 fs/ext4/xattr.c:765
Read of size 4 at addr ffff88811eee0018 by task syz.2.19/379

CPU: 0 PID: 379 Comm: syz.2.19 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/25/2026
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_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:308
 ext4_xattr_list_entries fs/ext4/xattr.c:670 [inline]
 ext4_xattr_ibody_list fs/ext4/xattr.c:740 [inline]
 ext4_listxattr+0x4a9/0xc60 fs/ext4/xattr.c:765
 vfs_listxattr fs/xattr.c:448 [inline]
 listxattr+0x28f/0x300 fs/xattr.c:783
 path_listxattr+0xe1/0x1b0 fs/xattr.c:807
 __do_sys_listxattr fs/xattr.c:819 [inline]
 __se_sys_listxattr fs/xattr.c:816 [inline]
 __x64_sys_listxattr+0x80/0x90 fs/xattr.c:816
 x64_sys_call+0xd7/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:195
 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: 0033:0x7f6dbdca2e59
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:00007ffeafe85908 EFLAGS: 00000246 ORIG_RAX: 00000000000000c2
RAX: ffffffffffffffda RBX: 00007f6dbdf2afa0 RCX: 00007f6dbdca2e59
RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000200000000140
RBP: 00007f6dbdd38e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6dbdf2afac R14: 00007f6dbdf2afa0 R15: 00007f6dbdf2afa0
 </TASK>

Allocated by task 369:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:433 [inline]
 ____kasan_kmalloc mm/kasan/common.c:512 [inline]
 __kasan_kmalloc+0xd4/0x100 mm/kasan/common.c:521
 kasan_kmalloc include/linux/kasan.h:227 [inline]
 __kmalloc+0x13d/0x2c0 mm/slub.c:4436
 kmalloc include/linux/slab.h:624 [inline]
 kzalloc include/linux/slab.h:750 [inline]
 fib6_info_alloc+0x34/0xe0 net/ipv6/ip6_fib.c:155
 ip6_route_info_create+0x51b/0x14d0 net/ipv6/route.c:3783
 addrconf_f6i_alloc+0x19c/0x3f0 net/ipv6/route.c:4583
 ipv6_add_addr+0x442/0xd90 net/ipv6/addrconf.c:1125
 inet6_addr_add+0x446/0x9d0 net/ipv6/addrconf.c:3022
 inet6_rtm_newaddr+0x6e7/0x9c0 net/ipv6/addrconf.c:4975
 rtnetlink_rcv_msg+0x9fd/0xcb0 net/core/rtnetlink.c:5654
 netlink_rcv_skb+0x1e9/0x430 net/netlink/af_netlink.c:2516
 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:5672
 netlink_unicast_kernel net/netlink/af_netlink.c:1322 [inline]
 netlink_unicast+0x86c/0xa30 net/netlink/af_netlink.c:1348
 netlink_sendmsg+0x879/0xb80 net/netlink/af_netlink.c:1927
 sock_sendmsg_nosec net/socket.c:704 [inline]
 __sock_sendmsg net/socket.c:716 [inline]
 __sys_sendto+0x46d/0x620 net/socket.c:2063
 __do_sys_sendto net/socket.c:2075 [inline]
 __se_sys_sendto net/socket.c:2071 [inline]
 __x64_sys_sendto+0xe5/0x100 net/socket.c:2071
 x64_sys_call+0x178/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:45
 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

Freed by task 13:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4a/0x70 mm/kasan/common.c:45
 kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370
 ____kasan_slab_free+0x125/0x160 mm/kasan/common.c:365
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:373
 kasan_slab_free include/linux/kasan.h:193 [inline]
 slab_free_hook mm/slub.c:1728 [inline]
 slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1754
 slab_free mm/slub.c:3526 [inline]
 kfree+0xc4/0x270 mm/slub.c:4588
 fib6_info_destroy_rcu+0x171/0x1c0 net/ipv6/ip6_fib.c:178
 rcu_do_batch+0x4c1/0xbf0 kernel/rcu/tree.c:2523
 rcu_core+0x4a3/0xef0 kernel/rcu/tree.c:2763
 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2776
 handle_softirqs+0x250/0x560 kernel/softirq.c:583
 run_ksoftirqd+0x28/0x40 kernel/softirq.c:959
 smpboot_thread_fn+0x446/0x880 kernel/smpboot.c:164
 kthread+0x3f5/0x4f0 kernel/kthread.c:337
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287

Last potentially related work creation:
 kasan_save_stack+0x3a/0x60 mm/kasan/common.c:38
 __kasan_record_aux_stack+0xd2/0x100 mm/kasan/generic.c:348
 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:358
 __call_rcu_common kernel/rcu/tree.c:3011 [inline]
 call_rcu+0x10b/0xf60 kernel/rcu/tree.c:3129
 fib6_info_release include/net/ip6_fib.h:349 [inline]
 fixup_permanent_addr net/ipv6/addrconf.c:3544 [inline]
 addrconf_permanent_addr+0x302/0x940 net/ipv6/addrconf.c:3572
 addrconf_notify+0x752/0xe00 net/ipv6/addrconf.c:3640
 notifier_call_chain kernel/notifier.c:83 [inline]
 raw_notifier_call_chain+0x90/0x100 kernel/notifier.c:391
 call_netdevice_notifiers_info net/core/dev.c:2070 [inline]
 call_netdevice_notifiers_extack net/core/dev.c:2082 [inline]
 call_netdevice_notifiers net/core/dev.c:2096 [inline]
 __dev_notify_flags+0x2f4/0x5b0 net/core/dev.c:8925
 dev_change_flags+0xe3/0x1a0 net/core/dev.c:8963
 do_setlink+0xc95/0x2970 net/core/rtnetlink.c:2783
 __rtnl_newlink net/core/rtnetlink.c:3454 [inline]
 rtnl_newlink+0x1598/0x1900 net/core/rtnetlink.c:3576
 rtnetlink_rcv_msg+0x9fd/0xcb0 net/core/rtnetlink.c:5654
 netlink_rcv_skb+0x1e9/0x430 net/netlink/af_netlink.c:2516
 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:5672
 netlink_unicast_kernel net/netlink/af_netlink.c:1322 [inline]
 netlink_unicast+0x86c/0xa30 net/netlink/af_netlink.c:1348
 netlink_sendmsg+0x879/0xb80 net/netlink/af_netlink.c:1927
 sock_sendmsg_nosec net/socket.c:704 [inline]
 __sock_sendmsg net/socket.c:716 [inline]
 __sys_sendto+0x46d/0x620 net/socket.c:2063
 __do_sys_sendto net/socket.c:2075 [inline]
 __se_sys_sendto net/socket.c:2071 [inline]
 __x64_sys_sendto+0xe5/0x100 net/socket.c:2071
 x64_sys_call+0x178/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:45
 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

The buggy address belongs to the object at ffff88811eee0000
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 24 bytes inside of
 512-byte region [ffff88811eee0000, ffff88811eee0200)
The buggy address belongs to the page:
page:ffffea00047bb800 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x11eee0
head:ffffea00047bb800 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head|zone=1)
raw: 4000000000010200 0000000000000000 dead000000000122 ffff888100042f00
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 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 369, ts 27642740766, free_ts 16771460306
 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]
 __kmalloc+0x16a/0x2c0 mm/slub.c:4432
 __kmalloc_node include/linux/slab.h:487 [inline]
 kmalloc_node include/linux/slab.h:642 [inline]
 kzalloc_node include/linux/slab.h:761 [inline]
 qdisc_alloc+0x79/0x7b0 net/sched/sch_generic.c:891
 qdisc_create_dflt+0x6b/0x390 net/sched/sch_generic.c:953
 attach_one_default_qdisc net/sched/sch_generic.c:1116 [inline]
 netdev_for_each_tx_queue include/linux/netdevice.h:2411 [inline]
 attach_default_qdiscs net/sched/sch_generic.c:1134 [inline]
 dev_activate+0x28e/0x1030 net/sched/sch_generic.c:1193
 __dev_open+0x3e9/0x500 net/core/dev.c:1567
 __dev_change_flags+0x1e4/0x6a0 net/core/dev.c:8887
 dev_change_flags+0x80/0x1a0 net/core/dev.c:8958
 do_setlink+0xc95/0x2970 net/core/rtnetlink.c:2783
 __rtnl_newlink net/core/rtnetlink.c:3454 [inline]
 rtnl_newlink+0x1598/0x1900 net/core/rtnetlink.c:3576
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_compound_page+0x78/0xa0 mm/page_alloc.c:828
 destroy_compound_page include/linux/mm.h:1000 [inline]
 __put_compound_page+0x77/0xb0 mm/swap.c:111
 __put_page+0xbc/0xe0 mm/swap.c:127
 put_page include/linux/mm.h:1306 [inline]
 __skb_frag_unref include/linux/skbuff.h:3275 [inline]
 skb_release_data+0x37c/0xa20 net/core/skbuff.c:673
 skb_release_all net/core/skbuff.c:743 [inline]
 __kfree_skb+0x50/0x70 net/core/skbuff.c:757
 sk_eat_skb include/net/sock.h:2800 [inline]
 tcp_recvmsg_locked+0x13d1/0x24f0 net/ipv4/tcp.c:2520
 tcp_recvmsg+0x233/0x770 net/ipv4/tcp.c:2566
 inet_recvmsg+0x13a/0x470 net/ipv4/af_inet.c:861
 sock_recvmsg_nosec net/socket.c:967 [inline]
 sock_recvmsg net/socket.c:985 [inline]
 sock_read_iter+0x2c2/0x380 net/socket.c:1058
 call_read_iter include/linux/fs.h:2206 [inline]
 new_sync_read fs/read_write.c:404 [inline]
 vfs_read+0x6c0/0xc20 fs/read_write.c:485
 ksys_read+0x14a/0x260 fs/read_write.c:623
 __do_sys_read fs/read_write.c:633 [inline]
 __se_sys_read fs/read_write.c:631 [inline]
 __x64_sys_read+0x7b/0x90 fs/read_write.c:631
 x64_sys_call+0x96d/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:1
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80

Memory state around the buggy address:
 ffff88811eedff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88811eedff80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88811eee0000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff88811eee0080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88811eee0100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (9):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/15 01:20 android13-5.15-lts bf3c87ba3144 2130f682 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-5-15 KASAN: use-after-free Read in ext4_listxattr
2026/07/15 00:50 android13-5.15-lts bf3c87ba3144 2130f682 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-5-15 KASAN: use-after-free Read in ext4_listxattr
2026/07/15 00:21 android13-5.15-lts bf3c87ba3144 2130f682 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-5-15 KASAN: use-after-free Read in ext4_listxattr
2026/07/01 21:57 android13-5.15-lts c85054db4618 27192279 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-5-15 KASAN: use-after-free Read in ext4_listxattr
2026/07/01 21:18 android13-5.15-lts c85054db4618 27192279 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-5-15 KASAN: use-after-free Read in ext4_listxattr
2026/05/18 05:02 android13-5.15-lts 7f4b368e0410 de5aae85 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro #1 (corrupt fs)] [mounted in repro #2 (corrupt fs)] ci2-android-5-15 KASAN: use-after-free Read in ext4_listxattr
2026/07/14 23:59 android13-5.15-lts bf3c87ba3144 2130f682 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-5-15 KASAN: slab-out-of-bounds Read in ext4_listxattr
2026/07/01 20:56 android13-5.15-lts c85054db4618 27192279 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci2-android-5-15 KASAN: slab-out-of-bounds Read in ext4_listxattr
2026/06/27 04:26 android13-5.15-lts c85054db4618 fb92f11c .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-5-15 KASAN: slab-out-of-bounds Read in ext4_listxattr
* Struck through repros no longer work on HEAD.