syzbot

==================================================================
BUG: KASAN: use-after-free in ext4_ext_binsearch fs/ext4/extents.c:837 [inline]
BUG: KASAN: use-after-free in ext4_find_extent+0xbeb/0xe20 fs/ext4/extents.c:953
Read of size 4 at addr ffff88810efce0d8 by task kworker/u4:0/8

CPU: 1 PID: 8 Comm: kworker/u4:0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: writeback wb_workfn (flush-7:2)
Call Trace:
 <TASK>
 __dump_stack+0x21/0x24 lib/dump_stack.c:88
 dump_stack_lvl+0xee/0x150 lib/dump_stack.c:106
 print_address_description+0x71/0x200 mm/kasan/report.c:316
 print_report+0x4a/0x60 mm/kasan/report.c:420
 kasan_report+0x122/0x150 mm/kasan/report.c:524
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:350
 ext4_ext_binsearch fs/ext4/extents.c:837 [inline]
 ext4_find_extent+0xbeb/0xe20 fs/ext4/extents.c:953
 ext4_ext_map_blocks+0x1dc/0x6060 fs/ext4/extents.c:4166
 ext4_map_blocks+0x9cb/0x1b60 fs/ext4/inode.c:679
 mpage_map_one_extent fs/ext4/inode.c:2435 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2488 [inline]
 ext4_writepages+0x1260/0x3020 fs/ext4/inode.c:2856
 do_writepages+0x3a9/0x5e0 mm/page-writeback.c:2494
 __writeback_single_inode+0xc6/0xad0 fs/fs-writeback.c:1612
 writeback_sb_inodes+0x9b8/0x1550 fs/fs-writeback.c:1903
 wb_writeback+0x3f1/0x980 fs/fs-writeback.c:2079
 wb_do_writeback fs/fs-writeback.c:2226 [inline]
 wb_workfn+0x350/0xda0 fs/fs-writeback.c:2266
 process_one_work+0x71f/0xc40 kernel/workqueue.c:2302
 worker_thread+0xa29/0x11f0 kernel/workqueue.c:2449
 kthread+0x281/0x320 kernel/kthread.c:386
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>

Allocated by task 301:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:52
 kasan_save_alloc_info+0x25/0x30 mm/kasan/generic.c:505
 ____kasan_kmalloc mm/kasan/common.c:379 [inline]
 __kasan_kmalloc+0x95/0xb0 mm/kasan/common.c:388
 kasan_kmalloc include/linux/kasan.h:212 [inline]
 kmalloc_trace+0x40/0xb0 mm/slab_common.c:1033
 kmalloc include/linux/slab.h:563 [inline]
 kzalloc include/linux/slab.h:699 [inline]
 ref_tracker_alloc+0x139/0x430 lib/ref_tracker.c:85
 __netdev_tracker_alloc include/linux/netdevice.h:4085 [inline]
 netdev_tracker_alloc include/linux/netdevice.h:4097 [inline]
 fib6_nh_init+0x8e6/0x1ff0 net/ipv6/route.c:3668
 ip6_route_info_create+0xa66/0x1510 net/ipv6/route.c:3849
 addrconf_f6i_alloc+0x154/0x360 net/ipv6/route.c:4601
 fixup_permanent_addr net/ipv6/addrconf.c:3554 [inline]
 addrconf_permanent_addr+0x21f/0x8c0 net/ipv6/addrconf.c:3593
 addrconf_notify+0x7cf/0xe40 net/ipv6/addrconf.c:3665
 notifier_call_chain kernel/notifier.c:87 [inline]
 raw_notifier_call_chain+0xa1/0x110 kernel/notifier.c:455
 call_netdevice_notifiers_info net/core/dev.c:2009 [inline]
 call_netdevice_notifiers_extack net/core/dev.c:2047 [inline]
 call_netdevice_notifiers net/core/dev.c:2061 [inline]
 __dev_notify_flags+0x28f/0x500 net/core/dev.c:-1
 dev_change_flags+0xe8/0x1a0 net/core/dev.c:8730
 do_setlink+0xc3d/0x3d50 net/core/rtnetlink.c:2833
 __rtnl_newlink net/core/rtnetlink.c:3608 [inline]
 rtnl_newlink+0x17d9/0x2030 net/core/rtnetlink.c:3655
 rtnetlink_rcv_msg+0x9f4/0xcf0 net/core/rtnetlink.c:6153
 netlink_rcv_skb+0x1f2/0x440 net/netlink/af_netlink.c:2521
 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:6171
 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
 netlink_unicast+0x8ab/0xa30 net/netlink/af_netlink.c:1345
 netlink_sendmsg+0x8aa/0xbc0 net/netlink/af_netlink.c:1873
 sock_sendmsg_nosec net/socket.c:716 [inline]
 __sock_sendmsg net/socket.c:728 [inline]
 __sys_sendto+0x464/0x5e0 net/socket.c:2143
 __do_sys_sendto net/socket.c:2155 [inline]
 __se_sys_sendto net/socket.c:2151 [inline]
 __x64_sys_sendto+0xe5/0x100 net/socket.c:2151
 x64_sys_call+0x83/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:45
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Freed by task 8:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:52
 kasan_save_free_info+0x31/0x50 mm/kasan/generic.c:516
 ____kasan_slab_free+0x132/0x180 mm/kasan/common.c:241
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:249
 kasan_slab_free include/linux/kasan.h:178 [inline]
 slab_free_hook mm/slub.c:1750 [inline]
 slab_free_freelist_hook+0xc2/0x190 mm/slub.c:1776
 slab_free mm/slub.c:3712 [inline]
 __kmem_cache_free+0xb7/0x1b0 mm/slub.c:3728
 kfree+0x6f/0xf0 mm/slab_common.c:990
 ref_tracker_dir_exit+0x191/0x4c0 lib/ref_tracker.c:27
 free_netdev+0x27d/0x490 net/core/dev.c:10835
 netdev_run_todo+0xaa4/0xc00 net/core/dev.c:10476
 rtnl_unlock+0xe/0x10 net/core/rtnetlink.c:147
 default_device_exit_batch+0x9be/0xa50 net/core/dev.c:11481
 ops_exit_list net/core/net_namespace.c:177 [inline]
 cleanup_net+0x62d/0xb00 net/core/net_namespace.c:604
 process_one_work+0x71f/0xc40 kernel/workqueue.c:2302
 worker_thread+0xa29/0x11f0 kernel/workqueue.c:2449
 kthread+0x281/0x320 kernel/kthread.c:386
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

The buggy address belongs to the object at ffff88810efce0c0
 which belongs to the cache kmalloc-32 of size 32
The buggy address is located 24 bytes inside of
 32-byte region [ffff88810efce0c0, ffff88810efce0e0)

The buggy address belongs to the physical page:
page:ffffea00043bf380 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10efce
flags: 0x4000000000000200(slab|zone=1)
raw: 4000000000000200 0000000000000000 dead000000000001 ffff888100042600
raw: 0000000000000000 0000000000400040 00000001ffffffff 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 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 83, tgid 83 (start-stop-daem), ts 3915189756, free_ts 3914171511
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1f5/0x210 mm/page_alloc.c:2643
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2650
 get_page_from_freelist+0x2c7b/0x2cf0 mm/page_alloc.c:4554
 __alloc_pages+0x1c3/0x450 mm/page_alloc.c:5868
 alloc_slab_page+0x6e/0xf0 include/linux/gfp.h:-1
 allocate_slab mm/slub.c:1967 [inline]
 new_slab+0x98/0x3d0 mm/slub.c:2020
 ___slab_alloc+0x6bd/0xb20 mm/slub.c:3177
 __slab_alloc+0x5e/0xa0 mm/slub.c:3263
 slab_alloc_node mm/slub.c:3348 [inline]
 __kmem_cache_alloc_node+0x203/0x2c0 mm/slub.c:3423
 __do_kmalloc_node mm/slab_common.c:937 [inline]
 __kmalloc+0xa1/0x1e0 mm/slab_common.c:951
 kmalloc include/linux/slab.h:568 [inline]
 kzalloc include/linux/slab.h:699 [inline]
 lsm_cred_alloc security/security.c:540 [inline]
 security_prepare_creds+0x4e/0x150 security/security.c:1738
 prepare_creds+0x456/0x640 kernel/cred.c:294
 access_override_creds fs/open.c:377 [inline]
 do_faccessat+0x10e/0xa00 fs/open.c:441
 __do_sys_access fs/open.c:506 [inline]
 __se_sys_access fs/open.c:504 [inline]
 __x64_sys_access+0x61/0x70 fs/open.c:504
 x64_sys_call+0x5a0/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:22
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1551 [inline]
 free_pcp_prepare mm/page_alloc.c:1625 [inline]
 free_unref_page_prepare+0x742/0x750 mm/page_alloc.c:3589
 free_unref_page+0x8f/0x530 mm/page_alloc.c:3687
 free_the_page mm/page_alloc.c:836 [inline]
 __free_pages+0x67/0x100 mm/page_alloc.c:5957
 __vunmap+0x9af/0xb70 mm/vmalloc.c:2739
 free_work+0x5a/0x80 mm/vmalloc.c:98
 process_one_work+0x71f/0xc40 kernel/workqueue.c:2302
 worker_thread+0xa29/0x11f0 kernel/workqueue.c:2449
 kthread+0x281/0x320 kernel/kthread.c:386
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

Memory state around the buggy address:
 ffff88810efcdf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88810efce000: fa fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc
>ffff88810efce080: fa fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc
                                                    ^
 ffff88810efce100: fa fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc
 ffff88810efce180: fa fb fb fb fc fc fc fc 00 00 00 00 fc fc fc fc
==================================================================
EXT4-fs error (device loop2): ext4_map_blocks:745: inode #15: block 4069883428: comm kworker/u4:0: lblock 36 mapped to illegal pblock 4069883428 (length 1)
EXT4-fs (loop2): Delayed block allocation failed for inode 15 at logical offset 36 with max blocks 1 with error 117
EXT4-fs (loop2): This should not happen!! Data will be lost