KASAN: slab-out-of-bounds Read in ext4_ext_correct_indexes

Status: fixed on 2026/05/21 07:50
Subsystems: ext4
[Documentation on labels]
Reported-by: syzbot+04c4e65cab786a2e5b7e@syzkaller.appspotmail.com
Fix commit: 2acb5c12ebd8 ext4: validate p_idx bounds in ext4_ext_correct_indexes
First crash: 437d, last: 146d
Cause bisection: failed (error log, bisect log)
  
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Discussions (5)
Title Replies (including bot) Last reply
[PATCH 5.10/5.15] ext4: validate p_idx bounds in ext4_ext_correct_indexes 2 (2) 2026/06/11 00:45
[PATCH 6.6.y] ext4: validate p_idx bounds in ext4_ext_correct_indexes 2 (2) 2026/05/08 08:07
[PATCH 6.1.y] ext4: validate p_idx bounds in ext4_ext_correct_indexes 1 (1) 2026/05/08 06:58
[PATCH] ext4: validate p_idx bounds in ext4_ext_correct_indexes 1 (1) 2026/03/04 07:32
[syzbot] [ext4?] KASAN: slab-out-of-bounds Read in ext4_ext_correct_indexes 0 (1) 2025/05/26 13:47
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-6-1 KASAN: slab-out-of-bounds Read in ext4_ext_correct_indexes origin:upstream 17 syz error 1 189d 189d 0/2 auto-obsoleted due to no activity on 2026/04/28 09:22
▶ ▼ Last patch testing requests (10)
Created Duration User Patch Repo Result
2026/03/26 13:29 3h14m retest repro linux-next error
2026/03/12 09:42 22m retest repro upstream report log
2026/03/12 09:42 23m retest repro upstream report log
2026/03/12 09:42 15m retest repro upstream report log
2026/02/04 02:46 16m retest repro linux-next error
2026/01/20 14:31 21m retest repro upstream report log
2026/01/04 08:56 24m retest repro linux-next report log
2025/11/24 23:56 24m retest repro linux-next report log
2025/11/10 22:58 22m retest repro upstream report log
2025/09/04 22:11 21m retest repro linux-next report log
▶ ▼ Fix bisection attempts (2)
Created Duration User Patch Repo Result
2025/09/01 16:48 26m bisect fix upstream error job log
2025/07/27 17:28 3h00m bisect fix upstream OK (0) job log log

Sample crash report:
==================================================================
BUG: KASAN: slab-out-of-bounds in ext4_ext_correct_indexes+0x72/0x5b0 fs/ext4/extents.c:1710
Read of size 8 at addr ffff88807b361f50 by task syz-executor191/6954

CPU: 0 UID: 0 PID: 6954 Comm: syz-executor191 Not tainted 6.15.0-rc7-syzkaller-00152-gd0c22de9995b #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:408 [inline]
 print_report+0xb4/0x290 mm/kasan/report.c:521
 kasan_report+0x118/0x150 mm/kasan/report.c:634
 ext4_ext_correct_indexes+0x72/0x5b0 fs/ext4/extents.c:1710
 ext4_ext_insert_extent+0x1fdd/0x4af0 fs/ext4/extents.c:2186
 ext4_ext_map_blocks+0x179c/0x67c0 fs/ext4/extents.c:4400
 ext4_map_create_blocks fs/ext4/inode.c:520 [inline]
 ext4_map_blocks+0x807/0x1740 fs/ext4/inode.c:706
 _ext4_get_block+0x200/0x4c0 fs/ext4/inode.c:785
 ext4_get_block_unwritten+0x2e/0x100 fs/ext4/inode.c:818
 ext4_block_write_begin+0x543/0x1290 fs/ext4/inode.c:1067
 ext4_write_begin+0x6f6/0x12c0 fs/ext4/ext4_jbd2.h:-1
 ext4_da_write_begin+0x33a/0xa60 fs/ext4/inode.c:2932
 generic_perform_write+0x2c4/0x910 mm/filemap.c:4103
 ext4_buffered_write_iter+0xce/0x3a0 fs/ext4/file.c:299
 ext4_file_write_iter+0x298/0x1bc0 fs/ext4/file.c:-1
 new_sync_write fs/read_write.c:591 [inline]
 vfs_write+0x54b/0xa90 fs/read_write.c:684
 ksys_pwrite64 fs/read_write.c:791 [inline]
 __do_sys_pwrite64 fs/read_write.c:799 [inline]
 __se_sys_pwrite64 fs/read_write.c:796 [inline]
 __x64_sys_pwrite64+0x193/0x220 fs/read_write.c:796
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fcafd410be9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 c1 1f 00 00 90 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fcafcbb4168 EFLAGS: 00000246 ORIG_RAX: 0000000000000012
RAX: ffffffffffffffda RBX: 00007fcafd4984a8 RCX: 00007fcafd410be9
RDX: 000000000000fdef RSI: 0000200000000140 RDI: 0000000000000004
RBP: 00007fcafd4984a0 R08: 00007fcafcbb46c0 R09: 0000000000000000
R10: 000000000000fecc R11: 0000000000000246 R12: 00007fcafd4984ac
R13: 000000000000000b R14: 00007fff140f2480 R15: 00007fff140f2568
 </TASK>

Allocated by task 12:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
 poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:394
 kasan_kmalloc include/linux/kasan.h:260 [inline]
 __do_kmalloc_node mm/slub.c:4327 [inline]
 __kmalloc_noprof+0x27a/0x4f0 mm/slub.c:4339
 kmalloc_noprof include/linux/slab.h:909 [inline]
 kzalloc_noprof include/linux/slab.h:1039 [inline]
 cfg80211_inform_single_bss_data+0x905/0x1ac0 net/wireless/scan.c:2339
 cfg80211_inform_bss_data+0x1fb/0x3b20 net/wireless/scan.c:3222
 cfg80211_inform_bss_frame_data+0x362/0x700 net/wireless/scan.c:3317
 ieee80211_bss_info_update+0x746/0x9e0 net/mac80211/scan.c:226
 ieee80211_rx_bss_info net/mac80211/ibss.c:1102 [inline]
 ieee80211_rx_mgmt_probe_beacon net/mac80211/ibss.c:1581 [inline]
 ieee80211_ibss_rx_queued_mgmt+0xa36/0x2ae0 net/mac80211/ibss.c:1608
 ieee80211_iface_process_skb net/mac80211/iface.c:1625 [inline]
 ieee80211_iface_work+0x806/0xfe0 net/mac80211/iface.c:1679
 cfg80211_wiphy_work+0x2df/0x460 net/wireless/core.c:435
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0xade/0x17a0 kernel/workqueue.c:3319
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400
 kthread+0x711/0x8a0 kernel/kthread.c:464
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Last potentially related work creation:
 kasan_save_stack+0x3e/0x60 mm/kasan/common.c:47
 kasan_record_aux_stack+0xbc/0xd0 mm/kasan/generic.c:548
 kvfree_call_rcu+0xbb/0x410 mm/slab_common.c:1962
 cfg80211_update_known_bss+0x634/0x1330 net/wireless/scan.c:1925
 __cfg80211_bss_update+0x147/0x2120 net/wireless/scan.c:1972
 cfg80211_inform_single_bss_data+0xba9/0x1ac0 net/wireless/scan.c:2363
 cfg80211_inform_bss_data+0x1fb/0x3b20 net/wireless/scan.c:3222
 cfg80211_inform_bss_frame_data+0x362/0x700 net/wireless/scan.c:3317
 ieee80211_bss_info_update+0x746/0x9e0 net/mac80211/scan.c:226
 ieee80211_scan_rx+0x527/0x9b0 net/mac80211/scan.c:340
 __ieee80211_rx_handle_packet net/mac80211/rx.c:5179 [inline]
 ieee80211_rx_list+0x22fc/0x2d80 net/mac80211/rx.c:5416
 ieee80211_rx_napi+0x1a8/0x3d0 net/mac80211/rx.c:5439
 ieee80211_rx include/net/mac80211.h:5179 [inline]
 ieee80211_handle_queued_frames+0xe8/0x1f0 net/mac80211/main.c:441
 tasklet_action_common+0x369/0x580 kernel/softirq.c:829
 handle_softirqs+0x283/0x870 kernel/softirq.c:579
 __do_softirq kernel/softirq.c:613 [inline]
 invoke_softirq kernel/softirq.c:453 [inline]
 __irq_exit_rcu+0xca/0x1f0 kernel/softirq.c:680
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:696
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1049 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1049
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702

The buggy address belongs to the object at ffff88807b361f00
 which belongs to the cache kmalloc-96 of size 96
The buggy address is located 8 bytes to the right of
 allocated 72-byte region [ffff88807b361f00, ffff88807b361f48)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7b361
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000000 ffff88801a041280 ffffea0000bd3a40 dead000000000002
raw: 0000000000000000 0000000000200020 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 0x52820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 36, tgid 36 (kworker/u8:2), ts 101928270930, free_ts 101772582052
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1d8/0x230 mm/page_alloc.c:1714
 prep_new_page mm/page_alloc.c:1722 [inline]
 get_page_from_freelist+0x21c7/0x22a0 mm/page_alloc.c:3684
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:4966
 alloc_pages_mpol+0x232/0x4a0 mm/mempolicy.c:2301
 alloc_slab_page mm/slub.c:2450 [inline]
 allocate_slab+0x8a/0x3b0 mm/slub.c:2618
 new_slab mm/slub.c:2672 [inline]
 ___slab_alloc+0xbfc/0x1480 mm/slub.c:3858
 __slab_alloc mm/slub.c:3948 [inline]
 __slab_alloc_node mm/slub.c:4023 [inline]
 slab_alloc_node mm/slub.c:4184 [inline]
 __kmalloc_cache_noprof+0x296/0x3d0 mm/slub.c:4353
 kmalloc_noprof include/linux/slab.h:905 [inline]
 kzalloc_noprof include/linux/slab.h:1039 [inline]
 nsim_fib_event_schedule_work drivers/net/netdevsim/fib.c:990 [inline]
 nsim_fib_event_nb+0x187/0x1080 drivers/net/netdevsim/fib.c:1043
 notifier_call_chain+0x1b3/0x3e0 kernel/notifier.c:85
 atomic_notifier_call_chain+0xda/0x180 kernel/notifier.c:223
 call_fib_notifiers+0x31/0x60 net/core/fib_notifier.c:35
 call_fib6_entry_notifiers net/ipv6/ip6_fib.c:397 [inline]
 fib6_add_rt2node net/ipv6/ip6_fib.c:1231 [inline]
 fib6_add+0x1a78/0x4360 net/ipv6/ip6_fib.c:1488
 __ip6_ins_rt net/ipv6/route.c:1351 [inline]
 ip6_ins_rt+0xc8/0x120 net/ipv6/route.c:1361
 __ipv6_ifa_notify+0x63f/0xac0 net/ipv6/addrconf.c:6286
 ipv6_ifa_notify net/ipv6/addrconf.c:6325 [inline]
 addrconf_dad_completed+0x180/0xd60 net/ipv6/addrconf.c:4324
 addrconf_dad_work+0xc36/0x14b0 net/ipv6/addrconf.c:-1
page last free pid 5847 tgid 5847 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1258 [inline]
 __free_frozen_pages+0xb05/0xcd0 mm/page_alloc.c:2721
 discard_slab mm/slub.c:2716 [inline]
 __put_partials+0x161/0x1c0 mm/slub.c:3185
 put_cpu_partial+0x17c/0x250 mm/slub.c:3260
 __slab_free+0x2f7/0x400 mm/slub.c:4512
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x9a/0x140 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:329
 kasan_slab_alloc include/linux/kasan.h:250 [inline]
 slab_post_alloc_hook mm/slub.c:4147 [inline]
 slab_alloc_node mm/slub.c:4196 [inline]
 __do_kmalloc_node mm/slub.c:4326 [inline]
 __kmalloc_noprof+0x224/0x4f0 mm/slub.c:4339
 kmalloc_noprof include/linux/slab.h:909 [inline]
 kzalloc_noprof include/linux/slab.h:1039 [inline]
 tomoyo_encode2 security/tomoyo/realpath.c:45 [inline]
 tomoyo_encode+0x28b/0x550 security/tomoyo/realpath.c:80
 tomoyo_realpath_from_path+0x58d/0x5d0 security/tomoyo/realpath.c:283
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_path_perm+0x213/0x4b0 security/tomoyo/file.c:822
 tomoyo_path_unlink+0xa2/0xe0 security/tomoyo/tomoyo.c:162
 security_path_unlink+0x167/0x360 security/security.c:1965
 do_unlinkat+0x2de/0x560 fs/namei.c:4640
 __do_sys_unlink fs/namei.c:4689 [inline]
 __se_sys_unlink fs/namei.c:4687 [inline]
 __x64_sys_unlink+0x47/0x50 fs/namei.c:4687
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94

Memory state around the buggy address:
 ffff88807b361e00: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
 ffff88807b361e80: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc
>ffff88807b361f00: 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc
                                                 ^
 ffff88807b361f80: fa fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
 ffff88807b362000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================

Crashes (7):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/05/25 17:26 upstream d0c22de9995b ed351ea7 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-upstream-fs KASAN: slab-out-of-bounds Read in ext4_ext_correct_indexes
2026/02/26 05:12 upstream d9d32e5bd5a4 e0f78d93 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-upstream-fs KASAN: use-after-free Read in ext4_ext_correct_indexes
2026/02/26 03:23 upstream d9d32e5bd5a4 e0f78d93 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-upstream-fs KASAN: slab-use-after-free Read in ext4_ext_correct_indexes
2025/12/20 21:49 linux-next cc3aa43b44bd d6526ea3 .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci-upstream-linux-next-kasan-gce-root KASAN: slab-out-of-bounds Read in ext4_ext_correct_indexes
2026/02/26 08:44 upstream d9d32e5bd5a4 e0f78d93 .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro #1 (corrupt fs)] [mounted in repro #2 (corrupt fs)] [mounted in repro #3 (corrupt fs)] [mounted in repro #4] [mounted in repro #5 (clean fs)] [mounted in repro #6 (corrupt fs)] ci2-upstream-fs KASAN: use-after-free Read in ext4_ext_correct_indexes
2025/06/11 16:15 linux-next 19a60293b992 5d7e17ca .config console log report syz / log [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci-upstream-linux-next-kasan-gce-root KASAN: use-after-free Read in ext4_ext_correct_indexes
2025/05/25 16:12 upstream d0c22de9995b ed351ea7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-fs KASAN: slab-out-of-bounds Read in ext4_ext_correct_indexes
* Struck through repros no longer work on HEAD.