KASAN: vmalloc-out-of-bounds Read in xfs_buf_lock

Status: upstream: reported C repro on 2026/02/01 05:42
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+80c9974e520006157dec@syzkaller.appspotmail.com
First crash: 197d, last: 83d
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2026/04/07 linux-6.1.y (ToT) 1989cd3d56e2 C [report] KASAN: vmalloc-out-of-bounds Read in xfs_buf_lock
2026/04/07 upstream (ToT) bfe62a454542 C Didn't crash
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.6 KASAN: vmalloc-out-of-bounds Read in xfs_buf_lock 17 2 84d 146d 0/2 upstream: reported on 2026/03/25 04:24
linux-6.1 KASAN: stack-out-of-bounds Read in xfs_buf_lock (2) 17 1 1018d 1018d 0/3 auto-obsoleted due to no activity on 2024/02/11 11:29
linux-6.6 KASAN: stack-out-of-bounds Read in xfs_buf_lock 17 1 305d 305d 0/2 auto-obsoleted due to no activity on 2026/01/25 03:43
upstream KASAN: stack-out-of-bounds Read in xfs_buf_lock xfs 17 syz, C error unreliable 866 573d 1344d 0/29 auto-obsoleted due to no activity on 2025/04/01 11:07
linux-6.1 KASAN: stack-out-of-bounds Read in xfs_buf_lock 17 1 1147d 1147d 0/3 auto-obsoleted due to no activity on 2023/10/06 04:59
▶ ▼ Fix bisection attempts (3)
Created Duration User Patch Repo Result
2026/07/07 04:26 2h58m fix candidate upstream OK (0) job log
2026/05/10 19:09 12m fix candidate upstream error job log
2026/04/08 09:42 3m fix candidate upstream error job log

Sample crash report:
XFS (loop1): Quotacheck needed: Please wait.
XFS (loop1): Quotacheck: Done.
==================================================================
BUG: KASAN: vmalloc-out-of-bounds in xfs_buf_lock+0x2a8/0x560 fs/xfs/xfs_buf.c:1118
Read of size 4 at addr ffffc90005d3795c by task syz.1.104/5242

CPU: 0 PID: 5242 Comm: syz.1.104 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:316 [inline]
 print_report+0xa8/0x210 mm/kasan/report.c:420
 kasan_report+0x10b/0x140 mm/kasan/report.c:524
 xfs_buf_lock+0x2a8/0x560 fs/xfs/xfs_buf.c:1118
 xfs_buf_delwri_submit_buffers+0x161/0xa30 fs/xfs/xfs_buf.c:2201
 xfs_buf_delwri_submit+0xc1/0x250 fs/xfs/xfs_buf.c:2279
 xfs_qm_shrink_scan+0x1a3/0x390 fs/xfs/xfs_qm.c:522
 do_shrink_slab+0x504/0xdb0 mm/vmscan.c:853
 shrink_slab+0x1dd/0x770 mm/vmscan.c:1013
 drop_slab_node mm/vmscan.c:1048 [inline]
 drop_slab+0x164/0x290 mm/vmscan.c:1058
 drop_caches_sysctl_handler+0xbe/0x160 fs/drop_caches.c:66
 proc_sys_call_handler+0x45e/0x6d0 fs/proc/proc_sysctl.c:602
 do_iter_readv_writev fs/read_write.c:-1 [inline]
 do_iter_write+0x642/0xb10 fs/read_write.c:861
 iter_file_splice_write+0x699/0xcc0 fs/splice.c:685
 do_splice_from fs/splice.c:763 [inline]
 direct_splice_actor+0xe1/0x130 fs/splice.c:950
 splice_direct_to_actor+0x48b/0xb90 fs/splice.c:896
 do_splice_direct+0x1ce/0x2f0 fs/splice.c:1002
 do_sendfile+0x5f3/0xea0 fs/read_write.c:1255
 __do_sys_sendfile64 fs/read_write.c:1317 [inline]
 __se_sys_sendfile64+0xdc/0x1a0 fs/read_write.c:1309
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f05bd79c819
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:00007ffee3aca918 EFLAGS: 00000246 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 00007f05bda15fa0 RCX: 00007f05bd79c819
RDX: 0000200000002080 RSI: 0000000000000004 RDI: 0000000000000005
RBP: 00007f05bd832c91 R08: 0000000000000000 R09: 0000000000000000
R10: 000000000000023b R11: 0000000000000246 R12: 0000000000000000
R13: 00007f05bda15fac R14: 00007f05bda15fa0 R15: 00007f05bda15fa0
 </TASK>

The buggy address belongs to a 8-page vmalloc region starting at 0xffffc90005d30000 allocated at copy_process+0x5fa/0x4030 kernel/fork.c:2186
The buggy address belongs to the physical page:
page:ffffea0000bc4c00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2f130
memcg:ffff88814338fa82
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 0000000000000000 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff ffff88814338fa82
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x102dc2(GFP_HIGHUSER|__GFP_NOWARN|__GFP_ZERO), pid 2, tgid 2 (kthreadd), ts 142565482694, free_ts 141567530433
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x173/0x1a0 mm/page_alloc.c:2559
 prep_new_page mm/page_alloc.c:2566 [inline]
 get_page_from_freelist+0x1a1e/0x1ab0 mm/page_alloc.c:4357
 __alloc_pages+0x1ec/0x4f0 mm/page_alloc.c:5657
 vm_area_alloc_pages mm/vmalloc.c:3002 [inline]
 __vmalloc_area_node mm/vmalloc.c:3071 [inline]
 __vmalloc_node_range+0x944/0x13b0 mm/vmalloc.c:3243
 alloc_thread_stack_node kernel/fork.c:312 [inline]
 dup_task_struct+0x3d3/0x6b0 kernel/fork.c:994
 copy_process+0x5fa/0x4030 kernel/fork.c:2186
 kernel_clone+0x24b/0x900 kernel/fork.c:2762
 kernel_thread+0x118/0x180 kernel/fork.c:2822
 create_kthread kernel/kthread.c:399 [inline]
 kthreadd+0x555/0x700 kernel/kthread.c:748
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1486 [inline]
 free_pcp_prepare mm/page_alloc.c:1536 [inline]
 free_unref_page_prepare+0x8b4/0x9a0 mm/page_alloc.c:3413
 free_unref_page_list+0xbb/0x8e0 mm/page_alloc.c:3554
 release_pages+0x1fa6/0x2220 mm/swap.c:1035
 __pagevec_release+0x6d/0xe0 mm/swap.c:1055
 pagevec_release include/linux/pagevec.h:71 [inline]
 folio_batch_release include/linux/pagevec.h:135 [inline]
 invalidate_mapping_pagevec+0x5c8/0x6f0 mm/truncate.c:567
 xfs_free_buftarg+0x74/0xd0 fs/xfs/xfs_buf.c:1948
 xfs_fs_put_super+0x248/0x2d0 fs/xfs/xfs_super.c:1126
 generic_shutdown_super+0x130/0x340 fs/super.c:501
 kill_block_super+0x7c/0xe0 fs/super.c:1470
 deactivate_locked_super+0x93/0xf0 fs/super.c:332
 cleanup_mnt+0x42c/0x4b0 fs/namespace.c:1191
 task_work_run+0x1d0/0x260 kernel/task_work.c:203
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82

Memory state around the buggy address:
 ffffc90005d37800: 00 00 00 00 00 00 00 00 f1 f1 f1 f1 f8 f8 f8 f8
 ffffc90005d37880: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
>ffffc90005d37900: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f3 f3 f3 f3
                                                    ^
 ffffc90005d37980: f3 f3 f3 f3 00 00 00 00 00 00 00 00 00 00 00 00
 ffffc90005d37a00: 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00 00 f3 f3
==================================================================

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/04/05 16:42 linux-6.1.y 1989cd3d56e2 4440e7c2 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro (corrupt fs)] ci2-linux-6-1-kasan KASAN: vmalloc-out-of-bounds Read in xfs_buf_lock
2026/02/01 05:42 linux-6.1.y cd9b81672742 6b8752f2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: vmalloc-out-of-bounds Read in xfs_buf_lock
2026/05/26 13:16 linux-6.1.y dcbcab9d7079 a3e47276 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: vmalloc-out-of-bounds Read in xfs_buf_lock
* Struck through repros no longer work on HEAD.