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

Status: auto-obsoleted due to no activity on 2025/05/11 23:03
Reported-by: syzbot+31c2f710e089e86b19b9@syzkaller.appspotmail.com
First crash: 552d, last: 552d
▶ ▼ Similar bugs (7)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 KASAN: slab-out-of-bounds Read in drop_buffers (2) origin:lts-only 17 syz, C inconclusive 18 120d 321d 3/3 fixed on 2026/04/11 13:11
upstream KASAN: null-ptr-deref Read in drop_buffers (5) prio:high fs 11 14 53d 269d 0/29 upstream: reported on 2025/11/10 12:38
upstream KASAN: null-ptr-deref Read in drop_buffers (2) jfs 11 syz, C error 252 890d 1101d 0/29 auto-obsoleted due to no activity on 2024/05/08 22:28
upstream KASAN: null-ptr-deref Read in drop_buffers kernfs 11 5 1377d 1377d 0/29 auto-obsoleted due to no activity on 2023/02/27 02:04
upstream KASAN: null-ptr-deref Read in drop_buffers (4) fs 17 228 345d 354d 0/29 auto-obsoleted due to no activity on 2025/10/15 13:15
linux-6.1 KASAN: null-ptr-deref Read in drop_buffers 11 1 64d 64d 0/3 upstream: reported on 2026/06/03 12:36
upstream KASAN: null-ptr-deref Read in drop_buffers (3) fs 17 syz, C 98 508d 674d 0/29 auto-obsoleted due to no activity on 2025/06/08 23:43

Sample crash report:
==================================================================
BUG: KASAN: slab-out-of-bounds in instrument_atomic_read include/linux/instrumented.h:72 [inline]
BUG: KASAN: slab-out-of-bounds in atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
BUG: KASAN: slab-out-of-bounds in buffer_busy fs/buffer.c:2784 [inline]
BUG: KASAN: slab-out-of-bounds in drop_buffers+0x6f/0x700 fs/buffer.c:2796
Read of size 4 at addr ffff88807e5e0660 by task syz.1.2988/20660

CPU: 0 PID: 20660 Comm: syz.1.2988 Not tainted 6.1.127-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2cb lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:316 [inline]
 print_report+0x15f/0x4f0 mm/kasan/report.c:427
 kasan_report+0x136/0x160 mm/kasan/report.c:531
 kasan_check_range+0x27f/0x290 mm/kasan/generic.c:189
 instrument_atomic_read include/linux/instrumented.h:72 [inline]
 atomic_read include/linux/atomic/atomic-instrumented.h:27 [inline]
 buffer_busy fs/buffer.c:2784 [inline]
 drop_buffers+0x6f/0x700 fs/buffer.c:2796
 try_to_free_buffers+0x295/0x600 fs/buffer.c:2826
 shrink_folio_list+0x288c/0x8f40 mm/vmscan.c:2003
 evict_folios+0xaf8/0x25b0 mm/vmscan.c:5046
 lru_gen_shrink_lruvec mm/vmscan.c:5229 [inline]
 shrink_lruvec+0xdbf/0x4650 mm/vmscan.c:5924
 </TASK>

Allocated by task 13123:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4b/0x70 mm/kasan/common.c:52
 ____kasan_kmalloc mm/kasan/common.c:374 [inline]
 __kasan_kmalloc+0x97/0xb0 mm/kasan/common.c:383
 kasan_kmalloc include/linux/kasan.h:211 [inline]
 __do_kmalloc_node mm/slab_common.c:936 [inline]
 __kmalloc+0xb2/0x230 mm/slab_common.c:949
 kmalloc include/linux/slab.h:568 [inline]
 kzalloc include/linux/slab.h:699 [inline]
 iomap_page_create+0x151/0x610 fs/iomap/buffered-io.c:61
 iomap_readpage_iter+0x332/0xb90 fs/iomap/buffered-io.c:273
 iomap_read_folio+0x3d2/0xa10 fs/iomap/buffered-io.c:344
 filemap_read_folio+0x199/0x780 mm/filemap.c:2489
 do_read_cache_folio+0x2ee/0x810 mm/filemap.c:3626
 erofs_bread+0x19d/0x6b0 fs/erofs/data.c:50
 erofs_find_target_block fs/erofs/namei.c:102 [inline]
 erofs_namei+0x278/0xef0 fs/erofs/namei.c:175
 erofs_lookup+0x1d6/0x4d0 fs/erofs/namei.c:204
 __lookup_slow+0x27e/0x3d0 fs/namei.c:1690
 lookup_slow+0x53/0x70 fs/namei.c:1707
 walk_component+0x2d0/0x400 fs/namei.c:1998
 lookup_last fs/namei.c:2455 [inline]
 path_lookupat+0x16f/0x450 fs/namei.c:2479
 filename_lookup+0x251/0x600 fs/namei.c:2508
 user_path_at_empty+0x3e/0x60 fs/namei.c:2905
 user_path_at include/linux/namei.h:57 [inline]
 do_mount fs/namespace.c:3396 [inline]
 __do_sys_mount fs/namespace.c:3607 [inline]
 __se_sys_mount+0x296/0x3c0 fs/namespace.c:3584
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

Last potentially related work creation:
 kasan_save_stack+0x3b/0x60 mm/kasan/common.c:45
 __kasan_record_aux_stack+0xb0/0xc0 mm/kasan/generic.c:486
 kvfree_call_rcu+0x116/0x8c0 kernel/rcu/tree.c:3401
 cfg80211_update_known_bss+0x16b/0x9e0
 cfg80211_bss_update+0x187/0x2280 net/wireless/scan.c:1817
 cfg80211_inform_single_bss_frame_data net/wireless/scan.c:2476 [inline]
 cfg80211_inform_bss_frame_data+0xae4/0x1680 net/wireless/scan.c:2509
 ieee80211_bss_info_update+0x847/0xf00 net/mac80211/scan.c:190
 ieee80211_rx_bss_info net/mac80211/ibss.c:1120 [inline]
 ieee80211_rx_mgmt_probe_beacon net/mac80211/ibss.c:1609 [inline]
 ieee80211_ibss_rx_queued_mgmt+0x1962/0x2dd0 net/mac80211/ibss.c:1638
 ieee80211_iface_process_skb net/mac80211/iface.c:1668 [inline]
 ieee80211_iface_work+0x7aa/0xce0 net/mac80211/iface.c:1722
 process_one_work+0x8a9/0x11d0 kernel/workqueue.c:2292
 worker_thread+0xa47/0x1200 kernel/workqueue.c:2439
 kthread+0x28d/0x320 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

Second to last potentially related work creation:
 kasan_save_stack+0x3b/0x60 mm/kasan/common.c:45
 __kasan_record_aux_stack+0xb0/0xc0 mm/kasan/generic.c:486
 kvfree_call_rcu+0x116/0x8c0 kernel/rcu/tree.c:3401
 cfg80211_update_known_bss+0x16b/0x9e0
 cfg80211_bss_update+0x187/0x2280 net/wireless/scan.c:1817
 cfg80211_inform_single_bss_frame_data net/wireless/scan.c:2476 [inline]
 cfg80211_inform_bss_frame_data+0xae4/0x1680 net/wireless/scan.c:2509
 ieee80211_bss_info_update+0x847/0xf00 net/mac80211/scan.c:190
 ieee80211_rx_bss_info net/mac80211/ibss.c:1120 [inline]
 ieee80211_rx_mgmt_probe_beacon net/mac80211/ibss.c:1609 [inline]
 ieee80211_ibss_rx_queued_mgmt+0x1962/0x2dd0 net/mac80211/ibss.c:1638
 ieee80211_iface_process_skb net/mac80211/iface.c:1668 [inline]
 ieee80211_iface_work+0x7aa/0xce0 net/mac80211/iface.c:1722
 process_one_work+0x8a9/0x11d0 kernel/workqueue.c:2292
 worker_thread+0xa47/0x1200 kernel/workqueue.c:2439
 kthread+0x28d/0x320 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

The buggy address belongs to the object at ffff88807e5e0600
 which belongs to the cache kmalloc-96 of size 96
The buggy address is located 0 bytes to the right of
 96-byte region [ffff88807e5e0600, ffff88807e5e0660)

The buggy address belongs to the physical page:
page:ffffea0001f97800 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88807e5e0200 pfn:0x7e5e0
flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000200 ffffea0001f82ec8 ffffea0000a5b548 ffff888017c41780
raw: ffff88807e5e0200 0000000000200019 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 0x12c40(GFP_NOFS|__GFP_NOWARN|__GFP_NORETRY), pid 3604, tgid 3604 (S01syslogd), ts 24285483800, free_ts 22684759500
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x18d/0x1b0 mm/page_alloc.c:2532
 prep_new_page mm/page_alloc.c:2539 [inline]
 get_page_from_freelist+0x3731/0x38d0 mm/page_alloc.c:4328
 __alloc_pages+0x28d/0x770 mm/page_alloc.c:5605
 alloc_slab_page+0x6a/0x150 mm/slub.c:1794
 allocate_slab mm/slub.c:1939 [inline]
 new_slab+0x84/0x2d0 mm/slub.c:1992
 ___slab_alloc+0xc20/0x1270 mm/slub.c:3180
 __slab_alloc mm/slub.c:3279 [inline]
 slab_alloc_node mm/slub.c:3364 [inline]
 __kmem_cache_alloc_node+0x19f/0x260 mm/slub.c:3437
 __do_kmalloc_node mm/slab_common.c:935 [inline]
 __kmalloc+0xa1/0x230 mm/slab_common.c:949
 kmalloc_array include/linux/slab.h:615 [inline]
 kcalloc include/linux/slab.h:646 [inline]
 ext4_find_extent+0x378/0xe20 fs/ext4/extents.c:914
 ext4_ext_map_blocks+0x309/0x7ab0 fs/ext4/extents.c:4165
 ext4_map_blocks+0x401/0x1cb0 fs/ext4/inode.c:605
 ext4_mpage_readpages+0xb82/0x2eb0 fs/ext4/readpage.c:305
 read_pages+0x17f/0x830 mm/readahead.c:161
 page_cache_ra_unbounded+0x68b/0x7b0 mm/readahead.c:270
 page_cache_sync_readahead include/linux/pagemap.h:1248 [inline]
 filemap_get_pages mm/filemap.c:2664 [inline]
 filemap_read+0x7fa/0x31d0 mm/filemap.c:2758
 __kernel_read+0x421/0x890 fs/read_write.c:428
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1459 [inline]
 free_pcp_prepare mm/page_alloc.c:1509 [inline]
 free_unref_page_prepare+0x12a6/0x15b0 mm/page_alloc.c:3384
 free_unref_page+0x33/0x3e0 mm/page_alloc.c:3479
 kasan_depopulate_vmalloc_pte+0x66/0x80 mm/kasan/shadow.c:375
 apply_to_pte_range mm/memory.c:2662 [inline]
 apply_to_pmd_range mm/memory.c:2706 [inline]
 apply_to_pud_range mm/memory.c:2742 [inline]
 apply_to_p4d_range mm/memory.c:2778 [inline]
 __apply_to_page_range+0x9c5/0xcc0 mm/memory.c:2812
 kasan_release_vmalloc+0x96/0xb0 mm/kasan/shadow.c:492
 __purge_vmap_area_lazy+0x157c/0x1720 mm/vmalloc.c:1774
 _vm_unmap_aliases+0x476/0x4e0 mm/vmalloc.c:2177
 change_page_attr_set_clr+0x304/0xe70 arch/x86/mm/pat/set_memory.c:1821
 change_page_attr_set arch/x86/mm/pat/set_memory.c:1871 [inline]
 set_memory_nx+0xee/0x130 arch/x86/mm/pat/set_memory.c:2064
 free_init_pages arch/x86/mm/init.c:933 [inline]
 free_kernel_image_pages arch/x86/mm/init.c:952 [inline]
 free_initmem+0x71/0xc0 arch/x86/mm/init.c:979
 kernel_init+0x2d/0x290 init/main.c:1523
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

Memory state around the buggy address:
 ffff88807e5e0500: 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc
 ffff88807e5e0580: 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc
>ffff88807e5e0600: 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc
                                                       ^
 ffff88807e5e0680: 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc
 ffff88807e5e0700: 00 00 00 00 00 00 00 00 00 00 00 00 fc fc fc fc
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/01/31 23:02 linux-6.1.y 75cefdf153f5 aa47157c .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: slab-out-of-bounds Read in drop_buffers
* Struck through repros no longer work on HEAD.