KASAN: slab-out-of-bounds Read in md5_block

Status: upstream: reported C repro on 2026/10/01 20:09
Subsystems: ecryptfs
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+03c68e42ce4b33f7ce9b@syzkaller.appspotmail.com
First crash: 4d03h, last: 1d02h
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
07afb42c repro-c Reproduced: ✅ ❓ KASAN: slab-out-of-bounds Read in md5_block 2026/10/01 05:08 2026/10/01 05:08 2026/10/01 06:26 38f7f0d1
5331704b assessment-security DenialOfService: ✅ Exploitable: ✅ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ❌ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KASAN: slab-out-of-bounds Read in md5_block 2026/09/30 00:00 2026/09/30 00:00 2026/09/30 01:08 69537153
▶ ▼ Discussions (2)
Title Replies (including bot) Last reply
[PATCH] ecryptfs: validate auth tok payload size 1 (1) 2026/10/01 21:39
[syzbot] [ecryptfs?] KASAN: slab-out-of-bounds Read in md5_block 0 (2) 2026/10/01 20:45
▶ ▼ Last patch testing requests (2)
Created Duration User Patch Repo Result
2026/10/01 20:45 15m adrianox@gmail.com patch upstream OK job log log
2026/10/01 06:27 14m retest repro git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 551c722f40809618230001baccf219193e22fc5a report job log log

Sample crash report:
==================================================================
BUG: KASAN: slab-out-of-bounds in md5_block+0x95/0x8d0 lib/crypto/md5.c:40
Read of size 64 at addr ffff8880310c0ce0 by task syz-executor265/6033

CPU: 1 UID: 0 PID: 6033 Comm: syz-executor265 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x13d/0x4b0 mm/kasan/report.c:482
 kasan_report+0xdf/0x1c0 mm/kasan/report.c:595
 check_region_inline mm/kasan/generic.c:186 [inline]
 kasan_check_range+0x10f/0x1e0 mm/kasan/generic.c:200
 __asan_memcpy+0x23/0x60 mm/kasan/shadow.c:105
 md5_block+0x95/0x8d0 lib/crypto/md5.c:40
 md5_blocks lib/crypto/md5.c:126 [inline]
 md5_update+0xf7/0x210 lib/crypto/md5.c:161
 md5+0xc7/0x120 lib/crypto/md5.c:202
 ecryptfs_write_tag_70_packet+0x880/0x1410 fs/ecryptfs/keystore.c:741
 ecryptfs_encrypt_filename fs/ecryptfs/crypto.c:1378 [inline]
 ecryptfs_encrypt_and_encode_filename+0x428/0xa60 fs/ecryptfs/crypto.c:1789
 ecryptfs_lookup+0x1f7/0x830 fs/ecryptfs/inode.c:402
 __lookup_slow+0x155/0x320 fs/namei.c:1919
 lookup_slow+0x50/0x70 fs/namei.c:1936
 walk_component fs/namei.c:2282 [inline]
 lookup_last fs/namei.c:2789 [inline]
 path_lookupat+0x5e8/0xc40 fs/namei.c:2813
 filename_lookup+0x202/0x590 fs/namei.c:2842
 __do_sys_chdir fs/open.c:557 [inline]
 __se_sys_chdir fs/open.c:550 [inline]
 __x64_sys_chdir+0xc8/0x280 fs/open.c:550
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f62183c3537
Code: 00 00 75 14 48 83 c4 28 5b 5d c3 0f 1f 84 00 00 00 00 00 8b 04 24 eb dc e8 c6 14 00 00 66 0f 1f 44 00 00 b8 50 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 d8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc52514f68 EFLAGS: 00000206 ORIG_RAX: 0000000000000050
RAX: ffffffffffffffda RBX: 00007f621841c0a9 RCX: 00007f62183c3537
RDX: 0000000000000000 RSI: 00007f621841e348 RDI: 00007f621841c0bd
RBP: 00007f621841c09e R08: 00007f621841e2b8 R09: 66615f7961727073
R10: 0000000000000000 R11: 0000000000000206 R12: 00007ffc52514f90
R13: 00007f621841c049 R14: 00007f621841c08f R15: 0000000000000002
 </TASK>

Allocated by task 5567:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:409 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:426
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __do_kmalloc_node mm/slub.c:5414 [inline]
 __kmalloc_flags_noprof+0x370/0x8e0 mm/slub.c:5602
 _kmalloc_flags_noprof mm/slab.h:55 [inline]
 __alloc_empty_sheaf mm/slub.c:2822 [inline]
 alloc_empty_sheaf mm/slub.c:2842 [inline]
 __pcs_replace_empty_main+0x3fa/0x650 mm/slub.c:4769
 alloc_from_pcs mm/slub.c:4850 [inline]
 slab_alloc_node mm/slub.c:4984 [inline]
 kmem_cache_alloc_noprof+0x4c4/0x6a0 mm/slub.c:5010
 __skb_ext_alloc+0x1a/0x80 net/core/skbuff.c:7152
 skb_ext_add+0x40b/0x810 net/core/skbuff.c:7256
 nf_bridge_alloc include/net/netfilter/br_netfilter.h:12 [inline]
 br_nf_pre_routing_ipv6+0xc7/0x8b0 net/bridge/br_netfilter_ipv6.c:171
 br_nf_pre_routing+0x90f/0x1560 net/bridge/br_netfilter_hooks.c:513
 nf_hook_entry_hookfn include/linux/netfilter.h:165 [inline]
 nf_hook_bridge_pre net/bridge/br_input.c:291 [inline]
 br_handle_frame+0xd59/0x1670 net/bridge/br_input.c:451
 __netif_receive_skb_core.constprop.0+0x6c5/0x3530 net/core/dev.c:6152
 __netif_receive_skb_one_core+0xb0/0x1e0 net/core/dev.c:6263
 __netif_receive_skb+0x1f/0x120 net/core/dev.c:6378
 process_backlog+0x487/0x1600 net/core/dev.c:6729
 __napi_poll.constprop.0+0xaf/0x450 net/core/dev.c:7798
 napi_poll net/core/dev.c:7861 [inline]
 net_rx_action+0xa40/0xf20 net/core/dev.c:8018
 handle_softirqs+0x1e6/0x9d0 kernel/softirq.c:645
 do_softirq kernel/softirq.c:546 [inline]
 do_softirq+0xaf/0xf0 kernel/softirq.c:533
 __local_bh_enable_ip+0xff/0x120 kernel/softirq.c:473
 local_bh_enable include/linux/bottom_half.h:33 [inline]
 rcu_read_unlock_bh include/linux/rcupdate.h:923 [inline]
 __dev_queue_xmit+0xa27/0x4970 net/core/dev.c:4961
 dev_queue_xmit include/linux/netdevice.h:3461 [inline]
 neigh_hh_output include/net/neighbour.h:544 [inline]
 neigh_output include/net/neighbour.h:558 [inline]
 ip6_finish_output2+0x102d/0x1d50 net/ipv6/ip6_output.c:138
 __ip6_finish_output+0x357/0xdf0 net/ipv6/ip6_output.c:210
 ip6_finish_output net/ipv6/ip6_output.c:221 [inline]
 NF_HOOK_COND include/linux/netfilter.h:314 [inline]
 ip6_output+0x2aa/0xa60 net/ipv6/ip6_output.c:248
 dst_output include/net/dst.h:471 [inline]
 NF_HOOK include/linux/netfilter.h:325 [inline]
 NF_HOOK.constprop.0+0x115/0x5a0 include/linux/netfilter.h:319
 mld_sendpack+0x8f7/0xec0 net/ipv6/mcast.c:1890
 mld_send_initial_cr+0x219/0x320 net/ipv6/mcast.c:2308
 ipv6_mc_dad_complete+0xa7/0x1d0 net/ipv6/mcast.c:2316
 addrconf_dad_completed+0xd91/0xff0 net/ipv6/addrconf.c:4376
 addrconf_dad_work+0x83c/0x1360 net/ipv6/addrconf.c:4304
 process_one_work+0xac7/0x1b10 kernel/workqueue.c:3396
 process_scheduled_works kernel/workqueue.c:3479 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3560
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

The buggy address belongs to the object at ffff8880310c0c00
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 224 bytes inside of
 allocated 256-byte region [ffff8880310c0c00, ffff8880310c0d00)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x310c0
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801c042b40 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801c042b40 dead000000000100 dead000000000122
head: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 00fff00000000001 ffffffffffffff81 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000002
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd2040(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 39, tgid 39 (kdevtmpfs), ts 10593768918
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1871
 prep_new_page mm/page_alloc.c:1879 [inline]
 get_page_from_freelist+0x110d/0x35d0 mm/page_alloc.c:3943
 __alloc_frozen_pages_noprof+0x2eb/0x3300 mm/page_alloc.c:5436
 alloc_slab_page mm/slub.c:3347 [inline]
 allocate_slab mm/slub.c:3462 [inline]
 new_slab+0xa9/0x6e0 mm/slub.c:3513
 refill_objects+0xe3/0x410 mm/slub.c:7417
 refill_sheaf mm/slub.c:2885 [inline]
 __pcs_replace_empty_main+0x35e/0x650 mm/slub.c:4774
 alloc_from_pcs mm/slub.c:4850 [inline]
 slab_alloc_node mm/slub.c:4984 [inline]
 __do_kmalloc_node mm/slub.c:5413 [inline]
 __kmalloc_noprof+0x67c/0x840 mm/slub.c:5439
 _kmalloc_noprof include/linux/slab.h:995 [inline]
 _kmalloc_array_noprof include/linux/slab.h:1211 [inline]
 security_inode_init_security+0x113/0x370 security/security.c:1347
 shmem_mknod+0x2ce/0x480 mm/shmem.c:3841
 vfs_mknod+0x3a5/0x7f0 fs/namei.c:5269
 handle_create drivers/base/devtmpfs.c:232 [inline]
 handle drivers/base/devtmpfs.c:384 [inline]
 devtmpfs_work_loop+0x48d/0xae4 drivers/base/devtmpfs.c:399
 devtmpfsd+0x3f/0x50 drivers/base/devtmpfs.c:441
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
page_owner free stack trace missing

Memory state around the buggy address:
 ffff8880310c0c00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8880310c0c80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8880310c0d00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                   ^
 ffff8880310c0d80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880310c0e00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================

Crashes (9):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/01 06:42 git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 551c722f4080 15fb8e5e .config console log report C ci-qemu-upstream KASAN: slab-out-of-bounds Read in md5_block
2026/09/30 21:39 upstream 551c722f4080 15fb8e5e .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: slab-out-of-bounds Read in md5_block
2026/09/30 16:10 upstream 551c722f4080 7808aef4 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: slab-out-of-bounds Read in md5_block
2026/09/30 14:45 upstream 551c722f4080 7808aef4 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: slab-out-of-bounds Read in md5_block
2026/09/30 09:26 upstream 551c722f4080 7808aef4 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: slab-out-of-bounds Read in md5_block
2026/09/30 04:06 upstream 6f8319e3e9a4 328436b3 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: slab-out-of-bounds Read in md5_block
2026/09/30 04:06 upstream 6f8319e3e9a4 328436b3 .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: slab-out-of-bounds Read in md5_block
2026/09/28 05:42 upstream d266640c6c76 a3c7249d .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream KASAN: slab-out-of-bounds Read in md5_block
2026/09/30 21:34 upstream 551c722f4080 15fb8e5e .config console log report info [disk image (non-bootable)] [vmlinux] [kernel image] ci-qemu-upstream-386 KASAN: slab-out-of-bounds Read in md5_block
* Struck through repros no longer work on HEAD.