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KASAN: slab-out-of-bounds Read in ext4_search_dir

Status: upstream: reported C repro on 2023/11/17 09:38
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+99d2da6cceaf1c89cfd2@syzkaller.appspotmail.com
First crash: 169d, last: 2d10h
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2023/11/17 lts (merge base) 12952a23a5da C [report] KASAN: use-after-free Read in ext4_search_dir
2023/11/17 upstream (ToT) 7475e51b8796 C [report] KASAN: slab-use-after-free Read in ext4_search_dir
▶ ▼ Similar bugs (6)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: use-after-free Read in ext4_search_dir prio:low ext4 C error done 20 118d 359d 26/26 fixed on 2024/02/21 18:23
android-5-10 KASAN: slab-out-of-bounds Read in ext4_search_dir C 2 5d20h 169d 0/2 upstream: reported C repro on 2023/11/17 09:38
linux-5.15 KASAN: use-after-free Read in ext4_search_dir origin:upstream C 1 21d 323d 0/3 upstream: reported C repro on 2023/06/16 15:52
android-54 KASAN: use-after-free Read in ext4_search_dir C 9 5d01h 19d 0/2 upstream: reported C repro on 2024/04/15 06:47
android-6-1 KASAN: use-after-free Read in ext4_search_dir origin:upstream C error 3 5d18h 195d 0/2 upstream: reported C repro on 2023/10/22 16:55
linux-6.1 KASAN: use-after-free Read in ext4_search_dir origin:upstream C 1 17d 321d 0/3 upstream: reported C repro on 2023/06/18 19:29
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2023/12/01 09:51 5m retest repro android13-5.15-lts report log
▶ ▼ Fix bisection attempts (4)
Created Duration User Patch Repo Result
2024/04/10 11:27 2h44m bisect fix android13-5.15-lts job log (0) log
2024/03/09 16:28 37m bisect fix android13-5.15-lts job log (0) log
2024/02/03 15:20 1h12m (2) bisect fix android13-5.15-lts job log (0) log
2023/12/31 15:46 36m bisect fix android13-5.15-lts job log (0) log

Sample crash report:
==================================================================
BUG: KASAN: slab-out-of-bounds in ext4_search_dir+0xf7/0x1b0 fs/ext4/namei.c:1543
Read of size 1 at addr ffff88811d344d23 by task syz-executor249/296

CPU: 0 PID: 296 Comm: syz-executor249 Not tainted 5.15.137-syzkaller-01792-g61cfd264993d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x151/0x1b7 lib/dump_stack.c:106
 print_address_description+0x87/0x3b0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:427 [inline]
 kasan_report+0x179/0x1c0 mm/kasan/report.c:444
 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report_generic.c:306
 ext4_search_dir+0xf7/0x1b0 fs/ext4/namei.c:1543
 ext4_find_inline_entry+0x4b6/0x5e0 fs/ext4/inline.c:1714
 __ext4_find_entry+0x2b0/0x1af0 fs/ext4/namei.c:1616
 ext4_lookup_entry fs/ext4/namei.c:1771 [inline]
 ext4_lookup+0x3c6/0xaa0 fs/ext4/namei.c:1839
 __lookup_hash+0x143/0x290 fs/namei.c:1560
 filename_create+0x288/0x520 fs/namei.c:3766
 do_mkdirat+0xbd/0x450 fs/namei.c:4009
 __do_sys_mkdirat fs/namei.c:4034 [inline]
 __se_sys_mkdirat fs/namei.c:4032 [inline]
 __x64_sys_mkdirat+0x89/0xa0 fs/namei.c:4032
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f010afcec59
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 17 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffd90ff64a8 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f010afcec59
RDX: 0000000000000000 RSI: 0000000020000040 RDI: 00000000ffffff9c
RBP: 0000000000000000 R08: 00000000000014ef R09: 00007ffd90ff64e0
R10: 00000000000014f3 R11: 0000000000000246 R12: 00007ffd90ff64e0
R13: 00007ffd90ff6768 R14: 431bde82d7b634db R15: 00007f010b01703b
 </TASK>

Allocated by task 296:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:433 [inline]
 __kasan_slab_alloc+0xb1/0xe0 mm/kasan/common.c:466
 kasan_slab_alloc include/linux/kasan.h:217 [inline]
 slab_post_alloc_hook+0x53/0x2c0 mm/slab.h:550
 slab_alloc_node mm/slub.c:3240 [inline]
 slab_alloc mm/slub.c:3248 [inline]
 kmem_cache_alloc+0xf5/0x200 mm/slub.c:3253
 kmem_cache_zalloc include/linux/slab.h:723 [inline]
 __kernfs_new_node+0xdb/0x700 fs/kernfs/dir.c:593
 kernfs_new_node+0x97/0x170 fs/kernfs/dir.c:657
 __kernfs_create_file+0x4a/0x270 fs/kernfs/file.c:985
 sysfs_add_file_mode_ns+0x273/0x320 fs/sysfs/file.c:317
 create_files fs/sysfs/group.c:64 [inline]
 internal_create_group+0x573/0xf00 fs/sysfs/group.c:149
 internal_create_groups fs/sysfs/group.c:189 [inline]
 sysfs_create_groups+0x5b/0x130 fs/sysfs/group.c:215
 create_dir lib/kobject.c:100 [inline]
 kobject_add_internal+0x8ce/0xd90 lib/kobject.c:263
 kobject_add_varg lib/kobject.c:398 [inline]
 kobject_init_and_add+0x120/0x190 lib/kobject.c:481
 ext4_register_sysfs+0xbf/0x2c0 fs/ext4/sysfs.c:529
 ext4_fill_super+0x8a31/0x96e0 fs/ext4/super.c:4940
 mount_bdev+0x282/0x3b0 fs/super.c:1387
 ext4_mount+0x34/0x40 fs/ext4/super.c:6581
 legacy_get_tree+0xf1/0x190 fs/fs_context.c:611
 vfs_get_tree+0x88/0x290 fs/super.c:1517
 do_new_mount+0x28b/0xad0 fs/namespace.c:2994
 path_mount+0x671/0x1070 fs/namespace.c:3324
 do_mount fs/namespace.c:3337 [inline]
 __do_sys_mount fs/namespace.c:3545 [inline]
 __se_sys_mount+0x2c4/0x3b0 fs/namespace.c:3522
 __x64_sys_mount+0xbf/0xd0 fs/namespace.c:3522
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

The buggy address belongs to the object at ffff88811d344c80
 which belongs to the cache kernfs_node_cache of size 136
The buggy address is located 27 bytes to the right of
 136-byte region [ffff88811d344c80, ffff88811d344d08)
The buggy address belongs to the page:
page:ffffea000474d100 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x11d344
flags: 0x4000000000000200(slab|zone=1)
raw: 4000000000000200 0000000000000000 dead000000000122 ffff8881001bed80
raw: 0000000000000000 0000000000140014 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 296, ts 31140690675, free_ts 0
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1a3/0x1b0 mm/page_alloc.c:2602
 prep_new_page+0x1b/0x110 mm/page_alloc.c:2608
 get_page_from_freelist+0x3550/0x35d0 mm/page_alloc.c:4482
 __alloc_pages+0x206/0x5e0 mm/page_alloc.c:5773
 allocate_slab mm/slub.c:1932 [inline]
 new_slab+0x9a/0x4e0 mm/slub.c:1995
 ___slab_alloc+0x39e/0x830 mm/slub.c:3028
 __slab_alloc+0x4a/0x90 mm/slub.c:3115
 slab_alloc_node mm/slub.c:3206 [inline]
 slab_alloc mm/slub.c:3248 [inline]
 kmem_cache_alloc+0x134/0x200 mm/slub.c:3253
 kmem_cache_zalloc include/linux/slab.h:723 [inline]
 __kernfs_new_node+0xdb/0x700 fs/kernfs/dir.c:593
 kernfs_new_node+0x97/0x170 fs/kernfs/dir.c:657
 __kernfs_create_file+0x4a/0x270 fs/kernfs/file.c:985
 sysfs_add_file_mode_ns+0x273/0x320 fs/sysfs/file.c:317
 create_files fs/sysfs/group.c:64 [inline]
 internal_create_group+0x573/0xf00 fs/sysfs/group.c:149
 internal_create_groups fs/sysfs/group.c:189 [inline]
 sysfs_create_groups+0x5b/0x130 fs/sysfs/group.c:215
 create_dir lib/kobject.c:100 [inline]
 kobject_add_internal+0x8ce/0xd90 lib/kobject.c:263
 kobject_add_varg lib/kobject.c:398 [inline]
 kobject_init_and_add+0x120/0x190 lib/kobject.c:481
page_owner free stack trace missing

Memory state around the buggy address:
 ffff88811d344c00: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
 ffff88811d344c80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88811d344d00: 00 fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00
                               ^
 ffff88811d344d80: 00 00 00 00 00 00 00 00 00 00 fc fc fc fc fc fc
 ffff88811d344e00: fc fc 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================
EXT4-fs error (device loop0): ext4_find_dest_de:2112: inode #12: block 7: comm syz-executor249: bad entry in directory: rec_len % 4 != 0 - offset=0, inode=3089191003, rec_len=43069, size=56 fake=0

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2023/11/17 09:36 android13-5.15-lts 61cfd264993d cb976f63 .config console log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro #1] [mounted in repro #2] ci2-android-5-15 KASAN: slab-out-of-bounds Read in ext4_search_dir
2024/05/02 19:51 android13-5.15-lts 5d96939590c0 3ba885bc .config strace log report syz C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-android-5-15 KASAN: use-after-free Read in ext4_search_dir
* Struck through repros no longer work on HEAD.