Re: [syzbot] [lsm?] KASAN: slab-use-after-free Read in security_inode_follow_link

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: slab-use-after-free Read in current_time

==================================================================
BUG: KASAN: slab-use-after-free in is_mgtime include/linux/fs.h:2313 [inline]
BUG: KASAN: slab-use-after-free in current_time+0x354/0x3b0 fs/inode.c:2378
Read of size 2 at addr ffff88803ce00e42 by task syz.0.95/6624

CPU: 1 UID: 0 PID: 6624 Comm: syz.0.95 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/0x1d0 mm/kasan/report.c:595
 is_mgtime include/linux/fs.h:2313 [inline]
 current_time+0x354/0x3b0 fs/inode.c:2378
 atime_needs_update+0x33f/0x6b0 fs/inode.c:2236
 pick_link+0x3b0/0x13c0 fs/namei.c:2040
 step_into_slowpath+0x9ba/0xf90 fs/namei.c:2123
 step_into fs/namei.c:2148 [inline]
 walk_component fs/namei.c:2284 [inline]
 link_path_walk+0xf28/0x1cc0 fs/namei.c:2652
 path_parentat fs/namei.c:2856 [inline]
 __filename_parentat+0x213/0x740 fs/namei.c:2880
 filename_parentat fs/namei.c:2898 [inline]
 filename_unlinkat+0xf4/0x6c0 fs/namei.c:5537
 __do_sys_unlinkat fs/namei.c:5595 [inline]
 __se_sys_unlinkat fs/namei.c:5587 [inline]
 __x64_sys_unlinkat+0xc0/0x130 fs/namei.c:5587
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fdbed79ce59
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:00007fdbecddd028 EFLAGS: 00000246 ORIG_RAX: 0000000000000107
RAX: ffffffffffffffda RBX: 00007fdbeda16090 RCX: 00007fdbed79ce59
RDX: 0000000000000000 RSI: 00002000000001c0 RDI: 0000000000000006
RBP: 00007fdbed832d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdbeda16128 R14: 00007fdbeda16090 R15: 00007ffe07026908
 </TASK>

Allocated by task 6623:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 unpoison_slab_object mm/kasan/common.c:340 [inline]
 __kasan_slab_alloc+0x89/0x90 mm/kasan/common.c:366
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4570 [inline]
 slab_alloc_node mm/slub.c:4899 [inline]
 kmem_cache_alloc_lru_noprof+0x246/0x6e0 mm/slub.c:4918
 alloc_inode+0x183/0x250 fs/inode.c:347
 new_inode+0x22/0x1c0 fs/inode.c:1179
 bpf_get_inode kernel/bpf/inode.c:117 [inline]
 bpf_get_inode kernel/bpf/inode.c:102 [inline]
 bpf_symlink+0x69/0x240 kernel/bpf/inode.c:391
 vfs_symlink fs/namei.c:5641 [inline]
 vfs_symlink+0x178/0x4d0 fs/namei.c:5620
 filename_symlinkat+0x2a6/0x560 fs/namei.c:5666
 __do_sys_symlinkat fs/namei.c:5686 [inline]
 __se_sys_symlinkat fs/namei.c:5681 [inline]
 __x64_sys_symlinkat+0x9c/0xe0 fs/namei.c:5681
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 6623:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5f/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2689 [inline]
 slab_free mm/slub.c:6251 [inline]
 kmem_cache_free+0x127/0x6c0 mm/slub.c:6378
 destroy_inode+0xcb/0x1c0 fs/inode.c:394
 evict+0x599/0xad0 fs/inode.c:865
 iput_final fs/inode.c:1960 [inline]
 iput.part.0+0x605/0xf50 fs/inode.c:2009
 iput+0x35/0x40 fs/inode.c:1975
 d_delete_notify include/linux/fsnotify.h:377 [inline]
 vfs_unlink+0x7a5/0xbd0 fs/namei.c:5513
 filename_unlinkat+0x3bf/0x6c0 fs/namei.c:5567
 __do_sys_unlinkat fs/namei.c:5595 [inline]
 __se_sys_unlinkat fs/namei.c:5587 [inline]
 __x64_sys_unlinkat+0xc0/0x130 fs/namei.c:5587
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88803ce00e40
 which belongs to the cache inode_cache of size 1088
The buggy address is located 2 bytes inside of
 freed 1088-byte region [ffff88803ce00e40, ffff88803ce01280)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x3ce00
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff88803ebf2801
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88801d6bc000 dead000000000100 dead000000000122
raw: 0000000000000000 00000008001a001a 00000000f5000000 ffff88803ebf2801
head: 00fff00000000040 ffff88801d6bc000 dead000000000100 dead000000000122
head: 0000000000000000 00000008001a001a 00000000f5000000 ffff88803ebf2801
head: 00fff00000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Reclaimable, gfp_mask 0xd20d0(__GFP_RECLAIMABLE|__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5148, tgid 5148 (udevd), ts 36588080945, free_ts 0
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1853
 prep_new_page mm/page_alloc.c:1861 [inline]
 get_page_from_freelist+0x11a6/0x3410 mm/page_alloc.c:3941
 __alloc_frozen_pages_noprof+0x27c/0x2bc0 mm/page_alloc.c:5221
 alloc_slab_page mm/slub.c:3278 [inline]
 allocate_slab mm/slub.c:3467 [inline]
 new_slab+0xa6/0x6c0 mm/slub.c:3525
 refill_objects+0x277/0x420 mm/slub.c:7272
 refill_sheaf mm/slub.c:2816 [inline]
 __pcs_replace_empty_main+0x375/0x650 mm/slub.c:4652
 alloc_from_pcs mm/slub.c:4750 [inline]
 slab_alloc_node mm/slub.c:4884 [inline]
 kmem_cache_alloc_lru_noprof+0x485/0x6e0 mm/slub.c:4918
 alloc_inode+0x183/0x250 fs/inode.c:347
 iget_locked+0x1d9/0x6d0 fs/inode.c:1474
 kernfs_get_inode+0x46/0x470 fs/kernfs/inode.c:252
 kernfs_iop_lookup+0x1a7/0x2d0 fs/kernfs/dir.c:1274
 __lookup_slow+0x251/0x460 fs/namei.c:1915
 lookup_slow+0x50/0x70 fs/namei.c:1932
 walk_component fs/namei.c:2278 [inline]
 link_path_walk+0x1377/0x1cc0 fs/namei.c:2652
 path_openat+0x1be/0x31a0 fs/namei.c:4854
 do_file_open+0x20e/0x430 fs/namei.c:4887
page_owner free stack trace missing

Memory state around the buggy address:
 ffff88803ce00d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88803ce00d80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>ffff88803ce00e00: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
                                           ^
 ffff88803ce00e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88803ce00f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


Tested on:

commit:         f5e5d350 Merge tag 'spi-fix-v7.1-rc5' of git://git.ker..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=164076ec580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8118209836970b54
dashboard link: https://syzkaller.appspot.com/bug?extid=0962e3a1af6d5e26a52c
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
patch:          https://syzkaller.appspot.com/x/patch.diff?x=10fff856580000