[syzbot] [v9fs?] KASAN: slab-use-after-free Read in v9fs_stat2inode_dotl

syzbot
2024-02-02T04:49:29Z

Hello,

syzbot found the following issue on:

HEAD commit: 596764183be8 Add linux-next specific files for 20240129
git tree: linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1612e22fe80000
kernel config: https://syzkaller.appspot.com/x/.config?x=584144ad19f381aa
dashboard link: https://syzkaller.appspot.com/bug?extid=7a3d75905ea1a830dbe5
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12251228180000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1641bcdfe80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b647c038857b/disk-59676418.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/729e26c3ac55/vmlinux-59676418.xz
kernel image: https://storage.googleapis.com/syzbot-assets/15aa5e287059/bzImage-59676418.xz

The issue was bisected to:

commit 724a08450f74b02bd89078a596fd24857827c012
Author: Eric Van Hensbergen <ericvh@kernel.org>
Date: Fri Jan 5 22:25:39 2024 +0000

fs/9p: simplify iget to remove unnecessary paths

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=165c6d0fe80000
final oops: https://syzkaller.appspot.com/x/report.txt?x=155c6d0fe80000
console output: https://syzkaller.appspot.com/x/log.txt?x=115c6d0fe80000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7a3d75905ea1a830dbe5@syzkaller.appspotmail.com
Fixes: 724a08450f74 ("fs/9p: simplify iget to remove unnecessary paths")

==================================================================
BUG: KASAN: slab-use-after-free in v9fs_stat2inode_dotl+0xb3f/0xce0 fs/9p/vfs_inode_dotl.c:569
Read of size 8 at addr ffff8880172d4bb0 by task syz-executor117/5063

CPU: 1 PID: 5063 Comm: syz-executor117 Not tainted 6.8.0-rc1-next-20240129-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:377 [inline]
print_report+0xc3/0x620 mm/kasan/report.c:488
kasan_report+0xd9/0x110 mm/kasan/report.c:601
v9fs_stat2inode_dotl+0xb3f/0xce0 fs/9p/vfs_inode_dotl.c:569
v9fs_fid_iget_dotl+0x1cb/0x260 fs/9p/vfs_inode_dotl.c:85
v9fs_get_inode_from_fid fs/9p/v9fs.h:230 [inline]
v9fs_mount+0x515/0xa90 fs/9p/vfs_super.c:142
legacy_get_tree+0x109/0x220 fs/fs_context.c:662
vfs_get_tree+0x8f/0x380 fs/super.c:1784
do_new_mount fs/namespace.c:3352 [inline]
path_mount+0x14e6/0x1f20 fs/namespace.c:3679
do_mount fs/namespace.c:3692 [inline]
__do_sys_mount fs/namespace.c:3898 [inline]
__se_sys_mount fs/namespace.c:3875 [inline]
__x64_sys_mount+0x297/0x320 fs/namespace.c:3875
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xd2/0x260 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x6d/0x75
RIP: 0033:0x7f88a76d7b69
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:00007fff734da2a8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f88a76d7b69
RDX: 0000000020004500 RSI: 00000000200002c0 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000020000300 R09: 00007fff734da2e0
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fff734da2e0
R13: 00007fff734da568 R14: 431bde82d7b634db R15: 00007f88a7720074
</TASK>

Allocated by task 5063:
kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
kasan_save_track+0x14/0x30 mm/kasan/common.c:68
poison_kmalloc_redzone mm/kasan/common.c:372 [inline]
__kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:389
kmalloc include/linux/slab.h:590 [inline]
p9_client_getattr_dotl+0x4c/0x1e0 net/9p/client.c:1726
v9fs_fid_iget_dotl+0xe7/0x260 fs/9p/vfs_inode_dotl.c:73
v9fs_get_inode_from_fid fs/9p/v9fs.h:230 [inline]
v9fs_mount+0x515/0xa90 fs/9p/vfs_super.c:142
legacy_get_tree+0x109/0x220 fs/fs_context.c:662
vfs_get_tree+0x8f/0x380 fs/super.c:1784
do_new_mount fs/namespace.c:3352 [inline]
path_mount+0x14e6/0x1f20 fs/namespace.c:3679
do_mount fs/namespace.c:3692 [inline]
__do_sys_mount fs/namespace.c:3898 [inline]
__se_sys_mount fs/namespace.c:3875 [inline]
__x64_sys_mount+0x297/0x320 fs/namespace.c:3875
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xd2/0x260 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x6d/0x75

Freed by task 5063:
kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
kasan_save_track+0x14/0x30 mm/kasan/common.c:68
kasan_save_free_info+0x3f/0x60 mm/kasan/generic.c:640
poison_slab_object mm/kasan/common.c:241 [inline]
__kasan_slab_free+0x121/0x1c0 mm/kasan/common.c:257
kasan_slab_free include/linux/kasan.h:184 [inline]
slab_free_hook mm/slub.c:2122 [inline]
slab_free mm/slub.c:4296 [inline]
kfree+0x129/0x370 mm/slub.c:4406
v9fs_fid_iget_dotl+0x195/0x260 fs/9p/vfs_inode_dotl.c:81
v9fs_get_inode_from_fid fs/9p/v9fs.h:230 [inline]
v9fs_mount+0x515/0xa90 fs/9p/vfs_super.c:142
legacy_get_tree+0x109/0x220 fs/fs_context.c:662
vfs_get_tree+0x8f/0x380 fs/super.c:1784
do_new_mount fs/namespace.c:3352 [inline]
path_mount+0x14e6/0x1f20 fs/namespace.c:3679
do_mount fs/namespace.c:3692 [inline]
__do_sys_mount fs/namespace.c:3898 [inline]
__se_sys_mount fs/namespace.c:3875 [inline]
__x64_sys_mount+0x297/0x320 fs/namespace.c:3875
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xd2/0x260 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x6d/0x75

The buggy address belongs to the object at ffff8880172d4bb0
which belongs to the cache kmalloc-192 of size 192
The buggy address is located 0 bytes inside of
freed 192-byte region [ffff8880172d4bb0, ffff8880172d4c70)

The buggy address belongs to the physical page:
page:ffffea00005cb500 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x172d4
flags: 0xfff80000000800(slab|node=0|zone=1|lastcpupid=0xfff)
page_type: 0xffffffff()
raw: 00fff80000000800 ffff888014c41a00 ffffea00005fa5c0 dead000000000004
raw: 0000000000000000 00000000800f000f 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 7, tgid 7 (kworker/0:0), ts 3076962571, free_ts 0
set_page_owner include/linux/page_owner.h:31 [inline]
post_alloc_hook+0x2d4/0x350 mm/page_alloc.c:1539
prep_new_page mm/page_alloc.c:1546 [inline]
get_page_from_freelist+0xa19/0x3740 mm/page_alloc.c:3353
__alloc_pages+0x22e/0x2420 mm/page_alloc.c:4609
__alloc_pages_node include/linux/gfp.h:238 [inline]
alloc_pages_node include/linux/gfp.h:261 [inline]
alloc_slab_page mm/slub.c:2191 [inline]
allocate_slab mm/slub.c:2354 [inline]
new_slab+0xcc/0x3a0 mm/slub.c:2407
___slab_alloc+0x66d/0x17a0 mm/slub.c:3541
__slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3626
__slab_alloc_node mm/slub.c:3679 [inline]
slab_alloc_node mm/slub.c:3851 [inline]
kmalloc_node_trace+0x113/0x390 mm/slub.c:4021
kmalloc_node include/linux/slab.h:606 [inline]
kzalloc_node include/linux/slab.h:722 [inline]
alloc_worker+0x40/0x1b0 kernel/workqueue.c:2078
create_worker+0xf3/0x730 kernel/workqueue.c:2186
maybe_create_worker kernel/workqueue.c:2468 [inline]
manage_workers kernel/workqueue.c:2520 [inline]
worker_thread+0xca1/0x1290 kernel/workqueue.c:2766
kthread+0x2c1/0x3a0 kernel/kthread.c:388
ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:242
page_owner free stack trace missing

Memory state around the buggy address:
ffff8880172d4a80: fc fc fc fc fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880172d4b00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc
>ffff8880172d4b80: fc fc fc fc fc fc fa fb fb fb fb fb fb fb fb fb
^
ffff8880172d4c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc
ffff8880172d4c80: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
==================================================================

---
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