[syzbot] [fuse?] KASAN: slab-use-after-free Read in fuse_test_super

[syzbot] [fuse?] KASAN: slab-use-after-free Read in fuse_test_super

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    28c736b0e92e Add linux-next specific files for 20230822
git tree:       linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=11bfe65ba80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=20999f779fa96017
dashboard link: https://syzkaller.appspot.com/bug?extid=5b64180f8d9e39d3f061
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=17c50b07a80000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=156fc5cfa80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/37bc881cd0b2/disk-28c736b0.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4512f7892b3d/vmlinux-28c736b0.xz
kernel image: https://storage.googleapis.com/syzbot-assets/052fe1287e05/bzImage-28c736b0.xz

The issue was bisected to:

commit 2c18a63b760a0f68f14cb8bb4c3840bb0b63b73e
Author: Christian Brauner <brauner@kernel.org>
Date:   Fri Aug 18 14:00:51 2023 +0000

    super: wait until we passed kill super

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=154bc0d3a80000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=174bc0d3a80000
console output: https://syzkaller.appspot.com/x/log.txt?x=134bc0d3a80000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5b64180f8d9e39d3f061@syzkaller.appspotmail.com
Fixes: 2c18a63b760a ("super: wait until we passed kill super")

==================================================================
BUG: KASAN: slab-use-after-free in get_fuse_conn_super fs/fuse/fuse_i.h:885 [inline]
BUG: KASAN: slab-use-after-free in fuse_test_super+0x8c/0xa0 fs/fuse/inode.c:1689
Read of size 8 at addr ffff88814b51bc40 by task syz-executor382/5079

CPU: 0 PID: 5079 Comm: syz-executor382 Not tainted 6.5.0-rc7-next-20230822-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
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:364 [inline]
 print_report+0xc4/0x620 mm/kasan/report.c:475
 kasan_report+0xda/0x110 mm/kasan/report.c:588
 get_fuse_conn_super fs/fuse/fuse_i.h:885 [inline]
 fuse_test_super+0x8c/0xa0 fs/fuse/inode.c:1689
 sget_fc+0x582/0x9b0 fs/super.c:778
 fuse_get_tree+0x39a/0x640 fs/fuse/inode.c:1738
 vfs_get_tree+0x8c/0x370 fs/super.c:1713
 do_new_mount fs/namespace.c:3335 [inline]
 path_mount+0x1492/0x1ed0 fs/namespace.c:3662
 do_mount fs/namespace.c:3675 [inline]
 __do_sys_mount fs/namespace.c:3884 [inline]
 __se_sys_mount fs/namespace.c:3861 [inline]
 __x64_sys_mount+0x293/0x310 fs/namespace.c:3861
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f65faa253ea
Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 5e 04 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 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:00007fff5d8df618 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fff5d8df640 RCX: 00007f65faa253ea
RDX: 0000000020000280 RSI: 0000000020000300 RDI: 0000000000000000
RBP: 0000000020000280 R08: 00007fff5d8df640 R09: 00007fff5d8df507
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000020000300
R13: 0000000000000000 R14: 00000000200028c0 R15: 00007f65faa6d06a
 </TASK>

Allocated by task 5081:
 kasan_save_stack+0x33/0x50 mm/kasan/common.c:45
 kasan_set_track+0x25/0x30 mm/kasan/common.c:52
 ____kasan_kmalloc mm/kasan/common.c:374 [inline]
 __kasan_kmalloc+0xa2/0xb0 mm/kasan/common.c:383
 kmalloc include/linux/slab.h:599 [inline]
 kzalloc include/linux/slab.h:720 [inline]
 fuse_get_tree+0xbe/0x640 fs/fuse/inode.c:1705
 vfs_get_tree+0x8c/0x370 fs/super.c:1713
 do_new_mount fs/namespace.c:3335 [inline]
 path_mount+0x1492/0x1ed0 fs/namespace.c:3662
 do_mount fs/namespace.c:3675 [inline]
 __do_sys_mount fs/namespace.c:3884 [inline]
 __se_sys_mount fs/namespace.c:3861 [inline]
 __x64_sys_mount+0x293/0x310 fs/namespace.c:3861
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Freed by task 5081:
 kasan_save_stack+0x33/0x50 mm/kasan/common.c:45
 kasan_set_track+0x25/0x30 mm/kasan/common.c:52
 kasan_save_free_info+0x2b/0x40 mm/kasan/generic.c:522
 ____kasan_slab_free mm/kasan/common.c:236 [inline]
 ____kasan_slab_free+0x15b/0x1b0 mm/kasan/common.c:200
 kasan_slab_free include/linux/kasan.h:164 [inline]
 slab_free_hook mm/slub.c:1800 [inline]
 slab_free_freelist_hook+0x114/0x1e0 mm/slub.c:1826
 slab_free mm/slub.c:3809 [inline]
 __kmem_cache_free+0xb8/0x2f0 mm/slub.c:3822
 deactivate_locked_super+0xa0/0x2d0 fs/super.c:454
 deactivate_super+0xde/0x100 fs/super.c:504
 cleanup_mnt+0x222/0x3d0 fs/namespace.c:1254
 task_work_run+0x14d/0x240 kernel/task_work.c:179
 ptrace_notify+0x10c/0x130 kernel/signal.c:2387
 ptrace_report_syscall include/linux/ptrace.h:411 [inline]
 ptrace_report_syscall_exit include/linux/ptrace.h:473 [inline]
 syscall_exit_work kernel/entry/common.c:252 [inline]
 syscall_exit_to_user_mode_prepare+0x120/0x220 kernel/entry/common.c:279
 __syscall_exit_to_user_mode_work kernel/entry/common.c:284 [inline]
 syscall_exit_to_user_mode+0xd/0x60 kernel/entry/common.c:297
 do_syscall_64+0x44/0xb0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

The buggy address belongs to the object at ffff88814b51bc40
 which belongs to the cache kmalloc-32 of size 32
The buggy address is located 0 bytes inside of
 freed 32-byte region [ffff88814b51bc40, ffff88814b51bc60)

The buggy address belongs to the physical page:
page:ffffea00052d46c0 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x14b51b
ksm flags: 0x57ff00000000800(slab|node=1|zone=2|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 057ff00000000800 ffff888012c41500 ffffea000501e700 dead000000000003
raw: 0000000000000000 0000000000400040 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 1, tgid 1 (swapper/0), ts 23776999617, free_ts 0
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x2cf/0x340 mm/page_alloc.c:1530
 prep_new_page mm/page_alloc.c:1537 [inline]
 get_page_from_freelist+0x10d7/0x31b0 mm/page_alloc.c:3213
 __alloc_pages+0x1d0/0x4a0 mm/page_alloc.c:4469
 alloc_page_interleave+0x1e/0x250 mm/mempolicy.c:2131
 alloc_pages+0x22a/0x270 mm/mempolicy.c:2293
 alloc_slab_page mm/slub.c:1870 [inline]
 allocate_slab+0x251/0x380 mm/slub.c:2017
 new_slab mm/slub.c:2070 [inline]
 ___slab_alloc+0x8be/0x1570 mm/slub.c:3223
 __slab_alloc.constprop.0+0x56/0xa0 mm/slub.c:3322
 __slab_alloc_node mm/slub.c:3375 [inline]
 slab_alloc_node mm/slub.c:3468 [inline]
 __kmem_cache_alloc_node+0x137/0x350 mm/slub.c:3517
 __do_kmalloc_node mm/slab_common.c:1022 [inline]
 __kmalloc+0x4f/0x100 mm/slab_common.c:1036
 kmalloc include/linux/slab.h:603 [inline]
 kzalloc include/linux/slab.h:720 [inline]
 kobject_get_path+0xce/0x2b0 lib/kobject.c:161
 kobject_uevent_env+0x26b/0x1800 lib/kobject_uevent.c:529
 kernel_add_sysfs_param kernel/params.c:817 [inline]
 param_sysfs_builtin kernel/params.c:852 [inline]
 param_sysfs_builtin_init+0x327/0x450 kernel/params.c:986
 do_one_initcall+0x117/0x630 init/main.c:1232
 do_initcall_level init/main.c:1294 [inline]
 do_initcalls init/main.c:1310 [inline]
 do_basic_setup init/main.c:1329 [inline]
 kernel_init_freeable+0x5c2/0x900 init/main.c:1547
 kernel_init+0x1c/0x2a0 init/main.c:1437
page_owner free stack trace missing

Memory state around the buggy address:
 ffff88814b51bb00: 00 00 05 fc fc fc fc fc fa fb fb fb fc fc fc fc
 ffff88814b51bb80: 00 00 00 00 fc fc fc fc fa fb fb fb fc fc fc fc
>ffff88814b51bc00: fa fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc
                                           ^
 ffff88814b51bc80: fa fb fb fb fc fc fc fc fa fb fb fb fc fc fc fc
 ffff88814b51bd00: fa fb fb fb fc fc fc fc 00 00 00 00 fc fc fc fc
==================================================================


---
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If the bug is already fixed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
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Re: [syzbot] [fuse?] KASAN: slab-use-after-free Read in fuse_test_super

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+5b64180f8d9e39d3f061@syzkaller.appspotmail.com

Tested on:

commit:         2ee82481 Add linux-next specific files for 20230828
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=15d40cdba80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e82a7781f9208c0d
dashboard link: https://syzkaller.appspot.com/bug?extid=5b64180f8d9e39d3f061
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=11718c2fa80000

Note: testing is done by a robot and is best-effort only.

Re: [syzbot] [fuse?] KASAN: slab-use-after-free Read in fuse_test_super

[syzbot]

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

failed to checkout kernel repo https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git on commit 28c736b0e92e: failed to run ["git" "fetch" "--force" "--tags" "fc608f7504e8b3e110eb6e7b798cef357818c5e1"]: exit status 1
error: cannot lock ref 'refs/tags/v6.5': 'refs/tags/v6.5/vfs.fixes' exists; cannot create 'refs/tags/v6.5'
From https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next
 ! [new tag]                   v6.5       -> v6.5  (unable to update local ref)
error: some local refs could not be updated; try running
 'git remote prune fc608f7504e8b3e110eb6e7b798cef357818c5e1' to remove any old, conflicting branches



Tested on:

commit:         [unknown 
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git 28c736b0e92e
kernel config:  https://syzkaller.appspot.com/x/.config?x=20999f779fa96017
dashboard link: https://syzkaller.appspot.com/bug?extid=5b64180f8d9e39d3f061
compiler:       
patch:          https://syzkaller.appspot.com/x/patch.diff?x=13359beba80000