[syzbot] [overlayfs?] KASAN: invalid-free in ovl_copy_up_one

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 940fcc189c51 Add linux-next specific files for 20230921
git tree: linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=158b9424680000
kernel config: https://syzkaller.appspot.com/x/.config?x=1f140ae6e669ac24
dashboard link: https://syzkaller.appspot.com/bug?extid=477d8d8901756d1cbba1
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=120e0dba680000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12f3767a680000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b8921b235c24/disk-940fcc18.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c80a9f6bcdd4/vmlinux-940fcc18.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ed10a4df6950/bzImage-940fcc18.xz

The issue was bisected to:

commit 44ef23e481b02df2f17599a24f81cf0045dc5256
Author: Amir Goldstein <amir...@gmail.com>
Date: Wed Aug 16 13:47:59 2023 +0000

ovl: do not encode lower fh with upper sb_writers held

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1364cda6680000
final oops: https://syzkaller.appspot.com/x/report.txt?x=10e4cda6680000
console output: https://syzkaller.appspot.com/x/log.txt?x=1764cda6680000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+477d8d...@syzkaller.appspotmail.com
Fixes: 44ef23e481b0 ("ovl: do not encode lower fh with upper sb_writers held")

RAX: ffffffffffffffda RBX: 00007ffd8d25ca30 RCX: 00007f15a9d353e9
RDX: 00007f15a9d344b0 RSI: 00007ffd8d25ca30 RDI: 0000000020000200
RBP: 0000000000000002 R08: 00007ffd8d25c7a6 R09: 00007ffd8d2d51a0
R10: 0000000000000002 R11: 0000000000000246 R12: 00007ffd8d25ca2c
R13: 00007ffd8d25ca70 R14: 00007ffd8d25ca50 R15: 0000000000000002
</TASK>
==================================================================
BUG: KASAN: invalid-free in slab_free mm/slub.c:3809 [inline]
BUG: KASAN: invalid-free in __kmem_cache_free+0xb8/0x2d0 mm/slub.c:3822
Free of addr ffff888078b14650 by task syz-executor360/5060

CPU: 0 PID: 5060 Comm: syz-executor360 Not tainted 6.6.0-rc2-next-20230921-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/04/2023
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_invalid_free+0xab/0xd0 mm/kasan/report.c:550
____kasan_slab_free+0x1a0/0x1b0 mm/kasan/common.c:216
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+0xb8/0x2d0 mm/slub.c:3822
ovl_do_copy_up fs/overlayfs/copy_up.c:973 [inline]
ovl_copy_up_one+0x15ac/0x3250 fs/overlayfs/copy_up.c:1137
ovl_copy_up_flags+0x189/0x200 fs/overlayfs/copy_up.c:1192
ovl_nlink_start+0x391/0x470 fs/overlayfs/util.c:1144
ovl_do_remove+0x16d/0xd50 fs/overlayfs/dir.c:893
vfs_unlink+0x2f1/0x900 fs/namei.c:4313
do_unlinkat+0x3da/0x6d0 fs/namei.c:4379
__do_sys_unlink fs/namei.c:4427 [inline]
__se_sys_unlink fs/namei.c:4425 [inline]
__x64_sys_unlink+0xc8/0x110 fs/namei.c:4425
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f15a9d353e9
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:00007ffd8d25ca08 EFLAGS: 00000246 ORIG_RAX: 0000000000000057
RAX: ffffffffffffffda RBX: 00007ffd8d25ca30 RCX: 00007f15a9d353e9
RDX: 00007f15a9d344b0 RSI: 00007ffd8d25ca30 RDI: 0000000020000200
RBP: 0000000000000002 R08: 00007ffd8d25c7a6 R09: 00007ffd8d2d51a0
R10: 0000000000000002 R11: 0000000000000246 R12: 00007ffd8d25ca2c
R13: 00007ffd8d25ca70 R14: 00007ffd8d25ca50 R15: 0000000000000002
</TASK>

Allocated by task 5060:
kasan_save_stack+0x33/0x50 mm/kasan/common.c:45
kasan_set_track+0x25/0x30 mm/kasan/common.c:52
__kasan_slab_alloc+0x81/0x90 mm/kasan/common.c:328
kasan_slab_alloc include/linux/kasan.h:188 [inline]
slab_post_alloc_hook mm/slab.h:762 [inline]
slab_alloc_node mm/slub.c:3478 [inline]
slab_alloc mm/slub.c:3486 [inline]
__kmem_cache_alloc_lru mm/slub.c:3493 [inline]
kmem_cache_alloc_lru+0x215/0x670 mm/slub.c:3509
__d_alloc+0x32/0xac0 fs/dcache.c:1768
d_alloc+0x4e/0x220 fs/dcache.c:1848
lookup_one_qstr_excl+0xc7/0x180 fs/namei.c:1604
do_unlinkat+0x294/0x6d0 fs/namei.c:4365
__do_sys_unlink fs/namei.c:4427 [inline]
__se_sys_unlink fs/namei.c:4425 [inline]
__x64_sys_unlink+0xc8/0x110 fs/namei.c:4425
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x63/0xcd

Last potentially related work creation:
kasan_save_stack+0x33/0x50 mm/kasan/common.c:45
__kasan_record_aux_stack+0xbc/0xd0 mm/kasan/generic.c:492
__call_rcu_common.constprop.0+0x9a/0x790 kernel/rcu/tree.c:2653
dentry_free+0xc2/0x160 fs/dcache.c:377
__dentry_kill+0x4c1/0x640 fs/dcache.c:621
dentry_kill fs/dcache.c:745 [inline]
dput+0x6de/0xf80 fs/dcache.c:913
handle_mounts fs/namei.c:1554 [inline]
step_into+0x1192/0x2230 fs/namei.c:1839
walk_component+0xfc/0x5a0 fs/namei.c:2007
lookup_last fs/namei.c:2458 [inline]
path_lookupat+0x17f/0x770 fs/namei.c:2482
filename_lookup+0x1e7/0x5b0 fs/namei.c:2511
vfs_statx+0x160/0x430 fs/stat.c:240
vfs_fstatat+0xb3/0x140 fs/stat.c:295
__do_sys_newfstatat+0x98/0x110 fs/stat.c:459
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x63/0xcd

The buggy address belongs to the object at ffff888078b145e0
which belongs to the cache dentry of size 312
The buggy address is located 112 bytes inside of
312-byte region [ffff888078b145e0, ffff888078b14718)

The buggy address belongs to the physical page:
page:ffffea0001e2c500 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x78b14
head:ffffea0001e2c500 order:1 entire_mapcount:0 nr_pages_mapped:0 pincount:0
ksm flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff88814000a8c0 ffffea0001e2d080 dead000000000003
raw: 0000000000000000 0000000000150015 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Reclaimable, gfp_mask 0xd20d0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_RECLAIMABLE), pid 4515, tgid 4515 (udevd), ts 47959600386, free_ts 28011797989
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+0xf17/0x2e50 mm/page_alloc.c:3200
__alloc_pages+0x1d0/0x4a0 mm/page_alloc.c:4456
alloc_pages+0x1a9/0x270 mm/mempolicy.c:2305
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+0x8c7/0x1580 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]
slab_alloc mm/slub.c:3486 [inline]
__kmem_cache_alloc_lru mm/slub.c:3493 [inline]
kmem_cache_alloc_lru+0x4e1/0x670 mm/slub.c:3509
__d_alloc+0x32/0xac0 fs/dcache.c:1768
d_alloc+0x4e/0x220 fs/dcache.c:1848
d_alloc_parallel+0xe9/0x12d0 fs/dcache.c:2637
lookup_open.isra.0+0xaa4/0x13b0 fs/namei.c:3401
open_last_lookups fs/namei.c:3544 [inline]
path_openat+0x931/0x29c0 fs/namei.c:3774
do_filp_open+0x1de/0x430 fs/namei.c:3804
do_sys_openat2+0x176/0x1e0 fs/open.c:1422
do_sys_open fs/open.c:1437 [inline]
__do_sys_openat fs/open.c:1453 [inline]
__se_sys_openat fs/open.c:1448 [inline]
__x64_sys_openat+0x175/0x210 fs/open.c:1448
page last free stack trace:
reset_page_owner include/linux/page_owner.h:24 [inline]
free_pages_prepare mm/page_alloc.c:1130 [inline]
free_unref_page_prepare+0x476/0xa40 mm/page_alloc.c:2342
free_unref_page+0x33/0x3b0 mm/page_alloc.c:2435
free_contig_range+0xb6/0x190 mm/page_alloc.c:6372
destroy_args+0x7c9/0xa10 mm/debug_vm_pgtable.c:1028
debug_vm_pgtable+0x1d79/0x3e00 mm/debug_vm_pgtable.c:1408
do_one_initcall+0x11c/0x640 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+0x5c2/0x8f0 init/main.c:1547
kernel_init+0x1c/0x2a0 init/main.c:1437
ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304

Memory state around the buggy address:
ffff888078b14500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888078b14580: 00 00 00 00 fc fc fc fc fc fc fc fc 00 00 00 00
>ffff888078b14600: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
^
ffff888078b14680: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff888078b14700: 00 00 00 fc fc fc fc fc fc fc fc 00 00 00 00 00
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection

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:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite bug's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the bug is a duplicate of another bug, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[Amir Goldstein]

#syz test: https://github.com/amir73il/linux.git ovl_want_write

[syzbot]

Hello,

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

Reported-and-tested-by: syzbot+477d8d...@syzkaller.appspotmail.com

Tested on:

commit: 8e9b46c4 ovl: do not encode lower fh with upper sb_wri..
git tree: https://github.com/amir73il/linux.git ovl_want_write
console output: https://syzkaller.appspot.com/x/log.txt?x=10d10ffa680000
kernel config: https://syzkaller.appspot.com/x/.config?x=bb54ecdfa197f132

dashboard link: https://syzkaller.appspot.com/bug?extid=477d8d8901756d1cbba1
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

Note: no patches were applied.
Note: testing is done by a robot and is best-effort only.

[Jann Horn]

On Wed, Sep 27, 2023 at 5:10 PM syzbot
<syzbot+477d8d...@syzkaller.appspotmail.com> wrote:
> syzbot has tested the proposed patch and the reproducer did not trigger any issue:
>
> Reported-and-tested-by: syzbot+477d8d...@syzkaller.appspotmail.com
>
> Tested on:
>
> commit: 8e9b46c4 ovl: do not encode lower fh with upper sb_wri..
> git tree: https://github.com/amir73il/linux.git ovl_want_write
> console output: https://syzkaller.appspot.com/x/log.txt?x=10d10ffa680000
> kernel config: https://syzkaller.appspot.com/x/.config?x=bb54ecdfa197f132
> dashboard link: https://syzkaller.appspot.com/bug?extid=477d8d8901756d1cbba1
> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

It looks like the fix was submitted without the Reported-by tag, so
syzkaller doesn't recognize that the fix has landed... I'll tell
syzkaller now which commit the fix is supposed to be in, please
correct me if this is wrong:

#syz fix: ovl: do not encode lower fh with upper sb_writers held

[Jann Horn]

(Ah, and just for the record: I hadn't realized when writing this that
the fix was actually in a newer version of the same patch... "git
range-diff 44ef23e481b02df2f17599a24f81cf0045dc5256~1..44ef23e481b02df2f17599a24f81cf0045dc5256
5b02bfc1e7e3811c5bf7f0fa626a0694d0dbbd77~1..5b02bfc1e7e3811c5bf7f0fa626a0694d0dbbd77"
shows an added "ovl_get_index_name", I guess that's the fix?)

[syzbot]

> On Fri, Nov 24, 2023 at 5:26 PM Jann Horn <ja...@google.com> wrote:
>>
>> On Fri, Nov 24, 2023 at 4:11 PM Jann Horn <ja...@google.com> wrote:
>> >
>> > On Wed, Sep 27, 2023 at 5:10 PM syzbot
>> > <syzbot+477d8d...@syzkaller.appspotmail.com> wrote:
>> > > syzbot has tested the proposed patch and the reproducer did not trigger any issue:
>> > >
>> > > Reported-and-tested-by: syzbot+477d8d...@syzkaller.appspotmail.com
>> > >
>> > > Tested on:
>> > >
>> > > commit: 8e9b46c4 ovl: do not encode lower fh with upper sb_wri..
>> > > git tree: https://github.com/amir73il/linux.git ovl_want_write
>> > > console output: https://syzkaller.appspot.com/x/log.txt?x=10d10ffa680000
>> > > kernel config: https://syzkaller.appspot.com/x/.config?x=bb54ecdfa197f132
>> > > dashboard link: https://syzkaller.appspot.com/bug?extid=477d8d8901756d1cbba1
>> > > compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
>> >
>> > It looks like the fix was submitted without the Reported-by tag, so
>> > syzkaller doesn't recognize that the fix has landed... I'll tell
>> > syzkaller now which commit the fix is supposed to be in, please
>> > correct me if this is wrong:
>> >
>> > #syz fix: ovl: do not encode lower fh with upper sb_writers held
>>
>> (Ah, and just for the record: I hadn't realized when writing this that
>> the fix was actually in a newer version of the same patch... "git
>

> That is correct.
> I am very thankful for syzbot with helping me catch bugs during development
> and I would gladly attribute the bot and its owners, but I don't that
> Reported-and-tested-by is an adequate tag for a bug that never existed as
> far as git history.
>
> Even Tested-by: syzbot could be misleading to stable kernel bots
> that may conclude that the patch is a fix that needs to apply to stable.
>
> I am open to suggestions.
>
> Also maybe
>
> #syz correction:

unknown command "correction:"

>
> To tell syzbot we are not fixing a bug in upstream, but in a previous
> version of a patch that it had tested.

>
>> range-diff 44ef23e481b02df2f17599a24f81cf0045dc5256~1..44ef23e481b02df2f17599a24f81cf0045dc5256
>> 5b02bfc1e7e3811c5bf7f0fa626a0694d0dbbd77~1..5b02bfc1e7e3811c5bf7f0fa626a0694d0dbbd77"
>> shows an added "ovl_get_index_name", I guess that's the fix?)
>

> No, that added ovl_get_index_name() seems like a fluke of the range-diff tool.
> All the revisions of this patch always had this same minor change in this line:
>
> - err = ovl_get_index_name(ofs, c->lowerpath.dentry,
> &c->destname);
> + err = ovl_get_index_name(ofs, origin, &c->destname);
>
> The fix is obviously in the other part of the range-diff.
>
> Thanks,
> Amir.
>
> if (err)
> - return err;
> -+ goto out;
> ++ goto out_free_fh;
> } else if (WARN_ON(!c->parent)) {
> /* Disconnected dentry must be copied up to index dir */
> - return -EIO;
> + err = -EIO;
> -+ goto out;
> ++ goto out_free_fh;
> } else {
> /*
> * Mark parent "impure" because it may now contain non-pure
> @@ fs/overlayfs/copy_up.c: static int ovl_do_copy_up(struct
> ovl_copy_up_ctx *c)
> ovl_end_write(c->dentry);
> if (err)
> - return err;
> -+ goto out;
> ++ goto out_free_fh;
> }
>
> /* Should we copyup with O_TMPFILE or with workdir? */
> @@ fs/overlayfs/copy_up.c: static int ovl_do_copy_up(struct
> ovl_copy_up_ctx *c)
> out:
> if (to_index)
> kfree(c->destname.name);
> ++out_free_fh:
> + kfree(fh);
> return err;
> }

[Amir Goldstein]

On Fri, Nov 24, 2023 at 5:26 PM Jann Horn <ja...@google.com> wrote:
>
> On Fri, Nov 24, 2023 at 4:11 PM Jann Horn <ja...@google.com> wrote:
> >
> > On Wed, Sep 27, 2023 at 5:10 PM syzbot
> > <syzbot+477d8d...@syzkaller.appspotmail.com> wrote:
> > > syzbot has tested the proposed patch and the reproducer did not trigger any issue:
> > >
> > > Reported-and-tested-by: syzbot+477d8d...@syzkaller.appspotmail.com
> > >
> > > Tested on:
> > >
> > > commit: 8e9b46c4 ovl: do not encode lower fh with upper sb_wri..
> > > git tree: https://github.com/amir73il/linux.git ovl_want_write
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=10d10ffa680000
> > > kernel config: https://syzkaller.appspot.com/x/.config?x=bb54ecdfa197f132
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=477d8d8901756d1cbba1
> > > compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> >
> > It looks like the fix was submitted without the Reported-by tag, so
> > syzkaller doesn't recognize that the fix has landed... I'll tell
> > syzkaller now which commit the fix is supposed to be in, please
> > correct me if this is wrong:
> >
> > #syz fix: ovl: do not encode lower fh with upper sb_writers held
>
> (Ah, and just for the record: I hadn't realized when writing this that
> the fix was actually in a newer version of the same patch... "git

That is correct.
I am very thankful for syzbot with helping me catch bugs during development
and I would gladly attribute the bot and its owners, but I don't that
Reported-and-tested-by is an adequate tag for a bug that never existed as
far as git history.

Even Tested-by: syzbot could be misleading to stable kernel bots
that may conclude that the patch is a fix that needs to apply to stable.

I am open to suggestions.

Also maybe

#syz correction:

To tell syzbot we are not fixing a bug in upstream, but in a previous
version of a patch that it had tested.

> range-diff 44ef23e481b02df2f17599a24f81cf0045dc5256~1..44ef23e481b02df2f17599a24f81cf0045dc5256
> 5b02bfc1e7e3811c5bf7f0fa626a0694d0dbbd77~1..5b02bfc1e7e3811c5bf7f0fa626a0694d0dbbd77"
> shows an added "ovl_get_index_name", I guess that's the fix?)

[Jann Horn]

Sorry, I think I got that wrong; the syzbot manual
(https://github.com/google/syzkaller/blob/master/docs/syzbot.md#rebuilt-treesamended-patches)
instead suggests:

"First, adding Reported-by tags to amended commits may be misleading.
A Reported-by tag suggests that the commit fixes a bug in some
previous commit, but here it's not the case (it only fixes a bug in a
previous version of itself which is not in the tree). In such case
it's recommended to include a Tested-by or a Reviewed-by tag with the
hash instead. Technically, syzbot accepts any tag, so With-inputs-from
would work too."

> > range-diff 44ef23e481b02df2f17599a24f81cf0045dc5256~1..44ef23e481b02df2f17599a24f81cf0045dc5256
> > 5b02bfc1e7e3811c5bf7f0fa626a0694d0dbbd77~1..5b02bfc1e7e3811c5bf7f0fa626a0694d0dbbd77"
> > shows an added "ovl_get_index_name", I guess that's the fix?)
>
> No, that added ovl_get_index_name() seems like a fluke of the range-diff tool.
> All the revisions of this patch always had this same minor change in this line:

Ah, bleh, of course. I haven't used range-diff in a while and misread
the output...