[syzbot] [bluetooth?] KASAN: slab-use-after-free Read in sk_skb_reason_drop

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 84562f9953ec Merge branch '100GbE' of git://git.kernel.org..
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=10e1c2d6980000
kernel config: https://syzkaller.appspot.com/x/.config?x=e78fc116033e0ab7
dashboard link: https://syzkaller.appspot.com/bug?extid=f115fcf7e49b2ebc902d
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1075608e980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e1edb6a0d5b1/disk-84562f99.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/7df8d6218d93/vmlinux-84562f99.xz
kernel image: https://storage.googleapis.com/syzbot-assets/151998fb709d/bzImage-84562f99.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f115fc...@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in instrument_atomic_read include/linux/instrumented.h:68 [inline]
BUG: KASAN: slab-use-after-free in atomic_read include/linux/atomic/atomic-instrumented.h:32 [inline]
BUG: KASAN: slab-use-after-free in refcount_read include/linux/refcount.h:136 [inline]
BUG: KASAN: slab-use-after-free in skb_unref include/linux/skbuff.h:1228 [inline]
BUG: KASAN: slab-use-after-free in __sk_skb_reason_drop net/core/skbuff.c:1196 [inline]
BUG: KASAN: slab-use-after-free in sk_skb_reason_drop+0x44/0x3d0 net/core/skbuff.c:1224
Read of size 4 at addr ffff8880659b7c24 by task syz-executor.0/5174

CPU: 0 PID: 5174 Comm: syz-executor.0 Not tainted 6.10.0-rc4-syzkaller-00874-g84562f9953ec #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
print_address_description mm/kasan/report.c:377 [inline]
print_report+0x169/0x550 mm/kasan/report.c:488
kasan_report+0x143/0x180 mm/kasan/report.c:601
kasan_check_range+0x282/0x290 mm/kasan/generic.c:189
instrument_atomic_read include/linux/instrumented.h:68 [inline]
atomic_read include/linux/atomic/atomic-instrumented.h:32 [inline]
refcount_read include/linux/refcount.h:136 [inline]
skb_unref include/linux/skbuff.h:1228 [inline]
__sk_skb_reason_drop net/core/skbuff.c:1196 [inline]
sk_skb_reason_drop+0x44/0x3d0 net/core/skbuff.c:1224
kfree_skb_reason include/linux/skbuff.h:1260 [inline]
kfree_skb include/linux/skbuff.h:1269 [inline]
__hci_req_sync+0x631/0x950 net/bluetooth/hci_request.c:184
hci_req_sync+0xa9/0xd0 net/bluetooth/hci_request.c:206
hci_dev_cmd+0x4c5/0xa50 net/bluetooth/hci_core.c:787
sock_do_ioctl+0x158/0x460 net/socket.c:1222
sock_ioctl+0x629/0x8e0 net/socket.c:1341
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:907 [inline]
__se_sys_ioctl+0xfc/0x170 fs/ioctl.c:893
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f933f27ce0b
Code: 00 48 89 44 24 18 31 c0 48 8d 44 24 60 c7 04 24 10 00 00 00 48 89 44 24 08 48 8d 44 24 20 48 89 44 24 10 b8 10 00 00 00 0f 05 <89> c2 3d 00 f0 ff ff 77 1c 48 8b 44 24 18 64 48 2b 04 25 28 00 00
RSP: 002b:00007ffe546c6fc0 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f933f27ce0b
RDX: 00007ffe546c7038 RSI: 00000000400448dd RDI: 0000000000000003
RBP: 000055558c4c3430 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000008 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000001 R15: 0000000000000001
</TASK>

Allocated by task 4493:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
unpoison_slab_object mm/kasan/common.c:312 [inline]
__kasan_slab_alloc+0x66/0x80 mm/kasan/common.c:338
kasan_slab_alloc include/linux/kasan.h:201 [inline]
slab_post_alloc_hook mm/slub.c:3941 [inline]
slab_alloc_node mm/slub.c:4001 [inline]
kmem_cache_alloc_noprof+0x135/0x2a0 mm/slub.c:4008
skb_clone+0x20c/0x390 net/core/skbuff.c:2054
hci_send_cmd_sync net/bluetooth/hci_core.c:4123 [inline]
hci_cmd_work+0x2a2/0x670 net/bluetooth/hci_core.c:4143
process_one_work kernel/workqueue.c:3231 [inline]
process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3312
worker_thread+0x86d/0xd70 kernel/workqueue.c:3393
kthread+0x2f0/0x390 kernel/kthread.c:389
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Freed by task 4493:
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:579
poison_slab_object+0xe0/0x150 mm/kasan/common.c:240
__kasan_slab_free+0x37/0x60 mm/kasan/common.c:256
kasan_slab_free include/linux/kasan.h:184 [inline]
slab_free_hook mm/slub.c:2196 [inline]
slab_free mm/slub.c:4437 [inline]
kmem_cache_free+0x145/0x350 mm/slub.c:4512
kfree_skb_reason include/linux/skbuff.h:1260 [inline]
kfree_skb include/linux/skbuff.h:1269 [inline]
hci_req_sync_complete+0xe8/0x290 net/bluetooth/hci_request.c:109
hci_event_packet+0xc75/0x1540 net/bluetooth/hci_event.c:7479
hci_rx_work+0x3e8/0xca0 net/bluetooth/hci_core.c:4074
process_one_work kernel/workqueue.c:3231 [inline]
process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3312
worker_thread+0x86d/0xd70 kernel/workqueue.c:3393
kthread+0x2f0/0x390 kernel/kthread.c:389
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

The buggy address belongs to the object at ffff8880659b7b40
which belongs to the cache skbuff_head_cache of size 240
The buggy address is located 228 bytes inside of
freed 240-byte region [ffff8880659b7b40, ffff8880659b7c30)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x659b7
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffefff(slab)
raw: 00fff00000000000 ffff888018e98780 dead000000000122 0000000000000000
raw: 0000000000000000 00000000000c000c 00000001ffffefff 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 0x152cc0(GFP_USER|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 5175, tgid 5175 (kworker/u9:2), ts 61702947833, free_ts 61656603903
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1468
prep_new_page mm/page_alloc.c:1476 [inline]
get_page_from_freelist+0x2e43/0x2f00 mm/page_alloc.c:3420
__alloc_pages_noprof+0x256/0x6c0 mm/page_alloc.c:4678
__alloc_pages_node_noprof include/linux/gfp.h:269 [inline]
alloc_pages_node_noprof include/linux/gfp.h:296 [inline]
alloc_slab_page+0x5f/0x120 mm/slub.c:2265
allocate_slab+0x5a/0x2f0 mm/slub.c:2428
new_slab mm/slub.c:2481 [inline]
___slab_alloc+0xcd1/0x14b0 mm/slub.c:3667
__slab_alloc+0x58/0xa0 mm/slub.c:3757
__slab_alloc_node mm/slub.c:3810 [inline]
slab_alloc_node mm/slub.c:3989 [inline]
kmem_cache_alloc_noprof+0x1c1/0x2a0 mm/slub.c:4008
skb_clone+0x20c/0x390 net/core/skbuff.c:2054
hci_send_cmd_sync net/bluetooth/hci_core.c:4123 [inline]
hci_cmd_work+0x2a2/0x670 net/bluetooth/hci_core.c:4143
process_one_work kernel/workqueue.c:3231 [inline]
process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3312
worker_thread+0x86d/0xd70 kernel/workqueue.c:3393
kthread+0x2f0/0x390 kernel/kthread.c:389
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
page last free pid 5167 tgid 5167 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1088 [inline]
free_unref_page+0xd22/0xea0 mm/page_alloc.c:2583
vfree+0x186/0x2e0 mm/vmalloc.c:3346
kcov_put kernel/kcov.c:429 [inline]
kcov_close+0x2b/0x50 kernel/kcov.c:525
__fput+0x406/0x8b0 fs/file_table.c:422
task_work_run+0x24f/0x310 kernel/task_work.c:180
exit_task_work include/linux/task_work.h:38 [inline]
do_exit+0xa27/0x27e0 kernel/exit.c:874
do_group_exit+0x207/0x2c0 kernel/exit.c:1023
get_signal+0x16a1/0x1740 kernel/signal.c:2909
arch_do_signal_or_restart+0x96/0x860 arch/x86/kernel/signal.c:310
exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
syscall_exit_to_user_mode+0xc9/0x370 kernel/entry/common.c:218
do_syscall_64+0x100/0x230 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
ffff8880659b7b00: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
ffff8880659b7b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8880659b7c00: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
^
ffff8880659b7c80: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880659b7d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc
==================================================================


---
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.

If the report is already addressed, 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 report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

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

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

[Edward Adam Davis]

please test uaf in sk_skb_reason_drop

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git 84562f9953ec

diff --git a/net/bluetooth/hci_request.c b/net/bluetooth/hci_request.c
index efea25eb56ce..6f3e2e6cd2f4 100644
--- a/net/bluetooth/hci_request.c
+++ b/net/bluetooth/hci_request.c
@@ -106,8 +106,10 @@ void hci_req_sync_complete(struct hci_dev *hdev, u8 result, u16 opcode,
hdev->req_result = result;
hdev->req_status = HCI_REQ_DONE;
if (skb) {
- kfree_skb(hdev->req_skb);
+ struct sk_buff *old_skb;
+ old_skb = hdev->req_skb;
hdev->req_skb = skb_get(skb);
+ kfree_skb(old_skb);
}
wake_up_interruptible(&hdev->req_wait_q);
}
@@ -120,6 +122,7 @@ int __hci_req_sync(struct hci_dev *hdev, int (*func)(struct hci_request *req,
{
struct hci_request req;
int err = 0;
+ struct sk_buff *req_skb;

bt_dev_dbg(hdev, "start");

@@ -181,8 +184,9 @@ int __hci_req_sync(struct hci_dev *hdev, int (*func)(struct hci_request *req,
break;
}

- kfree_skb(hdev->req_skb);
+ req_skb = hdev->req_skb;
hdev->req_skb = NULL;
+ kfree_skb(req_skb);
hdev->req_status = hdev->req_result = 0;

bt_dev_dbg(hdev, "end: err %d", err);

[syzbot]

Hello,

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

Reported-and-tested-by: syzbot+f115fc...@syzkaller.appspotmail.com

Tested on:

commit: 84562f99 Merge branch '100GbE' of git://git.kernel.org..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
console output: https://syzkaller.appspot.com/x/log.txt?x=17f0202a980000

kernel config: https://syzkaller.appspot.com/x/.config?x=e78fc116033e0ab7
dashboard link: https://syzkaller.appspot.com/bug?extid=f115fcf7e49b2ebc902d
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=12de383e980000

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

[Hillf Danton]

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 2ccbdf43d5e7

--- x/net/bluetooth/hci_request.c
+++ h/net/bluetooth/hci_request.c
@@ -160,6 +160,8 @@ int __hci_req_sync(struct hci_dev *hdev,

if (err == -ERESTARTSYS)
return -EINTR;
+ if (!err)
+ return -ETIMEDOUT;

switch (hdev->req_status) {
case HCI_REQ_DONE:
--

[syzbot]

Hello,

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

Reported-and-tested-by: syzbot+f115fc...@syzkaller.appspotmail.com

Tested on:

commit: 2ccbdf43 Merge tag 'for-linus' of git://git.kernel.org..
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=175a07b6980000
kernel config: https://syzkaller.appspot.com/x/.config?x=1437ab35b9d90e65

dashboard link: https://syzkaller.appspot.com/bug?extid=f115fcf7e49b2ebc902d
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=12f1f389980000