[PATCH 6.19 100/311] Bluetooth: hci_sync: Fix UAF in le_read_features_complete

Greg Kroah-Hartman
2026-04-08T18:54:08Z

From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

[ Upstream commit 035c25007c9e698bef3826070ee34bb6d778020c ]

This fixes the following backtrace caused by hci_conn being freed
before le_read_features_complete but after
hci_le_read_remote_features_sync so hci_conn_del -> hci_cmd_sync_dequeue
is not able to prevent it:

==================================================================
BUG: KASAN: slab-use-after-free in instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
BUG: KASAN: slab-use-after-free in atomic_dec_and_test include/linux/atomic/atomic-instrumented.h:1383 [inline]
BUG: KASAN: slab-use-after-free in hci_conn_drop include/net/bluetooth/hci_core.h:1688 [inline]
BUG: KASAN: slab-use-after-free in le_read_features_complete+0x5b/0x340 net/bluetooth/hci_sync.c:7344
Write of size 4 at addr ffff8880796b0010 by task kworker/u9:0/52

CPU: 0 UID: 0 PID: 52 Comm: kworker/u9:0 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: hci0 hci_cmd_sync_work
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0xcd/0x630 mm/kasan/report.c:482
kasan_report+0xe0/0x110 mm/kasan/report.c:595
check_region_inline mm/kasan/generic.c:194 [inline]
kasan_check_range+0x100/0x1b0 mm/kasan/generic.c:200
instrument_atomic_read_write include/linux/instrumented.h:96 [inline]
atomic_dec_and_test include/linux/atomic/atomic-instrumented.h:1383 [inline]
hci_conn_drop include/net/bluetooth/hci_core.h:1688 [inline]
le_read_features_complete+0x5b/0x340 net/bluetooth/hci_sync.c:7344
hci_cmd_sync_work+0x1ff/0x430 net/bluetooth/hci_sync.c:334
process_one_work+0x9ba/0x1b20 kernel/workqueue.c:3257
process_scheduled_works kernel/workqueue.c:3340 [inline]
worker_thread+0x6c8/0xf10 kernel/workqueue.c:3421
kthread+0x3c5/0x780 kernel/kthread.c:463
ret_from_fork+0x983/0xb10 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
</TASK>

Allocated by task 5932:
kasan_save_stack+0x33/0x60 mm/kasan/common.c:56
kasan_save_track+0x14/0x30 mm/kasan/common.c:77
poison_kmalloc_redzone mm/kasan/common.c:400 [inline]
__kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:417
kmalloc_noprof include/linux/slab.h:957 [inline]
kzalloc_noprof include/linux/slab.h:1094 [inline]
__hci_conn_add+0xf8/0x1c70 net/bluetooth/hci_conn.c:963
hci_conn_add_unset+0x76/0x100 net/bluetooth/hci_conn.c:1084
le_conn_complete_evt+0x639/0x1f20 net/bluetooth/hci_event.c:5714
hci_le_enh_conn_complete_evt+0x23d/0x380 net/bluetooth/hci_event.c:5861
hci_le_meta_evt+0x357/0x5e0 net/bluetooth/hci_event.c:7408
hci_event_func net/bluetooth/hci_event.c:7716 [inline]
hci_event_packet+0x685/0x11c0 net/bluetooth/hci_event.c:7773
hci_rx_work+0x2c9/0xeb0 net/bluetooth/hci_core.c:4076
process_one_work+0x9ba/0x1b20 kernel/workqueue.c:3257
process_scheduled_works kernel/workqueue.c:3340 [inline]
worker_thread+0x6c8/0xf10 kernel/workqueue.c:3421
kthread+0x3c5/0x780 kernel/kthread.c:463
ret_from_fork+0x983/0xb10 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

Freed by task 5932:
kasan_save_stack+0x33/0x60 mm/kasan/common.c:56
kasan_save_track+0x14/0x30 mm/kasan/common.c:77
__kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:587
kasan_save_free_info mm/kasan/kasan.h:406 [inline]
poison_slab_object mm/kasan/common.c:252 [inline]
__kasan_slab_free+0x5f/0x80 mm/kasan/common.c:284
kasan_slab_free include/linux/kasan.h:234 [inline]
slab_free_hook mm/slub.c:2540 [inline]
slab_free mm/slub.c:6663 [inline]
kfree+0x2f8/0x6e0 mm/slub.c:6871
device_release+0xa4/0x240 drivers/base/core.c:2565
kobject_cleanup lib/kobject.c:689 [inline]
kobject_release lib/kobject.c:720 [inline]
kref_put include/linux/kref.h:65 [inline]
kobject_put+0x1e7/0x590 lib/kobject.c:737
put_device drivers/base/core.c:3797 [inline]
device_unregister+0x2f/0xc0 drivers/base/core.c:3920
hci_conn_del_sysfs+0xb4/0x180 net/bluetooth/hci_sysfs.c:79
hci_conn_cleanup net/bluetooth/hci_conn.c:173 [inline]
hci_conn_del+0x657/0x1180 net/bluetooth/hci_conn.c:1234
hci_disconn_complete_evt+0x410/0xa00 net/bluetooth/hci_event.c:3451
hci_event_func net/bluetooth/hci_event.c:7719 [inline]
hci_event_packet+0xa10/0x11c0 net/bluetooth/hci_event.c:7773
hci_rx_work+0x2c9/0xeb0 net/bluetooth/hci_core.c:4076
process_one_work+0x9ba/0x1b20 kernel/workqueue.c:3257
process_scheduled_works kernel/workqueue.c:3340 [inline]
worker_thread+0x6c8/0xf10 kernel/workqueue.c:3421
kthread+0x3c5/0x780 kernel/kthread.c:463
ret_from_fork+0x983/0xb10 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

The buggy address belongs to the object at ffff8880796b0000
which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 16 bytes inside of
freed 8192-byte region [ffff8880796b0000, ffff8880796b2000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x796b0
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
anon flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88813ff27280 0000000000000000 0000000000000001
raw: 0000000000000000 0000000000020002 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88813ff27280 0000000000000000 0000000000000001
head: 0000000000000000 0000000000020002 00000000f5000000 0000000000000000
head: 00fff00000000003 ffffea0001e5ac01 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 Unmovable, gfp_mask 0xd2040(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5657, tgid 5657 (dhcpcd-run-hook), ts 79819636908, free_ts 79814310558
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0x1af/0x220 mm/page_alloc.c:1845
prep_new_page mm/page_alloc.c:1853 [inline]
get_page_from_freelist+0xd0b/0x31a0 mm/page_alloc.c:3879
__alloc_frozen_pages_noprof+0x25f/0x2440 mm/page_alloc.c:5183
alloc_pages_mpol+0x1fb/0x550 mm/mempolicy.c:2416
alloc_slab_page mm/slub.c:3075 [inline]
allocate_slab mm/slub.c:3248 [inline]
new_slab+0x2c3/0x430 mm/slub.c:3302
___slab_alloc+0xe18/0x1c90 mm/slub.c:4651
__slab_alloc.constprop.0+0x63/0x110 mm/slub.c:4774
__slab_alloc_node mm/slub.c:4850 [inline]
slab_alloc_node mm/slub.c:5246 [inline]
__kmalloc_cache_noprof+0x477/0x800 mm/slub.c:5766
kmalloc_noprof include/linux/slab.h:957 [inline]
kzalloc_noprof include/linux/slab.h:1094 [inline]
tomoyo_print_bprm security/tomoyo/audit.c:26 [inline]
tomoyo_init_log+0xc8a/0x2140 security/tomoyo/audit.c:264
tomoyo_supervisor+0x302/0x13b0 security/tomoyo/common.c:2198
tomoyo_audit_env_log security/tomoyo/environ.c:36 [inline]
tomoyo_env_perm+0x191/0x200 security/tomoyo/environ.c:63
tomoyo_environ security/tomoyo/domain.c:672 [inline]
tomoyo_find_next_domain+0xec1/0x20b0 security/tomoyo/domain.c:888
tomoyo_bprm_check_security security/tomoyo/tomoyo.c:102 [inline]
tomoyo_bprm_check_security+0x12d/0x1d0 security/tomoyo/tomoyo.c:92
security_bprm_check+0x1b9/0x1e0 security/security.c:794
search_binary_handler fs/exec.c:1659 [inline]
exec_binprm fs/exec.c:1701 [inline]
bprm_execve fs/exec.c:1753 [inline]
bprm_execve+0x81e/0x1620 fs/exec.c:1729
do_execveat_common.isra.0+0x4a5/0x610 fs/exec.c:1859
page last free pid 5657 tgid 5657 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
free_pages_prepare mm/page_alloc.c:1394 [inline]
__free_frozen_pages+0x7df/0x1160 mm/page_alloc.c:2901
discard_slab mm/slub.c:3346 [inline]
__put_partials+0x130/0x170 mm/slub.c:3886
qlink_free mm/kasan/quarantine.c:163 [inline]
qlist_free_all+0x4c/0xf0 mm/kasan/quarantine.c:179
kasan_quarantine_reduce+0x195/0x1e0 mm/kasan/quarantine.c:286
__kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:352
kasan_slab_alloc include/linux/kasan.h:252 [inline]
slab_post_alloc_hook mm/slub.c:4948 [inline]
slab_alloc_node mm/slub.c:5258 [inline]
__kmalloc_cache_noprof+0x274/0x800 mm/slub.c:5766
kmalloc_noprof include/linux/slab.h:957 [inline]
tomoyo_print_header security/tomoyo/audit.c:156 [inline]
tomoyo_init_log+0x197/0x2140 security/tomoyo/audit.c:255
tomoyo_supervisor+0x302/0x13b0 security/tomoyo/common.c:2198
tomoyo_audit_env_log security/tomoyo/environ.c:36 [inline]
tomoyo_env_perm+0x191/0x200 security/tomoyo/environ.c:63
tomoyo_environ security/tomoyo/domain.c:672 [inline]
tomoyo_find_next_domain+0xec1/0x20b0 security/tomoyo/domain.c:888
tomoyo_bprm_check_security security/tomoyo/tomoyo.c:102 [inline]
tomoyo_bprm_check_security+0x12d/0x1d0 security/tomoyo/tomoyo.c:92
security_bprm_check+0x1b9/0x1e0 security/security.c:794
search_binary_handler fs/exec.c:1659 [inline]
exec_binprm fs/exec.c:1701 [inline]
bprm_execve fs/exec.c:1753 [inline]
bprm_execve+0x81e/0x1620 fs/exec.c:1729
do_execveat_common.isra.0+0x4a5/0x610 fs/exec.c:1859
do_execve fs/exec.c:1933 [inline]
__do_sys_execve fs/exec.c:2009 [inline]
__se_sys_execve fs/exec.c:2004 [inline]
__x64_sys_execve+0x8e/0xb0 fs/exec.c:2004
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94

Memory state around the buggy address:
ffff8880796aff00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8880796aff80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880796b0000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880796b0080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880796b0100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Fixes: a106e50be74b ("Bluetooth: HCI: Add support for LL Extended Feature Set")
Reported-by: syzbot+87badbb9094e008e0685@syzkaller.appspotmail.com
Tested-by: syzbot+87badbb9094e008e0685@syzkaller.appspotmail.com
Closes: https://syzbot.org/bug?extid=87badbb9094e008e0685
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Signed-off-by: Pauli Virtanen <pav@iki.fi>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/bluetooth/hci_sync.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
index 7dfd630d38f05..312526a5a1efb 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c
@@ -7359,10 +7359,8 @@ static void le_read_features_complete(struct hci_dev *hdev, void *data, int err)

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

- if (err == -ECANCELED)
- return;
-
hci_conn_drop(conn);
+ hci_conn_put(conn);
}

static int hci_le_read_all_remote_features_sync(struct hci_dev *hdev,
@@ -7432,10 +7430,12 @@ int hci_le_read_remote_features(struct hci_conn *conn)
if (conn->out || (hdev->le_features[0] & HCI_LE_PERIPHERAL_FEATURES)) {
err = hci_cmd_sync_queue_once(hdev,
hci_le_read_remote_features_sync,
- hci_conn_hold(conn),
+ hci_conn_hold(hci_conn_get(conn)),
le_read_features_complete);
- if (err)
+ if (err) {
hci_conn_drop(conn);
+ hci_conn_put(conn);
+ }
} else {
err = -EOPNOTSUPP;
}
--
2.53.0