[PATCH v2] Bluetooth: hci_sync: Fix UAF in le_read_features_complete

[PATCH v2] Bluetooth: hci_sync: Fix UAF in le_read_features_complete

[Luiz Augusto von Dentz]

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

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>
---
 net/bluetooth/hci_sync.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
index 47d902310b19..91d0252ae661 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c
@@ -7393,7 +7393,7 @@ static void le_read_features_complete(struct hci_dev *hdev, void *data, int 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,
@@ -7463,10 +7463,10 @@ 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_get(conn),
 					      le_read_features_complete);
 		if (err)
-			hci_conn_drop(conn);
+			hci_conn_put(conn);
 	} else {
 		err = -EOPNOTSUPP;
 	}
-- 
2.53.0

RE: [v2] Bluetooth: hci_sync: Fix UAF in le_read_features_complete

[bluez.test.bot]

[-- Attachment #1: Type: text/plain, Size: 551 bytes --]

This is an automated email and please do not reply to this email.

Dear Submitter,

Thank you for submitting the patches to the linux bluetooth mailing list.
While preparing the CI tests, the patches you submitted couldn't be applied to the current HEAD of the repository.

----- Output -----

error: patch failed: net/bluetooth/hci_sync.c:7463
error: net/bluetooth/hci_sync.c: patch does not apply
hint: Use 'git am --show-current-patch' to see the failed patch

Please resolve the issue and submit the patches again.


---
Regards,
Linux Bluetooth

RE: [v2] Bluetooth: hci_sync: Fix UAF in le_read_features_complete

[bluez.test.bot]

[-- Attachment #1: Type: text/plain, Size: 2913 bytes --]

This is automated email and please do not reply to this email!

Dear submitter,

Thank you for submitting the patches to the linux bluetooth mailing list.
This is a CI test results with your patch series:
PW Link:https://patchwork.kernel.org/project/bluetooth/list/?series=1073172

---Test result---

Test Summary:
CheckPatch                    PENDING   0.32 seconds
GitLint                       PENDING   0.24 seconds
SubjectPrefix                 PASS      0.12 seconds
BuildKernel                   PASS      26.62 seconds
CheckAllWarning               PASS      28.87 seconds
CheckSparse                   PASS      27.82 seconds
BuildKernel32                 PASS      25.76 seconds
TestRunnerSetup               PASS      567.70 seconds
TestRunner_l2cap-tester       PASS      27.52 seconds
TestRunner_iso-tester         PASS      37.92 seconds
TestRunner_bnep-tester        PASS      6.50 seconds
TestRunner_mgmt-tester        FAIL      111.19 seconds
TestRunner_rfcomm-tester      PASS      9.37 seconds
TestRunner_sco-tester         FAIL      14.41 seconds
TestRunner_ioctl-tester       PASS      10.29 seconds
TestRunner_mesh-tester        FAIL      11.57 seconds
TestRunner_smp-tester         PASS      8.61 seconds
TestRunner_userchan-tester    PASS      6.73 seconds
IncrementalBuild              PENDING   0.60 seconds

Details
##############################
Test: CheckPatch - PENDING
Desc: Run checkpatch.pl script
Output:

##############################
Test: GitLint - PENDING
Desc: Run gitlint
Output:

##############################
Test: TestRunner_mgmt-tester - FAIL
Desc: Run mgmt-tester with test-runner
Output:
Total: 494, Passed: 485 (98.2%), Failed: 5, Not Run: 4

Failed Test Cases
Adv. connectable & connected (central) - Success     Failed       0.129 seconds
Adv. non-connectable & connected (central) - Success Failed       0.120 seconds
Ext Adv. connectable & connected (central)           Failed       0.175 seconds
Ext Adv. non-connectable & connected (central)       Failed       0.169 seconds
Read Exp Feature - Success                           Failed       0.108 seconds
##############################
Test: TestRunner_sco-tester - FAIL
Desc: Run sco-tester with test-runner
Output:
WARNING: possible circular locking dependency detected
BUG: sleeping function called from invalid context at net/core/sock.c:3782
Total: 30, Passed: 30 (100.0%), Failed: 0, Not Run: 0
##############################
Test: TestRunner_mesh-tester - FAIL
Desc: Run mesh-tester with test-runner
Output:
Total: 10, Passed: 8 (80.0%), Failed: 2, Not Run: 0

Failed Test Cases
Mesh - Send cancel - 1                               Timed out    1.887 seconds
Mesh - Send cancel - 2                               Timed out    1.992 seconds
##############################
Test: IncrementalBuild - PENDING
Desc: Incremental build with the patches in the series
Output:



---
Regards,
Linux Bluetooth

Re: [PATCH v2] Bluetooth: hci_sync: Fix UAF in le_read_features_complete

[patchwork-bot+bluetooth]

Hello:

This patch was applied to bluetooth/bluetooth-next.git (master)
by Luiz Augusto von Dentz <luiz.von.dentz@intel.com>:

On Thu, 26 Mar 2026 16:50:46 -0400 you wrote:
> From: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
> 
> 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:
> 
> [...]

Here is the summary with links:
  - [v2] Bluetooth: hci_sync: Fix UAF in le_read_features_complete
    https://git.kernel.org/bluetooth/bluetooth-next/c/60562bebb651

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html