The approach taken to address the 'CVE-2024-35978' introduced another
double-free vulnerability. commit 45d355a926ab
("Bluetooth: Fix memory leak in hci_req_sync_complete()")
'hdev->req_skb' double free scenario:
cpu1 cpu2
==== ====
sock_ioctl
sock_do_ioctl
hci_sock_ioctl
hci_dev_cmd
hci_req_sync
__hci_req_sync hci_rx_work
kfree_skb(hdev->req_skb) hci_event_packet
(sleep) hci_req_sync_complete
\__ Longer times, kfree_skb(hdev->req_skb)
reproduce well hdev->req_skb = NULL
The longer cpu1 sleep in '__hci_req_sync', the more reproducible it is.
We've tested it by inserting the 'msleep()' function, and it's frequently
at 1000ms, and It has been consistently reproducible at 2000ms.
We confirmed the detection with various workloads that cause CPU1 to sleep.
The call trace below is one of the KASAN has seen.
Bluetooth: hci0: unexpected cc 0x0c38 length: 249 > 2
==================================================================
BUG: KASAN: slab-use-after-free in skb_release_data+0x7d8/0x8a0 home/paran/linux/net/core/skbuff.c:1119
Write of size 1 at addr ffff00000947d3fe by task syz-executor.2/2010
CPU: 1 PID: 2010 Comm: syz-executor.2 Not tainted
6.10.0-rc4-00217-g35bb670d65fc-dirty #22 Hardware name: linux,dummy-virt (DT)
Call trace:
dump_backtrace+0x318/0x348 home/paran/linux/arch/arm64/kernel/stacktrace.c:317
show_stack+0x4c/0x80 home/paran/linux/arch/arm64/kernel/stacktrace.c:324
__dump_stack home/paran/linux/lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x214/0x328 home/paran/linux/lib/dump_stack.c:114
print_address_description home/paran/linux/mm/kasan/report.c:377 [inline]
print_report+0x2ac/0x948 home/paran/linux/mm/kasan/report.c:488
kasan_report+0xc8/0x148 home/paran/linux/mm/kasan/report.c:601
__asan_report_store1_noabort+0x44/0x60 home/paran/linux/mm/kasan/report_generic.c:383
skb_release_data+0x7d8/0x8a0 home/paran/linux/net/core/skbuff.c:1119
skb_release_all+0x80/0xe0 home/paran/linux/net/core/skbuff.c:1173
__kfree_skb home/paran/linux/net/core/skbuff.c:1187 [inline]
kfree_skb_reason+0x138/0x3a8 home/paran/linux/net/core/skbuff.c:1223
__hci_req_sync+0x404/0x948 [bluetooth]
hci_req_sync+0xc0/0x138 [bluetooth]
hci_dev_cmd+0x33c/0xc18 [bluetooth]
hci_sock_ioctl+0x800/0xb68 [bluetooth]
sock_do_ioctl+0xfc/0x2e0 home/paran/linux/net/socket.c:1222
sock_ioctl+0x62c/0xab0 home/paran/linux/net/socket.c:1341
vfs_ioctl+0x90/0x140 home/paran/linux/fs/ioctl.c:51
__do_sys_ioctl home/paran/linux/fs/ioctl.c:907 [inline]
__se_sys_ioctl home/paran/linux/fs/ioctl.c:893 [inline]
__arm64_sys_ioctl+0x218/0x268 home/paran/linux/fs/ioctl.c:893
__invoke_syscall home/paran/linux/arch/arm64/kernel/syscall.c:34 [inline]
invoke_syscall+0xdc/0x460 home/paran/linux/arch/arm64/kernel/syscall.c:48
el0_svc_common.constprop.0+0x2d4/0x3e8 home/paran/linux/arch/arm64/kernel/syscall.c:133
do_el0_svc+0x60/0x98 home/paran/linux/arch/arm64/kernel/syscall.c:152
el0_svc+0xc4/0x240 home/paran/linux/arch/arm64/kernel/entry-common.c:712
el0t_64_sync_handler+0x120/0x130 home/paran/linux/arch/arm64/kernel/entry-common.c:730
el0t_64_sync+0x190/0x198 home/paran/linux/arch/arm64/kernel/entry.S:598
Allocated by task 577:
kasan_save_stack+0x48/0x90 home/paran/linux/mm/kasan/common.c:47
kasan_save_track+0x38/0x60 home/paran/linux/mm/kasan/common.c:68
kasan_save_alloc_info+0x64/0xc0 home/paran/linux/mm/kasan/generic.c:565
unpoison_slab_object home/paran/linux/mm/kasan/common.c:312 [inline]
__kasan_slab_alloc+0x100/0x110 home/paran/linux/mm/kasan/common.c:338
kasan_slab_alloc home/paran/linux/./include/linux/kasan.h:201 [inline]
slab_post_alloc_hook home/paran/linux/mm/slub.c:3941 [inline]
slab_alloc_node home/paran/linux/mm/slub.c:4001 [inline]
kmem_cache_alloc_noprof+0x2e8/0x630 home/paran/linux/mm/slub.c:4008
skb_clone+0x1a4/0x4d0 home/paran/linux/net/core/skbuff.c:2052
hci_cmd_work+0x78c/0x868 [bluetooth]
process_one_work home/paran/linux/kernel/workqueue.c:3231 [inline]
process_scheduled_works+0x9fc/0x1d98 home/paran/linux/kernel/workqueue.c:3312
worker_thread+0x57c/0xf98 home/paran/linux/kernel/workqueue.c:3393
kthread+0x3c8/0x478 home/paran/linux/kernel/kthread.c:389
ret_from_fork+0x10/0x20 home/paran/linux/arch/arm64/kernel/entry.S:860
Freed by task 577:
kasan_save_stack+0x48/0x90 home/paran/linux/mm/kasan/common.c:47
kasan_save_track+0x38/0x60 home/paran/linux/mm/kasan/common.c:68
kasan_save_free_info+0x64/0xf0 home/paran/linux/mm/kasan/generic.c:579
poison_slab_object+0x168/0x270 home/paran/linux/mm/kasan/common.c:240
__kasan_slab_free+0x34/0xa0 home/paran/linux/mm/kasan/common.c:256
kasan_slab_free home/paran/linux/./include/linux/kasan.h:184 [inline]
slab_free_hook home/paran/linux/mm/slub.c:2196 [inline]
slab_free home/paran/linux/mm/slub.c:4437 [inline]
kmem_cache_free+0x20c/0x670 home/paran/linux/mm/slub.c:4512
kfree_skbmem+0x2b0/0x390 home/paran/linux/net/core/skbuff.c:1131
__kfree_skb home/paran/linux/net/core/skbuff.c:1188 [inline]
kfree_skb_reason+0x14c/0x3a8 home/paran/linux/net/core/skbuff.c:1223
hci_req_sync_complete+0x114/0x308 [bluetooth]
hci_event_packet+0xa10/0x12a0 [bluetooth]
hci_rx_work+0x4d8/0xa80 [bluetooth]
process_one_work home/paran/linux/kernel/workqueue.c:3231 [inline]
process_scheduled_works+0x9fc/0x1d98 home/paran/linux/kernel/workqueue.c:3312
worker_thread+0x57c/0xf98 home/paran/linux/kernel/workqueue.c:3393
kthread+0x3c8/0x478 home/paran/linux/kernel/kthread.c:389
ret_from_fork+0x10/0x20 home/paran/linux/arch/arm64/kernel/entry.S:860
The buggy address belongs to the object at ffff00000947d380
which belongs to the cache skbuff_head_cache of size 232
The buggy address is located 126 bytes inside of
freed 232-byte region [ffff00000947d380, ffff00000947d468)
The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x4947c
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
memcg:ffff0000222a73b1
flags: 0x3fffe0000000040(head|node=0|zone=0|lastcpupid=0x1ffff)
page_type: 0xffffefff(slab)
raw: 03fffe0000000040 ffff0000133a41c0 fffffdffc0e3a090 fffffdffc1069290
raw: 0000000000000000 0000000000120012 00000001ffffefff ffff0000222a73b1
head: 03fffe0000000040 ffff0000133a41c0 fffffdffc0e3a090 fffffdffc1069290
head: 0000000000000000 0000000000120012 00000001ffffefff ffff0000222a73b1
head: 03fffe0000000001 fffffdffc0251f01 ffffffffffffffff 0000000000000000
head: 0000000000000002 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff00000947d280: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
ffff00000947d300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff00000947d380: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff00000947d400: fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc
ffff00000947d480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
We considered using the "hci_req_sync_lock" mutex, but concluded it
wasn't a good solution due to the increased sleep intervals causing
this issue. Instead, we introduced a spinlock member on 'struct hci_dev'.
Since applying our patch, we have repeatedly run the same tests in
the syzkaller without encountering any issues.
Link: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=89a32741f4217856066c198a4a7267bcdd1edd67
Fixes: 45d355a926ab ("Bluetooth: Fix memory leak in hci_req_sync_complete()")
Signed-off-by: Levi Yun <yeoreum.yun@xxxxxxx>
Signed-off-by: Yunseong Kim <yskelg@xxxxxxxxx>
---
include/net/bluetooth/hci_core.h | 1 +
net/bluetooth/hci_core.c | 1 +
net/bluetooth/hci_request.c | 6 ++----
net/bluetooth/hci_request.h | 9 +++++++++
net/bluetooth/hci_sync.c | 13 +++----------
5 files changed, 16 insertions(+), 14 deletions(-)
diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
index c43716edf205..8b95061f063b 100644
--- a/include/net/bluetooth/hci_core.h
+++ b/include/net/bluetooth/hci_core.h
@@ -519,6 +519,7 @@ struct hci_dev {
struct sk_buff *recv_event;
struct mutex req_lock;
+ spinlock_t req_skb_lock;
wait_queue_head_t req_wait_q;
__u32 req_status;
__u32 req_result;
diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index dd3b0f501018..138a6b19894d 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -2572,6 +2572,7 @@ struct hci_dev *hci_alloc_dev_priv(int sizeof_priv)
mutex_init(&hdev->lock);
mutex_init(&hdev->req_lock);
+ spin_lock_init(&hdev->req_skb_lock);
ida_init(&hdev->unset_handle_ida);
diff --git a/net/bluetooth/hci_request.c b/net/bluetooth/hci_request.c
index efea25eb56ce..6a109c1ad359 100644
--- a/net/bluetooth/hci_request.c
+++ b/net/bluetooth/hci_request.c
@@ -106,8 +106,7 @@ 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);
- hdev->req_skb = skb_get(skb);
+ hci_req_skb_release_and_set(hdev, skb_get(skb));
}
wake_up_interruptible(&hdev->req_wait_q);
}
@@ -181,8 +180,7 @@ int __hci_req_sync(struct hci_dev *hdev, int (*func)(struct hci_request *req,
break;
}
- kfree_skb(hdev->req_skb);
- hdev->req_skb = NULL;
+ hci_req_skb_release_and_set(hdev, NULL);
hdev->req_status = hdev->req_result = 0;
bt_dev_dbg(hdev, "end: err %d", err);
diff --git a/net/bluetooth/hci_request.h b/net/bluetooth/hci_request.h
index c91f2838f542..6526c78443bc 100644
--- a/net/bluetooth/hci_request.h
+++ b/net/bluetooth/hci_request.h
@@ -28,6 +28,15 @@
#define hci_req_sync_lock(hdev) mutex_lock(&hdev->req_lock)
#define hci_req_sync_unlock(hdev) mutex_unlock(&hdev->req_lock)
+#define hci_req_skb_release_and_set(hdev, val) \
+({ \
+ if (hdev->req_skb) { \
+ spin_lock(&hdev->req_skb_lock); \
+ kfree_skb(hdev->req_skb); \
+ hdev->req_skb = val; \
+ spin_unlock(&hdev->req_skb_lock); \
+ } \
+})
struct hci_request {
struct hci_dev *hdev;
diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
index a8a7d2b36870..25c8d858c82e 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c
@@ -33,8 +33,7 @@ static void hci_cmd_sync_complete(struct hci_dev *hdev, u8 result, u16 opcode,
hdev->req_status = HCI_REQ_DONE;
/* Free the request command so it is not used as response */
- kfree_skb(hdev->req_skb);
- hdev->req_skb = NULL;
+ hci_req_skb_release_and_set(hdev, NULL);
if (skb) {
struct sock *sk = hci_skb_sk(skb);
@@ -4935,10 +4934,7 @@ int hci_dev_open_sync(struct hci_dev *hdev)
hdev->sent_cmd = NULL;
}
- if (hdev->req_skb) {
- kfree_skb(hdev->req_skb);
- hdev->req_skb = NULL;
- }
+ hci_req_skb_release_and_set(hdev, NULL);
clear_bit(HCI_RUNNING, &hdev->flags);
hci_sock_dev_event(hdev, HCI_DEV_CLOSE);
@@ -5100,10 +5096,7 @@ int hci_dev_close_sync(struct hci_dev *hdev)
}
/* Drop last request */
- if (hdev->req_skb) {
- kfree_skb(hdev->req_skb);
- hdev->req_skb = NULL;
- }
+ hci_req_skb_release_and_set(hdev, NULL);
clear_bit(HCI_RUNNING, &hdev->flags);
hci_sock_dev_event(hdev, HCI_DEV_CLOSE);
--
2.45.2
