@@ -17,6 +17,7 @@
static u8 llcp_magic[3] = {0x46, 0x66, 0x6d};
static LIST_HEAD(llcp_devices);
+static DEFINE_SPINLOCK(llcp_devices_list_lock);
static void nfc_llcp_rx_skb(struct nfc_llcp_local *local, struct sk_buff *skb);
@@ -168,7 +169,9 @@ static void local_release(struct kref *ref)
local = container_of(ref, struct nfc_llcp_local, ref);
+ spin_lock(&llcp_devices_list_lock);
list_del(&local->list);
+ spin_unlock(&llcp_devices_list_lock);
local_cleanup(local);
kfree(local);
}
@@ -282,9 +285,13 @@ struct nfc_llcp_local *nfc_llcp_find_local(struct nfc_dev *dev)
{
struct nfc_llcp_local *local;
+ spin_lock(&llcp_devices_list_lock);
list_for_each_entry(local, &llcp_devices, list)
- if (local->dev == dev)
+ if (local->dev == dev) {
+ spin_unlock(&llcp_devices_list_lock);
return local;
+ }
+ spin_unlock(&llcp_devices_list_lock);
pr_debug("No device found\n");
@@ -1600,7 +1607,9 @@ int nfc_llcp_register_device(struct nfc_dev *ndev)
timer_setup(&local->sdreq_timer, nfc_llcp_sdreq_timer, 0);
INIT_WORK(&local->sdreq_timeout_work, nfc_llcp_sdreq_timeout_work);
+ spin_lock(&llcp_devices_list_lock);
list_add(&local->list, &llcp_devices);
+ spin_unlock(&llcp_devices_list_lock);
return 0;
}
There are multiple path operate llcp_devices list without protection: CPU0 CPU1 nfc_unregister_device() nfc_register_device() nfc_llcp_unregister_device() nfc_llcp_register_device() //no lock ... list_add(local->list, llcp_devices) local_release() list_del(local->list) CPU2 ... nfc_llcp_find_local() list_for_each_entry(,&llcp_devices,) So reach race condition if two of the three occur simultaneously, like following crash report, although there is no reproduction script in syzbot currently, our artificially constructed use cases can also reproduce it. list_del corruption. prev->next should be ffff888060ce7000, but was ffff88802a0ad000. (prev=ffffffff8e536240) ------------[ cut here ]------------ kernel BUG at lib/list_debug.c:59! invalid opcode: 0000 [#1] PREEMPT SMP KASAN CPU: 0 PID: 16622 Comm: syz-executor.5 Not tainted 6.1.0-rc6-next-20221125-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022 RIP: 0010:__list_del_entry_valid.cold+0x12/0x72 lib/list_debug.c:59 Code: f0 ff 0f 0b 48 89 f1 48 c7 c7 60 96 a6 8a 4c 89 e6 e8 4b 29 f0 ff 0f 0b 4c 89 e1 48 89 ee 48 c7 c7 c0 98 a6 8a e8 37 29 f0 ff <0f> 0b 48 89 ee 48 c7 c7 a0 97 a6 8a e8 26 29 f0 ff 0f 0b 4c 89 e2 RSP: 0018:ffffc900151afd58 EFLAGS: 00010282 RAX: 000000000000006d RBX: 0000000000000001 RCX: 0000000000000000 RDX: ffff88801e7eba80 RSI: ffffffff8166001c RDI: fffff52002a35f9d RBP: ffff888060ce7000 R08: 000000000000006d R09: 0000000000000000 R10: 0000000080000000 R11: 0000000000000000 R12: ffffffff8e536240 R13: ffff88801f3f3000 R14: ffff888060ce1000 R15: ffff888079d855f0 FS: 0000555556f57400(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f095d5ad988 CR3: 000000002155a000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> __list_del_entry include/linux/list.h:134 [inline] list_del include/linux/list.h:148 [inline] local_release net/nfc/llcp_core.c:171 [inline] kref_put include/linux/kref.h:65 [inline] nfc_llcp_local_put net/nfc/llcp_core.c:181 [inline] nfc_llcp_local_put net/nfc/llcp_core.c:176 [inline] nfc_llcp_unregister_device+0xb8/0x260 net/nfc/llcp_core.c:1619 nfc_unregister_device+0x196/0x330 net/nfc/core.c:1179 virtual_ncidev_close+0x52/0xb0 drivers/nfc/virtual_ncidev.c:163 __fput+0x27c/0xa90 fs/file_table.c:320 task_work_run+0x16f/0x270 kernel/task_work.c:179 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline] exit_to_user_mode_loop kernel/entry/common.c:171 [inline] exit_to_user_mode_prepare+0x23c/0x250 kernel/entry/common.c:203 __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline] syscall_exit_to_user_mode+0x1d/0x50 kernel/entry/common.c:296 do_syscall_64+0x46/0xb0 arch/x86/entry/common.c:86 entry_SYSCALL_64_after_hwframe+0x63/0xcd This patch add llcp_devices_list_lock lock to make it safe to process llcp_devices list. Fixes: 30cc4587659e ("NFC: Move LLCP code to the NFC top level diirectory") Reported-by: syzbot+81232c4a81a886e2b580@syzkaller.appspotmail.com Signed-off-by: Wang ShaoBo <bobo.shaobowang@huawei.com> --- v2: - replace mutex lock with spin lock net/nfc/llcp_core.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-)