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@@ -0,0 +1,149 @@
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+From 88f170814fea74911ceab798a43cbd7c5599bed4 Mon Sep 17 00:00:00 2001
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+From: Marios Makassikis <[email protected]>
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+Date: Wed, 15 Oct 2025 09:25:46 +0200
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+Subject: [PATCH] ksmbd: fix recursive locking in RPC handle list access
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+
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+Since commit 305853cce3794 ("ksmbd: Fix race condition in RPC handle list
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+access"), ksmbd_session_rpc_method() attempts to lock sess->rpc_lock.
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+
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+This causes hung connections / tasks when a client attempts to open
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+a named pipe. Using Samba's rpcclient tool:
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+
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+ $ rpcclient //192.168.1.254 -U user%password
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+ $ rpcclient $> srvinfo
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+ <connection hung here>
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+
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+Kernel side:
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+ "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
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+ task:kworker/0:0 state:D stack:0 pid:5021 tgid:5021 ppid:2 flags:0x00200000
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+ Workqueue: ksmbd-io handle_ksmbd_work
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+ Call trace:
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+ __schedule from schedule+0x3c/0x58
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+ schedule from schedule_preempt_disabled+0xc/0x10
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+ schedule_preempt_disabled from rwsem_down_read_slowpath+0x1b0/0x1d8
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+ rwsem_down_read_slowpath from down_read+0x28/0x30
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+ down_read from ksmbd_session_rpc_method+0x18/0x3c
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+ ksmbd_session_rpc_method from ksmbd_rpc_open+0x34/0x68
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+ ksmbd_rpc_open from ksmbd_session_rpc_open+0x194/0x228
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+ ksmbd_session_rpc_open from create_smb2_pipe+0x8c/0x2c8
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+ create_smb2_pipe from smb2_open+0x10c/0x27ac
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+ smb2_open from handle_ksmbd_work+0x238/0x3dc
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+ handle_ksmbd_work from process_scheduled_works+0x160/0x25c
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+ process_scheduled_works from worker_thread+0x16c/0x1e8
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+ worker_thread from kthread+0xa8/0xb8
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+ kthread from ret_from_fork+0x14/0x38
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+ Exception stack(0x8529ffb0 to 0x8529fff8)
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+
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+The task deadlocks because the lock is already held:
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+ ksmbd_session_rpc_open
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+ down_write(&sess->rpc_lock)
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+ ksmbd_rpc_open
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+ ksmbd_session_rpc_method
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+ down_read(&sess->rpc_lock) <-- deadlock
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+
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+Adjust ksmbd_session_rpc_method() callers to take the lock when necessary.
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+
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+Fixes: 305853cce3794 ("ksmbd: Fix race condition in RPC handle list access")
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+Signed-off-by: Marios Makassikis <[email protected]>
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+Acked-by: Namjae Jeon <[email protected]>
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+Signed-off-by: Steve French <[email protected]>
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+---
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+ fs/smb/server/mgmt/user_session.c | 7 ++-----
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+ fs/smb/server/smb2pdu.c | 9 ++++++++-
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+ fs/smb/server/transport_ipc.c | 12 ++++++++++++
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+ 3 files changed, 22 insertions(+), 6 deletions(-)
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+
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+--- a/fs/smb/server/mgmt/user_session.c
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++++ b/fs/smb/server/mgmt/user_session.c
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+@@ -147,14 +147,11 @@ void ksmbd_session_rpc_close(struct ksmb
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+ int ksmbd_session_rpc_method(struct ksmbd_session *sess, int id)
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+ {
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+ struct ksmbd_session_rpc *entry;
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+- int method;
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+
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+- down_read(&sess->rpc_lock);
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++ lockdep_assert_held(&sess->rpc_lock);
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+ entry = xa_load(&sess->rpc_handle_list, id);
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+- method = entry ? entry->method : 0;
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+- up_read(&sess->rpc_lock);
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+
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+- return method;
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++ return entry ? entry->method : 0;
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+ }
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+
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+ void ksmbd_session_destroy(struct ksmbd_session *sess)
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+--- a/fs/smb/server/smb2pdu.c
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++++ b/fs/smb/server/smb2pdu.c
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+@@ -4623,8 +4623,15 @@ static int smb2_get_info_file_pipe(struc
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+ * pipe without opening it, checking error condition here
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+ */
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+ id = req->VolatileFileId;
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+- if (!ksmbd_session_rpc_method(sess, id))
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++
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++ lockdep_assert_not_held(&sess->rpc_lock);
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++
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++ down_read(&sess->rpc_lock);
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++ if (!ksmbd_session_rpc_method(sess, id)) {
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++ up_read(&sess->rpc_lock);
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+ return -ENOENT;
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++ }
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++ up_read(&sess->rpc_lock);
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+
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+ ksmbd_debug(SMB, "FileInfoClass %u, FileId 0x%llx\n",
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+ req->FileInfoClass, req->VolatileFileId);
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+--- a/fs/smb/server/transport_ipc.c
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++++ b/fs/smb/server/transport_ipc.c
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+@@ -825,6 +825,9 @@ struct ksmbd_rpc_command *ksmbd_rpc_writ
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+ if (!msg)
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+ return NULL;
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+
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++ lockdep_assert_not_held(&sess->rpc_lock);
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++
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++ down_read(&sess->rpc_lock);
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+ msg->type = KSMBD_EVENT_RPC_REQUEST;
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+ req = (struct ksmbd_rpc_command *)msg->payload;
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+ req->handle = handle;
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+@@ -833,6 +836,7 @@ struct ksmbd_rpc_command *ksmbd_rpc_writ
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+ req->flags |= KSMBD_RPC_WRITE_METHOD;
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+ req->payload_sz = payload_sz;
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+ memcpy(req->payload, payload, payload_sz);
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++ up_read(&sess->rpc_lock);
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+
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+ resp = ipc_msg_send_request(msg, req->handle);
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+ ipc_msg_free(msg);
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+@@ -849,6 +853,9 @@ struct ksmbd_rpc_command *ksmbd_rpc_read
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+ if (!msg)
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+ return NULL;
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+
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++ lockdep_assert_not_held(&sess->rpc_lock);
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++
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++ down_read(&sess->rpc_lock);
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+ msg->type = KSMBD_EVENT_RPC_REQUEST;
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+ req = (struct ksmbd_rpc_command *)msg->payload;
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+ req->handle = handle;
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+@@ -856,6 +863,7 @@ struct ksmbd_rpc_command *ksmbd_rpc_read
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+ req->flags |= rpc_context_flags(sess);
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+ req->flags |= KSMBD_RPC_READ_METHOD;
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+ req->payload_sz = 0;
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++ up_read(&sess->rpc_lock);
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+
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+ resp = ipc_msg_send_request(msg, req->handle);
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+ ipc_msg_free(msg);
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+@@ -876,6 +884,9 @@ struct ksmbd_rpc_command *ksmbd_rpc_ioct
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+ if (!msg)
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+ return NULL;
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+
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++ lockdep_assert_not_held(&sess->rpc_lock);
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++
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++ down_read(&sess->rpc_lock);
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+ msg->type = KSMBD_EVENT_RPC_REQUEST;
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+ req = (struct ksmbd_rpc_command *)msg->payload;
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+ req->handle = handle;
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+@@ -884,6 +895,7 @@ struct ksmbd_rpc_command *ksmbd_rpc_ioct
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+ req->flags |= KSMBD_RPC_IOCTL_METHOD;
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+ req->payload_sz = payload_sz;
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+ memcpy(req->payload, payload, payload_sz);
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++ up_read(&sess->rpc_lock);
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+
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+ resp = ipc_msg_send_request(msg, req->handle);
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+ ipc_msg_free(msg);
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Edoardo Pinci