6.6-stable review patch. If anyone has any objections, please let me know.
------------------
From: Qianchang Zhao pioooooooooip@gmail.com
commit 1fab1fa091f5aa97265648b53ea031deedd26235 upstream.
ipc_msg_send_request() waits for a generic netlink reply using an ipc_msg_table_entry on the stack. The generic netlink handler (handle_generic_event()/handle_response()) fills entry->response under ipc_msg_table_lock, but ipc_msg_send_request() used to validate and free entry->response without holding the same lock.
Under high concurrency this allows a race where handle_response() is copying data into entry->response while ipc_msg_send_request() has just freed it, leading to a slab-use-after-free reported by KASAN in handle_generic_event():
BUG: KASAN: slab-use-after-free in handle_generic_event+0x3c4/0x5f0 [ksmbd] Write of size 12 at addr ffff888198ee6e20 by task pool/109349 ... Freed by task: kvfree ipc_msg_send_request [ksmbd] ksmbd_rpc_open -> ksmbd_session_rpc_open [ksmbd]
Fix by: - Taking ipc_msg_table_lock in ipc_msg_send_request() while validating entry->response, freeing it when invalid, and removing the entry from ipc_msg_table. - Returning the final entry->response pointer to the caller only after the hash entry is removed under the lock. - Returning NULL in the error path, preserving the original API semantics.
This makes all accesses to entry->response consistent with handle_response(), which already updates and fills the response buffer under ipc_msg_table_lock, and closes the race that allowed the UAF.
Cc: stable@vger.kernel.org Reported-by: Qianchang Zhao pioooooooooip@gmail.com Reported-by: Zhitong Liu liuzhitong1993@gmail.com Signed-off-by: Qianchang Zhao pioooooooooip@gmail.com Acked-by: Namjae Jeon linkinjeon@kernel.org Signed-off-by: Steve French stfrench@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/smb/server/transport_ipc.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
--- a/fs/smb/server/transport_ipc.c +++ b/fs/smb/server/transport_ipc.c @@ -520,12 +520,16 @@ static void *ipc_msg_send_request(struct up_write(&ipc_msg_table_lock);
ret = ipc_msg_send(msg); - if (ret) + if (ret) { + down_write(&ipc_msg_table_lock); goto out; + }
ret = wait_event_interruptible_timeout(entry.wait, entry.response != NULL, IPC_WAIT_TIMEOUT); + + down_write(&ipc_msg_table_lock); if (entry.response) { ret = ipc_validate_msg(&entry); if (ret) { @@ -534,7 +538,6 @@ static void *ipc_msg_send_request(struct } } out: - down_write(&ipc_msg_table_lock); hash_del(&entry.ipc_table_hlist); up_write(&ipc_msg_table_lock); return entry.response;