The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From ef68e831840c40c7d01b328b3c0f5d8c4796c232 Mon Sep 17 00:00:00 2001
From: Pavel Shilovsky pshilov@microsoft.com Date: Fri, 18 Jan 2019 17:25:36 -0800 Subject: [PATCH] CIFS: Do not reconnect TCP session in add_credits()
When executing add_credits() we currently call cifs_reconnect() if the number of credits is zero and there are no requests in flight. In this case we may call cifs_reconnect() recursively twice and cause memory corruption given the following sequence of functions:
mid1.callback() -> add_credits() -> cifs_reconnect() -> -> mid2.callback() -> add_credits() -> cifs_reconnect().
Fix this by avoiding to call cifs_reconnect() in add_credits() and checking for zero credits in the demultiplex thread.
Cc: stable@vger.kernel.org Signed-off-by: Pavel Shilovsky pshilov@microsoft.com Reviewed-by: Ronnie Sahlberg lsahlber@redhat.com Signed-off-by: Steve French stfrench@microsoft.com
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c index 683310f26171..8463c940e0e5 100644 --- a/fs/cifs/connect.c +++ b/fs/cifs/connect.c @@ -720,6 +720,21 @@ server_unresponsive(struct TCP_Server_Info *server) return false; }
+static inline bool +zero_credits(struct TCP_Server_Info *server) +{ + int val; + + spin_lock(&server->req_lock); + val = server->credits + server->echo_credits + server->oplock_credits; + if (server->in_flight == 0 && val == 0) { + spin_unlock(&server->req_lock); + return true; + } + spin_unlock(&server->req_lock); + return false; +} + static int cifs_readv_from_socket(struct TCP_Server_Info *server, struct msghdr *smb_msg) { @@ -732,6 +747,12 @@ cifs_readv_from_socket(struct TCP_Server_Info *server, struct msghdr *smb_msg) for (total_read = 0; msg_data_left(smb_msg); total_read += length) { try_to_freeze();
+ /* reconnect if no credits and no requests in flight */ + if (zero_credits(server)) { + cifs_reconnect(server); + return -ECONNABORTED; + } + if (server_unresponsive(server)) return -ECONNABORTED; if (cifs_rdma_enabled(server) && server->smbd_conn) diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c index 1d3ce127b02e..fa8d2e1076c8 100644 --- a/fs/cifs/smb2ops.c +++ b/fs/cifs/smb2ops.c @@ -34,6 +34,7 @@ #include "cifs_ioctl.h" #include "smbdirect.h"
+/* Change credits for different ops and return the total number of credits */ static int change_conf(struct TCP_Server_Info *server) { @@ -41,17 +42,15 @@ change_conf(struct TCP_Server_Info *server) server->oplock_credits = server->echo_credits = 0; switch (server->credits) { case 0: - return -1; + return 0; case 1: server->echoes = false; server->oplocks = false; - cifs_dbg(VFS, "disabling echoes and oplocks\n"); break; case 2: server->echoes = true; server->oplocks = false; server->echo_credits = 1; - cifs_dbg(FYI, "disabling oplocks\n"); break; default: server->echoes = true; @@ -64,14 +63,15 @@ change_conf(struct TCP_Server_Info *server) server->echo_credits = 1; } server->credits -= server->echo_credits + server->oplock_credits; - return 0; + return server->credits + server->echo_credits + server->oplock_credits; }
static void smb2_add_credits(struct TCP_Server_Info *server, const unsigned int add, const int optype) { - int *val, rc = 0; + int *val, rc = -1; + spin_lock(&server->req_lock); val = server->ops->get_credits_field(server, optype);
@@ -101,8 +101,26 @@ smb2_add_credits(struct TCP_Server_Info *server, const unsigned int add, } spin_unlock(&server->req_lock); wake_up(&server->request_q); - if (rc) - cifs_reconnect(server); + + if (server->tcpStatus == CifsNeedReconnect) + return; + + switch (rc) { + case -1: + /* change_conf hasn't been executed */ + break; + case 0: + cifs_dbg(VFS, "Possible client or server bug - zero credits\n"); + break; + case 1: + cifs_dbg(VFS, "disabling echoes and oplocks\n"); + break; + case 2: + cifs_dbg(FYI, "disabling oplocks\n"); + break; + default: + cifs_dbg(FYI, "add %u credits total=%d\n", add, rc); + } }
static void