From 6988a619f5b79e4efadea6e19dcfe75fbcd350b5 Mon Sep 17 00:00:00 2001
From: Paulo Alcantara <pc@cjr.nz>
Date: Sat, 28 Nov 2020 15:57:06 -0300
Subject: [PATCH 1/2] cifs: allow syscalls to be restarted in __smb_send_rqst()
A customer has reported that several files in their multi-threaded app
were left with size of 0 because most of the read(2) calls returned
-EINTR and they assumed no bytes were read. Obviously, they could
have fixed it by simply retrying on -EINTR.
We noticed that most of the -EINTR on read(2) were due to real-time
signals sent by glibc to process wide credential changes (SIGRT_1),
and its signal handler had been established with SA_RESTART, in which
case those calls could have been automatically restarted by the
kernel.
Let the kernel decide to whether or not restart the syscalls when
there is a signal pending in __smb_send_rqst() by returning
-ERESTARTSYS. If it can't, it will return -EINTR anyway.
Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
CC: Stable <stable@vger.kernel.org>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
---
fs/cifs/transport.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
index e27e255d40dd8..36b2ece434037 100644
--- a/fs/cifs/transport.c
+++ b/fs/cifs/transport.c
@@ -339,8 +339,8 @@ __smb_send_rqst(struct TCP_Server_Info *server, int num_rqst,
return -EAGAIN;
if (signal_pending(current)) {
- cifs_dbg(FYI, "signal is pending before sending any data\n");
- return -EINTR;
+ cifs_dbg(FYI, "signal pending before send request\n");
+ return -ERESTARTSYS;
}
/* cork the socket */
From 212253367dc7b49ed3fc194ce71b0992eacaecf2 Mon Sep 17 00:00:00 2001
From: Paulo Alcantara <pc@cjr.nz>
Date: Sat, 28 Nov 2020 16:54:02 -0300
Subject: [PATCH 2/2] cifs: fix potential use-after-free in cifs_echo_request()
This patch fixes a potential use-after-free bug in
cifs_echo_request().
For instance,
thread 1
--------
cifs_demultiplex_thread()
clean_demultiplex_info()
kfree(server)
thread 2 (workqueue)
--------
apic_timer_interrupt()
smp_apic_timer_interrupt()
irq_exit()
__do_softirq()
run_timer_softirq()
call_timer_fn()
cifs_echo_request() <- use-after-free in server ptr
Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
CC: Stable <stable@vger.kernel.org>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
---
fs/cifs/connect.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index c38156f324ddb..28c1459fb0fc0 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -876,6 +876,8 @@ static void clean_demultiplex_info(struct TCP_Server_Info *server)
list_del_init(&server->tcp_ses_list);
spin_unlock(&cifs_tcp_ses_lock);
+ cancel_delayed_work_sync(&server->echo);
+
spin_lock(&GlobalMid_Lock);
server->tcpStatus = CifsExiting;
spin_unlock(&GlobalMid_Lock);