From 112b3fa92266ab36dbffa2abf66034203f66b2ce Mon Sep 17 00:00:00 2001
From: Yclept Nemo <pscjtwjdjtAhnbjm/dpn>
Date: Fri, 22 Jun 2018 23:02:07 -0400
Subject: stream_smb: locking to bypass libsmbclient issues

Thread-unsafe libsmbclient is likely to crash when used simultaneously
across threads. For example, by:

    mpv "smb://...mkv" --sub-file "smb://...srt"

Work around this by locking all calls to this library under a single
global mutex. This is a temporary solution. When the libsmbclient bug
[1] is fixed, switch to the code from branch [2] which uses a new api to
create per-thread smb contexts. Fixes [3].

[1] https://bugzilla.samba.org/show_bug.cgi?id=11413
[2] https://github.com/orbisvicis/mpv/tree/smbclient_threaded_api
[3] https://github.com/mpv-player/mpv/issues/5936
---
 stream/stream_smb.c | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/stream/stream_smb.c b/stream/stream_smb.c
index 4376f71ee6..822ffdbfb0 100644
--- a/stream/stream_smb.c
+++ b/stream/stream_smb.c
@@ -21,6 +21,7 @@
 
 #include <libsmbclient.h>
 #include <unistd.h>
+#include <pthread.h>
 
 #include "common/msg.h"
 #include "stream.h"
@@ -31,6 +32,8 @@
 #error GPL only
 #endif
 
+static pthread_mutex_t smb_lock = PTHREAD_MUTEX_INITIALIZER;
+
 struct priv {
     int fd;
 };
@@ -46,8 +49,10 @@ static int control(stream_t *s, int cmd, void *arg) {
   struct priv *p = s->priv;
   switch(cmd) {
     case STREAM_CTRL_GET_SIZE: {
+      pthread_mutex_lock(&smb_lock);
       off_t size = smbc_lseek(p->fd,0,SEEK_END);
       smbc_lseek(p->fd,s->pos,SEEK_SET);
+      pthread_mutex_unlock(&smb_lock);
       if(size != (off_t)-1) {
         *(int64_t *)arg = size;
         return 1;
@@ -60,7 +65,10 @@ static int control(stream_t *s, int cmd, void *arg) {
 
 static int seek(stream_t *s,int64_t newpos) {
   struct priv *p = s->priv;
-  if(smbc_lseek(p->fd,newpos,SEEK_SET)<0) {
+  pthread_mutex_lock(&smb_lock);
+  off_t size = smbc_lseek(p->fd,newpos,SEEK_SET);
+  pthread_mutex_unlock(&smb_lock);
+  if(size<0) {
     return 0;
   }
   return 1;
@@ -68,7 +76,9 @@ static int seek(stream_t *s,int64_t newpos) {
 
 static int fill_buffer(stream_t *s, char* buffer, int max_len){
   struct priv *p = s->priv;
+  pthread_mutex_lock(&smb_lock);
   int r = smbc_read(p->fd,buffer,max_len);
+  pthread_mutex_unlock(&smb_lock);
   return (r <= 0) ? -1 : r;
 }
 
@@ -77,7 +87,9 @@ static int write_buffer(stream_t *s, char* buffer, int len) {
   int r;
   int wr = 0;
   while (wr < len) {
+    pthread_mutex_lock(&smb_lock);
     r = smbc_write(p->fd,buffer,len);
+    pthread_mutex_unlock(&smb_lock);
     if (r <= 0)
       return -1;
     wr += r;
@@ -88,7 +100,9 @@ static int write_buffer(stream_t *s, char* buffer, int len) {
 
 static void close_f(stream_t *s){
   struct priv *p = s->priv;
+  pthread_mutex_lock(&smb_lock);
   smbc_close(p->fd);
+  pthread_mutex_unlock(&smb_lock);
 }
 
 static int open_f (stream_t *stream)
@@ -110,13 +124,17 @@ static int open_f (stream_t *stream)
     return STREAM_ERROR;
   }
 
+  pthread_mutex_lock(&smb_lock);
   err = smbc_init(smb_auth_fn, 1);
+  pthread_mutex_unlock(&smb_lock);
   if (err < 0) {
     MP_ERR(stream, "Cannot init the libsmbclient library: %d\n",err);
     return STREAM_ERROR;
   }
 
+  pthread_mutex_lock(&smb_lock);
   fd = smbc_open(filename, m,0644);
+  pthread_mutex_unlock(&smb_lock);
   if (fd < 0) {
     MP_ERR(stream, "Could not open from LAN: '%s'\n", filename);
     return STREAM_ERROR;
@@ -124,8 +142,10 @@ static int open_f (stream_t *stream)
 
   len = 0;
   if(!write) {
+    pthread_mutex_lock(&smb_lock);
     len = smbc_lseek(fd,0,SEEK_END);
     smbc_lseek (fd, 0, SEEK_SET);
+    pthread_mutex_unlock(&smb_lock);
   }
   if(len > 0 || write) {
     stream->seekable = true;
-- 
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