[MM] - MF-196 Segmentation fault

["Gonzalez Calabozo, Jose Maria" <jmgonzalezc indra es>]

Hello,
I am testing the last ModemManager commit: f27dbda4a7b21aa4093d71c3886e67ca614e4f64 from the git repository 
and I have some issues.
The problem appears most of the times with the ZTE MF-196.

With ModemManager running I plug the modem, and then I force manual switching with:
usb_modeswitch -v 19d2 -p 1528 -c /etc/usb_modeswitch.d/19d2:0149
Unfortunately this modem does not switch to modem automatically in Fedora 18

After that, most of the times the following crash occurs:
ModemManager[32337]: <debug> [1363796739.044378] [mm-port-probe.c:137] mm_port_probe_set_result_at(): 
(tty/ttyACM0) port is AT-capable
ModemManager[32337]: <debug> [1363796739.044580] [mm-at-serial-port.c:397] debug_log(): (ttyACM2): <-- 
'ATE0+CPMS?'
ModemManager[32337]: <debug> [1363796739.044994] [mm-at-serial-port.c:397] debug_log(): (ttyACM2): <-- '<CR>'
ModemManager[32337]: <debug> [1363796739.046015] [mm-at-serial-port.c:397] debug_log(): (ttyACM2): <-- 
'<CR><LF>+CMS ERROR: SM BL not ready<CR><LF>'
Segmentation fault (core dumped)

I execute with gdb and I obtain the following call stack trace when the Segmentation fault happend:

#0  mm_message_error_for_string (str=0x703c80 "SM BL not ready") at mm-error-helpers.c:248
#1  0x000000000046520f in mm_serial_parser_v1_parse (data=0x7fffec0046a0, response=0x714ae0, 
error=0x7fffffffd408)
    at mm-serial-parsers.c:256
#2  0x0000000000484073 in parse_response (port=<optimized out>, response=0x7fffe8002580, 
error=0x7fffffffd408) at mm-at-serial-port.c:140
#3  0x000000000048323f in parse_response (error=0x7fffffffd408, response=<optimized out>, self=0x6e42f0) at 
mm-serial-port.c:734
#4  data_available (source=0x6e5f40, condition=<optimized out>, data=<optimized out>) at mm-serial-port.c:800
#5  0x0000003f83c47a75 in g_main_context_dispatch () from /lib64/libglib-2.0.so.0
#6  0x0000003f83c47da8 in g_main_context_iterate.isra.24 () from /lib64/libglib-2.0.so.0
#7  0x0000003f83c481a2 in g_main_loop_run () from /lib64/libglib-2.0.so.0
#8  0x0000000000424dd6 in main (argc=<optimized out>, argv=<optimized out>) at main.c:142

The problem lies in the following lines from mm-error-helpers.c
    /* Look for the string */
    for (i = 0; i < G_N_ELEMENTS (msg_errors); i++) {
        if (g_str_equal (msg_errors[i].error, buf)) {
            code = msg_errors[i].code;
            msg = msg_errors[i].message;
            break;
        }
    }

The msg_errors array has a length of 24 and for the last element the value of 'error' is NULL. So a call to 
g_str_equal (msg_errors[i].error, buf) will fail because it is expecting two valid pointers, but in this case 
msg_errors[i].error=0x0

So several patches can be applied to fix this issue.
The most simple is just to check the value of msg_errors[i].error:

--- a/src/mm-error-helpers.c
+++ b/src/mm-error-helpers.c
@@ -243,7 +243,7 @@ mm_message_error_for_string (const gchar *str)

     /* Look for the string */
     for (i = 0; i < G_N_ELEMENTS (msg_errors); i++) {
-        if (g_str_equal (msg_errors[i].error, buf)) {
+        if (msg_errors[i].error && g_str_equal (msg_errors[i].error, buf)) {
             code = msg_errors[i].code;
             msg = msg_errors[i].message;
             break;


Best regards,
José María González Calabozo

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