char: use a fixed idx for child muxed chr
mux_chr_update_read_handler() is adding a new mux_cnt each time mux_chr_update_read_handler() is called, it's not possible to actually update the "child" chr callbacks that were set previously. This may lead to crashes if the "child" chr is destroyed: valgrind x86_64-softmmu/qemu-system-x86_64 -chardev stdio,mux=on,id=char0 -mon chardev=char0,mode=control,default when quitting: ==4306== Invalid read of size 8 ==4306== at 0x8061D3: json_lexer_destroy (json-lexer.c:385) ==4306== by 0x7E39F8: json_message_parser_destroy (json-streamer.c:134) ==4306== by 0x3447F6: monitor_qmp_event (monitor.c:3908) ==4306== by 0x480153: mux_chr_send_event (qemu-char.c:630) ==4306== by 0x480694: mux_chr_event (qemu-char.c:734) ==4306== by 0x47F1E9: qemu_chr_be_event (qemu-char.c:205) ==4306== by 0x481207: fd_chr_close (qemu-char.c:1114) ==4306== by 0x481659: qemu_chr_close_stdio (qemu-char.c:1221) ==4306== by 0x486F07: qemu_chr_free (qemu-char.c:4146) ==4306== by 0x486F97: qemu_chr_delete (qemu-char.c:4154) ==4306== by 0x487E66: qemu_chr_cleanup (qemu-char.c:4678) ==4306== by 0x495A98: main (vl.c:4675) ==4306== Address 0x28439e90 is 112 bytes inside a block of size 240 free'd ==4306== at 0x4C2CD5A: free (vg_replace_malloc.c:530) ==4306== by 0x1E4CBF2D: g_free (in /usr/lib64/libglib-2.0.so.0.4800.2) ==4306== by 0x344DE9: monitor_cleanup (monitor.c:4058) ==4306== by 0x495A93: main (vl.c:4674) ==4306== Block was alloc'd at ==4306== at 0x4C2BBAD: malloc (vg_replace_malloc.c:299) ==4306== by 0x1E4CBE18: g_malloc (in /usr/lib64/libglib-2.0.so.0.4800.2) ==4306== by 0x344BF8: monitor_init (monitor.c:4021) ==4306== by 0x49063C: mon_init_func (vl.c:2417) ==4306== by 0x7FC6DE: qemu_opts_foreach (qemu-option.c:1116) ==4306== by 0x4954E0: main (vl.c:4473) Instead, keep the "child" chr associated with a particular idx so its handlers can be updated and removed to avoid the crash. Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com> Message-Id: <20161003094704.18087-3-marcandre.lureau@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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25a8535943
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949055a254
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@ -92,6 +92,7 @@ struct CharDriverState {
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int explicit_be_open;
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int avail_connections;
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int is_mux;
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int mux_idx;
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guint fd_in_tag;
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QemuOpts *opts;
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bool replay;
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22
qemu-char.c
22
qemu-char.c
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@ -165,6 +165,7 @@ CharDriverState *qemu_chr_alloc(ChardevCommon *backend, Error **errp)
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CharDriverState *chr = g_malloc0(sizeof(CharDriverState));
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qemu_mutex_init(&chr->chr_write_lock);
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chr->mux_idx = -1;
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if (backend->has_logfile) {
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int flags = O_WRONLY | O_CREAT;
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if (backend->has_logappend &&
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@ -738,17 +739,25 @@ static void mux_chr_update_read_handler(CharDriverState *chr,
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GMainContext *context)
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{
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MuxDriver *d = chr->opaque;
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int idx;
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if (d->mux_cnt >= MAX_MUX) {
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fprintf(stderr, "Cannot add I/O handlers, MUX array is full\n");
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return;
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}
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d->ext_opaque[d->mux_cnt] = chr->handler_opaque;
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d->chr_can_read[d->mux_cnt] = chr->chr_can_read;
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d->chr_read[d->mux_cnt] = chr->chr_read;
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d->chr_event[d->mux_cnt] = chr->chr_event;
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if (chr->mux_idx == -1) {
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chr->mux_idx = d->mux_cnt++;
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}
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idx = chr->mux_idx;
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d->ext_opaque[idx] = chr->handler_opaque;
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d->chr_can_read[idx] = chr->chr_can_read;
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d->chr_read[idx] = chr->chr_read;
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d->chr_event[idx] = chr->chr_event;
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/* Fix up the real driver with mux routines */
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if (d->mux_cnt == 0) {
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if (d->mux_cnt == 1) {
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qemu_chr_add_handlers_full(d->drv, mux_chr_can_read,
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mux_chr_read,
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mux_chr_event,
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@ -757,8 +766,7 @@ static void mux_chr_update_read_handler(CharDriverState *chr,
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if (d->focus != -1) {
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mux_chr_send_event(d, d->focus, CHR_EVENT_MUX_OUT);
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}
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d->focus = d->mux_cnt;
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d->mux_cnt++;
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d->focus = idx;
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mux_chr_send_event(d, d->focus, CHR_EVENT_MUX_IN);
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}
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