From 949055a2549afc4cde06b7972072c7288bb43722 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Marc-Andr=C3=A9=20Lureau?= Date: Mon, 3 Oct 2016 13:47:04 +0400 Subject: [PATCH] char: use a fixed idx for child muxed chr MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Message-Id: <20161003094704.18087-3-marcandre.lureau@redhat.com> Signed-off-by: Paolo Bonzini --- include/sysemu/char.h | 1 + qemu-char.c | 22 +++++++++++++++------- 2 files changed, 16 insertions(+), 7 deletions(-) diff --git a/include/sysemu/char.h b/include/sysemu/char.h index 0d0465ae0e..4593576cf7 100644 --- a/include/sysemu/char.h +++ b/include/sysemu/char.h @@ -92,6 +92,7 @@ struct CharDriverState { int explicit_be_open; int avail_connections; int is_mux; + int mux_idx; guint fd_in_tag; QemuOpts *opts; bool replay; diff --git a/qemu-char.c b/qemu-char.c index fb456cec34..7a85b1f0b3 100644 --- a/qemu-char.c +++ b/qemu-char.c @@ -165,6 +165,7 @@ CharDriverState *qemu_chr_alloc(ChardevCommon *backend, Error **errp) CharDriverState *chr = g_malloc0(sizeof(CharDriverState)); qemu_mutex_init(&chr->chr_write_lock); + chr->mux_idx = -1; if (backend->has_logfile) { int flags = O_WRONLY | O_CREAT; if (backend->has_logappend && @@ -738,17 +739,25 @@ static void mux_chr_update_read_handler(CharDriverState *chr, GMainContext *context) { MuxDriver *d = chr->opaque; + int idx; if (d->mux_cnt >= MAX_MUX) { fprintf(stderr, "Cannot add I/O handlers, MUX array is full\n"); return; } - d->ext_opaque[d->mux_cnt] = chr->handler_opaque; - d->chr_can_read[d->mux_cnt] = chr->chr_can_read; - d->chr_read[d->mux_cnt] = chr->chr_read; - d->chr_event[d->mux_cnt] = chr->chr_event; + + if (chr->mux_idx == -1) { + chr->mux_idx = d->mux_cnt++; + } + + idx = chr->mux_idx; + d->ext_opaque[idx] = chr->handler_opaque; + d->chr_can_read[idx] = chr->chr_can_read; + d->chr_read[idx] = chr->chr_read; + d->chr_event[idx] = chr->chr_event; + /* Fix up the real driver with mux routines */ - if (d->mux_cnt == 0) { + if (d->mux_cnt == 1) { qemu_chr_add_handlers_full(d->drv, mux_chr_can_read, mux_chr_read, mux_chr_event, @@ -757,8 +766,7 @@ static void mux_chr_update_read_handler(CharDriverState *chr, if (d->focus != -1) { mux_chr_send_event(d, d->focus, CHR_EVENT_MUX_OUT); } - d->focus = d->mux_cnt; - d->mux_cnt++; + d->focus = idx; mux_chr_send_event(d, d->focus, CHR_EVENT_MUX_IN); } -- 2.11.4.GIT