Re: [PATCH] qemu-ga: Fix a SIGSEGV on guest-set-time command

[Konstantin Kostiuk <kkostiuk@redhat.com>]

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Hi Sunil,

I updated the commit message according to Daniel's comment and got this
patch to merge.

Best Regards,
Konstantin Kostiuk.


On Mon, Oct 21, 2024 at 11:26 AM Daniel P. Berrangé <berrange@redhat.com>
wrote:

> On Fri, Oct 18, 2024 at 03:34:39PM +0530, Sunil Nimmagadda wrote:
> > qemu-ga on a NetBSD -current VM terminates with a SIGSEGV upon receiving
> > 'guest-set-time' command...
> >
> > Core was generated by `qemu-ga'.
> > Program terminated with signal SIGSEGV, Segmentation fault.
> > #0  0x000000000cd37a40 in ga_pipe_read_str (fd=fd@entry=0xffffff922a20,
> str=str@entry=0xffffff922a18)
> >     at ../qga/commands-posix.c:88
> > 88            *str[len] = '\0';
> > [Current thread is 1 (process 1112)]
> > (gdb) bt
> > #0  0x000000000cd37a40 in ga_pipe_read_str (fd=fd@entry=0xffffff922a20,
> str=str@entry=0xffffff922a18)
> >     at ../qga/commands-posix.c:88
> > #1  0x000000000cd37b60 in ga_run_command (argv=argv@entry=0xffffff922a90,
>
> >     action=action@entry=0xcda34b8 "set hardware clock to system time",
> errp=errp@entry=0xffffff922a70, in_str=0x0)
> >     at ../qga/commands-posix.c:164
> > #2  0x000000000cd380c4 in qmp_guest_set_time (has_time=<optimized out>,
> time_ns=<optimized out>,
> >     errp=errp@entry=0xffffff922ad0) at ../qga/commands-posix.c:304
> > #3  0x000000000cd253d8 in qmp_marshal_guest_set_time (args=<optimized
> out>, ret=<optimized out>, errp=0xffffff922b48)
> >     at qga/qga-qapi-commands.c:193
> > #4  0x000000000cd4e71c in qmp_dispatch (cmds=cmds@entry=0xcdf5b18
> <ga_commands>, request=request@entry=0xf3c711a4b000,
> >     allow_oob=allow_oob@entry=false, cur_mon=cur_mon@entry=0x0) at
> ../qapi/qmp-dispatch.c:220
> > #5  0x000000000cd36524 in process_event (opaque=0xf3c711a79000,
> obj=0xf3c711a4b000, err=0x0) at ../qga/main.c:677
> > #6  0x000000000cd526f0 in json_message_process_token (lexer=lexer@entry=0xf3c711a79018,
> input=0xf3c712072480,
> >     type=type@entry=JSON_RCURLY, x=28, y=1) at
> ../qobject/json-streamer.c:99
> > #7  0x000000000cd93860 in json_lexer_feed_char (lexer=lexer@entry=0xf3c711a79018,
> ch=125 '}', flush=flush@entry=false)
> >     at ../qobject/json-lexer.c:313
> > #8  0x000000000cd93a00 in json_lexer_feed (lexer=lexer@entry=0xf3c711a79018,
>
> >     buffer=buffer@entry=0xffffff922d10
> "{\"execute\":\"guest-set-time\"}\n", size=<optimized out>)
> >     at ../qobject/json-lexer.c:350
> > #9  0x000000000cd5290c in json_message_parser_feed (parser=parser@entry=0xf3c711a79000,
>
> >     buffer=buffer@entry=0xffffff922d10
> "{\"execute\":\"guest-set-time\"}\n", size=<optimized out>)
> >     at ../qobject/json-streamer.c:121
> > #10 0x000000000cd361fc in channel_event_cb (condition=<optimized out>,
> data=0xf3c711a79000) at ../qga/main.c:703
> > #11 0x000000000cd3710c in ga_channel_client_event (channel=<optimized
> out>, condition=<optimized out>, data=0xf3c711b2d300)
> >     at ../qga/channel-posix.c:94
> > #12 0x0000f3c7120d9bec in g_main_dispatch () from
> /usr/pkg/lib/libglib-2.0.so.0
> > #13 0x0000f3c7120dd25c in g_main_context_iterate_unlocked.constprop ()
> from /usr/pkg/lib/libglib-2.0.so.0
> > #14 0x0000f3c7120ddbf0 in g_main_loop_run () from
> /usr/pkg/lib/libglib-2.0.so.0
> > #15 0x000000000cda00d8 in run_agent_once (s=0xf3c711a79000) at
> ../qga/main.c:1522
> > #16 run_agent (s=0xf3c711a79000) at ../qga/main.c:1559
> > #17 main (argc=<optimized out>, argv=<optimized out>) at
> ../qga/main.c:1671
> > (gdb)
> >
> > The commandline options used on the host machine...
> > qemu-system-aarch64 \
> >    -machine type=virt,pflash0=rom \
> >    -m 8G \
> >    -cpu host \
> >    -smp 8 \
> >    -accel hvf \
> >    -device virtio-net-pci,netdev=unet \
> >    -device virtio-blk-pci,drive=hd \
> >    -drive file=netbsd.qcow2,if=none,id=hd \
> >    -netdev user,id=unet,hostfwd=tcp::2223-:22 \
> >    -object rng-random,filename=/dev/urandom,id=viornd0 \
> >    -device virtio-rng-pci,rng=viornd0 \
> >    -serial mon:stdio \
> >    -display none \
> >    -blockdev
> node-name=rom,driver=file,filename=/opt/homebrew/Cellar/qemu/9.0.2/share/qemu/edk2-aarch64-code.fd,read-only=true
> \
> >    -chardev socket,path=/tmp/qga_netbsd.sock,server=on,wait=off,id=qga0 \
> >    -device virtio-serial \
> >    -device virtconsole,chardev=qga0,name=org.qemu.guest_agent.0
>
> This bug isn't platform specific AFAICT, and will also hit
> other commands.
>
> Was introduced by:
>
> commit c3f32c13a325f1ca9a0b08c19fefe9e5cc04289d
> Author: Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>
> Date:   Wed Mar 20 18:16:43 2024 +0200
>
>     qga: introduce ga_run_command() helper for guest cmd execution
>
> and then affects multiple commands:
>
>     qga/commands-posix: qmp_guest_set_user_password: use ga_run_command
> helper
>     qga/commands-posix: execute_fsfreeze_hook: use ga_run_command helper
>     qga/commands-posix: qmp_guest_set_time: use ga_run_command helper
>     qga/commands-posix: qmp_guest_shutdown: use ga_run_command helper
>
> IOW, this is a regression in the 9.1.0 release
>
> >
> > This patch rectifies the operator precedence while assigning the NUL
> > terminator.
> >
> > Signed-off-by: Sunil Nimmagadda <sunil@nimmagadda.net>
> >
> > diff --git a/qga/commands-posix.c b/qga/commands-posix.c
> > index c2bd0b4..bb41fa9 100644
> > --- a/qga/commands-posix.c
> > +++ b/qga/commands-posix.c
> > @@ -85,7 +85,7 @@ static ssize_t ga_pipe_read_str(int fd[2], char **str)
> >          *str = g_realloc(*str, len + n + 1);
> >          memcpy(*str + len, buf, n);
> >          len += n;
> > -        *str[len] = '\0';
> > +        (*str)[len] = '\0';
> >      }
> >      close(fd[0]);
> >      fd[0] = -1;
>
> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
>
> With regards,
> Daniel
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