[PATCH v2] drop setting XEN_QEMU_CONSOLE_LIMIT in the environment

[James Dingwall <james-xen@dingwall.me.uk>]

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On Tue, Nov 05, 2024 at 01:57:41PM +0100, Jan Beulich wrote:
> On 05.11.2024 13:43, James Dingwall wrote:
> > Since qemu-xen-4.18.0 the corresponding code which responds to this
> > environment variable was not applied to the qemu tree.  It doesn't make
> > sense to me that it continues to be set in libxl so here's a patch
> > which removes it.
> > 
> > These are the relevant commits for various qemu tags:
> > 
> > qemu-xen-4.10.0: c349189772cec43498b0bec8a84146f10b8937af
> > qemu-xen-4.11.0: 2b033e396f4fa0981bae1213cdacd15775655a97
> > qemu-xen-4.12.0: 4f080070a9809bde857851e68a3aeff0c4b9b6a6
> > qemu-xen-4.13.0: c81d7597747f29432a0e197bf2c2109e77f2b6cf
> > qemu-xen-4.14.0: 410cc30fdc590417ae730d635bbc70257adf6750
> > qemu-xen-4.15.0: 677cbe1324c29294bb1d1b8454b3f214725e40fd
> > qemu-xen-4.16.0: b6e539830bf45e2d7a6bd86ddfdf003088b173b0
> > qemu-xen-4.17.0: 9a5e4bc76058766962ab3ff13f42c1d39a8e08d3
> > qemu-xen-4.18.0: not present
> > qemu-xen-4.19.0: not present
> > 
> > If this is approved is someone able to apply it to the tree?
> 
> Once approved, any committer will be able to. First, however, like any patch
> this one also needs a (your?) Signed-off-by:.

v2 with Signed-off-by: (and a promise I've read 'CONTRIBUTING').

Thanks,
James

(This wiki link referenced in CONTRIBUTING currently errors though:
https://wiki.xenproject.org/wiki/Submitting_Xen_Project_Patches)

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commit 7b89ea44dbcb965b6b67c8de5092ea2b95d4c6f9
Author: James Dingwall <james@dingwall.me.uk>
Date:   Tue Nov 5 11:16:20 2024 +0000

    libxl: drop setting XEN_QEMU_CONSOLE_LIMIT in the environment (XSA-180 / CVE-2014-3672)
    
    The corresponding code in the Xen qemu repository was not applied from
    qemu-xen-4.18.0.
    
    Signed-off-by: James Dingwall <james@dingwall.me.uk>

diff --git a/tools/libs/light/libxl_dm.c b/tools/libs/light/libxl_dm.c
index 1f2f5bd97a..b193a5dc37 100644
--- a/tools/libs/light/libxl_dm.c
+++ b/tools/libs/light/libxl_dm.c
@@ -638,20 +638,6 @@ int libxl__domain_device_construct_rdm(libxl__gc *gc,
     return ERROR_FAIL;
 }
 
-/* XSA-180 / CVE-2014-3672
- *
- * The QEMU shipped with Xen has a bodge. It checks for
- * XEN_QEMU_CONSOLE_LIMIT to see how much data QEMU is allowed
- * to write to stderr. We set that to 1MB if it is not set by
- * system administrator.
- */
-static void libxl__set_qemu_env_for_xsa_180(libxl__gc *gc,
-                                            flexarray_t *dm_envs)
-{
-    if (getenv("XEN_QEMU_CONSOLE_LIMIT")) return;
-    flexarray_append_pair(dm_envs, "XEN_QEMU_CONSOLE_LIMIT", "1048576");
-}
-
 const libxl_vnc_info *libxl__dm_vnc(const libxl_domain_config *guest_config)
 {
     const libxl_vnc_info *vnc = NULL;
@@ -704,8 +690,6 @@ static int libxl__build_device_model_args_old(libxl__gc *gc,
 
     assert(state->dm_monitor_fd == -1);
 
-    libxl__set_qemu_env_for_xsa_180(gc, dm_envs);
-
     flexarray_vappend(dm_args, dm,
                       "-d", GCSPRINTF("%d", domid), NULL);
 
@@ -1210,8 +1194,6 @@ static int libxl__build_device_model_args_new(libxl__gc *gc,
     dm_args = flexarray_make(gc, 16, 1);
     dm_envs = flexarray_make(gc, 16, 1);
 
-    libxl__set_qemu_env_for_xsa_180(gc, dm_envs);
-
     flexarray_vappend(dm_args, dm,
                       "-xen-domid",
                       GCSPRINTF("%d", guest_domid), NULL);
@@ -3656,7 +3638,6 @@ void libxl__spawn_qemu_xenpv_backend(libxl__egc *egc,
     flexarray_append(dm_args, NULL);
     args = (char **) flexarray_contents(dm_args);
 
-    libxl__set_qemu_env_for_xsa_180(gc, dm_envs);
     envs = (char **) flexarray_contents(dm_envs);
 
     logfile_w = libxl__create_qemu_logfile(gc, GCSPRINTF("qdisk-%u", domid));