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[libvirt] [PATCH] lxc: Set max uid/gid mappings for user namespace



There is a limit on the number of lines in the /proc/<pid>/{g,u}id_map
files. In Linux 4.14 and earlier, this limit was (arbitrarily) set at
5 lines. Since Linux 4.15, which was released on 28 Jan 2018, the limit
is 340 lines.

This change is documented in user_namespaces(7).

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=6397fac4915ab3002dc15aae751455da1a852f25

Signed-off-by: Radostin Stoyanov <rstoyanov1 gmail com>
---
 src/lxc/lxc_controller.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/src/lxc/lxc_controller.c b/src/lxc/lxc_controller.c
index 99360397a7..2bec8846aa 100644
--- a/src/lxc/lxc_controller.c
+++ b/src/lxc/lxc_controller.c
@@ -1390,6 +1390,13 @@ virLXCControllerSetupUsernsMap(virDomainIdMapEntryPtr map,
     size_t i;
     int ret = -1;

+    /* The kernel supports up to 340 lines in /proc/<pid>/{g,u}id_map */
+    if (num > 340) {
+        virReportError(VIR_ERR_INVALID_ARG, "%s",
+                       _("Too many id mappings defined."));
+        goto cleanup;
+    }
+
     for (i = 0; i < num; i++)
         virBufferAsprintf(&map_value, "%u %u %u\n",
                           map[i].start, map[i].target, map[i].count);
--
2.19.2


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