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cherry-pick CVE-2018-6556 fix

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from upstream's stable-3.0 branch
This commit is contained in:
Fabian Grünbichler 2018-08-07 11:39:50 +02:00
parent 2d8021b3bf
commit 3aee60181b
2 changed files with 116 additions and 0 deletions
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115
debian/patches/extra/0013-CVE-2018-6556-verify-netns-fd-in-lxc-user-nic.patch vendored Normal file
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@ -0,0 +1,115 @@
From 590b215c4f5225cfb7fb58d9c56fabd5197bfdac Mon Sep 17 00:00:00 2001
From: Christian Brauner <christian.brauner@ubuntu.com>
Date: Wed, 25 Jul 2018 19:56:54 +0200
Subject: [PATCH] CVE 2018-6556: verify netns fd in lxc-user-nic
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
(cherry picked from commit c1cf54ebf251fdbad1e971679614e81649f1c032)
Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
---
src/lxc/utils.h | 5 +++++
src/lxc/cmd/lxc_user_nic.c | 35 ++++++++++++++++++++++++++++++++---
src/lxc/utils.c | 12 ++++++++++++
3 files changed, 49 insertions(+), 3 deletions(-)
diff --git a/src/lxc/utils.h b/src/lxc/utils.h
index ed486853..4dff26ae 100644
--- a/src/lxc/utils.h
+++ b/src/lxc/utils.h
@@ -95,6 +95,10 @@
#define CGROUP2_SUPER_MAGIC 0x63677270
#endif
+#ifndef NSFS_MAGIC
+#define NSFS_MAGIC 0x6e736673
+#endif
+
/* Useful macros */
/* Maximum number for 64 bit integer is a string with 21 digits: 2^64 - 1 = 21 */
#define LXC_NUMSTRLEN64 21
@@ -580,6 +584,7 @@ extern void *must_realloc(void *orig, size_t sz);
/* __typeof__ should be safe to use with all compilers. */
typedef __typeof__(((struct statfs *)NULL)->f_type) fs_type_magic;
extern bool has_fs_type(const char *path, fs_type_magic magic_val);
+extern bool fhas_fs_type(int fd, fs_type_magic magic_val);
extern bool is_fs_type(const struct statfs *fs, fs_type_magic magic_val);
extern bool lxc_nic_exists(char *nic);
extern int lxc_make_tmpfile(char *template, bool rm);
diff --git a/src/lxc/cmd/lxc_user_nic.c b/src/lxc/cmd/lxc_user_nic.c
index ec9cd97e..c5beb6c8 100644
--- a/src/lxc/cmd/lxc_user_nic.c
+++ b/src/lxc/cmd/lxc_user_nic.c
@@ -1179,12 +1179,41 @@ int main(int argc, char *argv[])
exit(EXIT_FAILURE);
}
} else if (request == LXC_USERNIC_DELETE) {
- netns_fd = open(args.pid, O_RDONLY);
+ char opath[LXC_PROC_PID_FD_LEN];
+
+ /* Open the path with O_PATH which will not trigger an actual
+ * open(). Don't report an errno to the caller to not leak
+ * information whether the path exists or not.
+ * When stracing setuid is stripped so this is not a concern
+ * either.
+ */
+ netns_fd = open(args.pid, O_PATH | O_CLOEXEC);
if (netns_fd < 0) {
- usernic_error("Could not open \"%s\": %s\n", args.pid,
- strerror(errno));
+ usernic_error("Failed to open \"%s\"\n", args.pid);
+ exit(EXIT_FAILURE);
+ }
+
+ if (!fhas_fs_type(netns_fd, NSFS_MAGIC)) {
+ usernic_error("Path \"%s\" does not refer to a network namespace path\n", args.pid);
+ close(netns_fd);
+ exit(EXIT_FAILURE);
+ }
+
+ ret = snprintf(opath, sizeof(opath), "/proc/self/fd/%d", netns_fd);
+ if (ret < 0 || (size_t)ret >= sizeof(opath)) {
+ close(netns_fd);
+ exit(EXIT_FAILURE);
+ }
+
+ /* Now get an fd that we can use in setns() calls. */
+ ret = open(opath, O_RDONLY | O_CLOEXEC);
+ if (ret < 0) {
+ usernic_error("Failed to open \"%s\": %s\n", args.pid, strerror(errno));
+ close(netns_fd);
exit(EXIT_FAILURE);
}
+ close(netns_fd);
+ netns_fd = ret;
}
if (!create_db_dir(LXC_USERNIC_DB)) {
diff --git a/src/lxc/utils.c b/src/lxc/utils.c
index 9771b900..e6f600f9 100644
--- a/src/lxc/utils.c
+++ b/src/lxc/utils.c
@@ -2551,6 +2551,18 @@ bool has_fs_type(const char *path, fs_type_magic magic_val)
return has_type;
}
+bool fhas_fs_type(int fd, fs_type_magic magic_val)
+{
+ int ret;
+ struct statfs sb;
+
+ ret = fstatfs(fd, &sb);
+ if (ret < 0)
+ return false;
+
+ return is_fs_type(&sb, magic_val);
+}
+
bool lxc_nic_exists(char *nic)
{
#define __LXC_SYS_CLASS_NET_LEN 15 + IFNAMSIZ + 1
--
2.18.0

1
debian/patches/series vendored
View File

@ -18,3 +18,4 @@ extra/0009-apparmor-update-current-profiles.patch
extra/0010-apparmor-profile-generation.patch
extra/0011-apparmor-allow-start-container-to-change-to-lxc.patch
extra/0012-tests-add-test-for-generated-apparmor-profiles.patch
extra/0013-CVE-2018-6556-verify-netns-fd-in-lxc-user-nic.patch