File 0373-9pfs-local-lgetxattr-don-t-follow-s.patch of Package qemu.8405
From e94399bca4059fb42a6c42e2fe0d9249805c4dc3 Mon Sep 17 00:00:00 2001
From: Greg Kurz <groug@kaod.org>
Date: Sun, 26 Feb 2017 23:42:26 +0100
Subject: [PATCH] 9pfs: local: lgetxattr: don't follow symlinks
The local_lgetxattr() callback is vulnerable to symlink attacks because
it calls lgetxattr() which follows symbolic links in all path elements but
the rightmost one.
This patch introduces a helper to emulate the non-existing fgetxattrat()
function: it is implemented with /proc/self/fd which provides a trusted
path that can be safely passed to lgetxattr().
local_lgetxattr() is converted to use this helper and opendir_nofollow().
This partly fixes CVE-2016-9602.
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
(cherry picked from commit 56ad3e54dad6cdcee8668d170df161d89581846f)
[BR: Fix and/or infrastructure for BSC#1020427 CVE-2016-9602]
Signed-off-by: Bruce Rogers <brogers@suse.com>
---
hw/9pfs/9p-posix-acl.c | 16 ++--------------
hw/9pfs/9p-util.c | 12 ++++++++++++
hw/9pfs/9p-util.h | 2 ++
hw/9pfs/9p-xattr-user.c | 8 +-------
hw/9pfs/9p-xattr.c | 31 ++++++++++++++++++++++++-------
hw/9pfs/9p-xattr.h | 2 ++
6 files changed, 43 insertions(+), 28 deletions(-)
diff --git a/hw/9pfs/9p-posix-acl.c b/hw/9pfs/9p-posix-acl.c
index 15b056d9f4..43f9646182 100644
--- a/hw/9pfs/9p-posix-acl.c
+++ b/hw/9pfs/9p-posix-acl.c
@@ -25,13 +25,7 @@
static ssize_t mp_pacl_getxattr(FsContext *ctx, const char *path,
const char *name, void *value, size_t size)
{
- char *buffer;
- ssize_t ret;
-
- buffer = rpath(ctx, path);
- ret = lgetxattr(buffer, MAP_ACL_ACCESS, value, size);
- g_free(buffer);
- return ret;
+ return local_getxattr_nofollow(ctx, path, MAP_ACL_ACCESS, value, size);
}
static ssize_t mp_pacl_listxattr(FsContext *ctx, const char *path,
@@ -89,13 +83,7 @@ static int mp_pacl_removexattr(FsContext *ctx,
static ssize_t mp_dacl_getxattr(FsContext *ctx, const char *path,
const char *name, void *value, size_t size)
{
- char *buffer;
- ssize_t ret;
-
- buffer = rpath(ctx, path);
- ret = lgetxattr(buffer, MAP_ACL_DEFAULT, value, size);
- g_free(buffer);
- return ret;
+ return local_getxattr_nofollow(ctx, path, MAP_ACL_DEFAULT, value, size);
}
static ssize_t mp_dacl_listxattr(FsContext *ctx, const char *path,
diff --git a/hw/9pfs/9p-util.c b/hw/9pfs/9p-util.c
index f8d47aa271..a8db449592 100644
--- a/hw/9pfs/9p-util.c
+++ b/hw/9pfs/9p-util.c
@@ -19,6 +19,7 @@
#include <assert.h>
#include "glib-compat.h"
#include "qemu/osdep.h"
+#include "qemu/xattr.h"
#include "9p-util.h"
int relative_openat_nofollow(int dirfd, const char *path, int flags,
@@ -63,3 +64,14 @@ int relative_openat_nofollow(int dirfd, const char *path, int flags,
return fd;
}
+
+ssize_t fgetxattrat_nofollow(int dirfd, const char *filename, const char *name,
+ void *value, size_t size)
+{
+ char *proc_path = g_strdup_printf("/proc/self/fd/%d/%s", dirfd, filename);
+ int ret;
+
+ ret = lgetxattr(proc_path, name, value, size);
+ g_free(proc_path);
+ return ret;
+}
diff --git a/hw/9pfs/9p-util.h b/hw/9pfs/9p-util.h
index e80b5a551d..676641f7c0 100644
--- a/hw/9pfs/9p-util.h
+++ b/hw/9pfs/9p-util.h
@@ -46,5 +46,7 @@ static inline int openat_file(int dirfd, const char *name, int flags,
int relative_openat_nofollow(int dirfd, const char *path, int flags,
mode_t mode);
+ssize_t fgetxattrat_nofollow(int dirfd, const char *path, const char *name,
+ void *value, size_t size);
#endif
diff --git a/hw/9pfs/9p-xattr-user.c b/hw/9pfs/9p-xattr-user.c
index c490ec3bf0..6e9d9da974 100644
--- a/hw/9pfs/9p-xattr-user.c
+++ b/hw/9pfs/9p-xattr-user.c
@@ -20,9 +20,6 @@
static ssize_t mp_user_getxattr(FsContext *ctx, const char *path,
const char *name, void *value, size_t size)
{
- char *buffer;
- ssize_t ret;
-
if (strncmp(name, "user.virtfs.", 12) == 0) {
/*
* Don't allow fetch of user.virtfs namesapce
@@ -31,10 +28,7 @@ static ssize_t mp_user_getxattr(FsContext *ctx, const char *path,
errno = ENOATTR;
return -1;
}
- buffer = rpath(ctx, path);
- ret = lgetxattr(buffer, name, value, size);
- g_free(buffer);
- return ret;
+ return local_getxattr_nofollow(ctx, path, name, value, size);
}
static ssize_t mp_user_listxattr(FsContext *ctx, const char *path,
diff --git a/hw/9pfs/9p-xattr.c b/hw/9pfs/9p-xattr.c
index f593e1aca5..cab0ee0bc3 100644
--- a/hw/9pfs/9p-xattr.c
+++ b/hw/9pfs/9p-xattr.c
@@ -14,6 +14,8 @@
#include "9p.h"
#include "fsdev/file-op-9p.h"
#include "9p-xattr.h"
+#include "9p-util.h"
+#include "9p-local.h"
static XattrOperations *get_xattr_operations(XattrOperations **h,
@@ -142,18 +144,33 @@ int v9fs_remove_xattr(FsContext *ctx,
}
-ssize_t pt_getxattr(FsContext *ctx, const char *path, const char *name,
- void *value, size_t size)
+ssize_t local_getxattr_nofollow(FsContext *ctx, const char *path,
+ const char *name, void *value, size_t size)
{
- char *buffer;
- ssize_t ret;
+ char *dirpath = g_path_get_dirname(path);
+ char *filename = g_path_get_basename(path);
+ int dirfd;
+ ssize_t ret = -1;
+
+ dirfd = local_opendir_nofollow(ctx, dirpath);
+ if (dirfd == -1) {
+ goto out;
+ }
- buffer = rpath(ctx, path);
- ret = lgetxattr(buffer, name, value, size);
- g_free(buffer);
+ ret = fgetxattrat_nofollow(dirfd, filename, name, value, size);
+ close_preserve_errno(dirfd);
+out:
+ g_free(dirpath);
+ g_free(filename);
return ret;
}
+ssize_t pt_getxattr(FsContext *ctx, const char *path, const char *name,
+ void *value, size_t size)
+{
+ return local_getxattr_nofollow(ctx, path, name, value, size);
+}
+
int pt_setxattr(FsContext *ctx, const char *path, const char *name, void *value,
size_t size, int flags)
{
diff --git a/hw/9pfs/9p-xattr.h b/hw/9pfs/9p-xattr.h
index e3ee5fa91e..d9d7ce15b2 100644
--- a/hw/9pfs/9p-xattr.h
+++ b/hw/9pfs/9p-xattr.h
@@ -28,6 +28,8 @@ typedef struct xattr_operations
const char *path, const char *name);
} XattrOperations;
+ssize_t local_getxattr_nofollow(FsContext *ctx, const char *path,
+ const char *name, void *value, size_t size);
extern XattrOperations mapped_user_xattr;
extern XattrOperations passthrough_user_xattr;
