File 0216-9pfs-local-forbid-client-access-to-.patch of Package qemu-linux-user.15026
From 95d3420f4e7a5c5630017569d29930ce52174620 Mon Sep 17 00:00:00 2001
From: Greg Kurz <groug@kaod.org>
Date: Fri, 5 May 2017 14:48:08 +0200
Subject: [PATCH] 9pfs: local: forbid client access to metadata (CVE-2017-7493)
When using the mapped-file security mode, we shouldn't let the client mess
with the metadata. The current code already tries to hide the metadata dir
from the client by skipping it in local_readdir(). But the client can still
access or modify it through several other operations. This can be used to
escalate privileges in the guest.
Affected backend operations are:
- local_mknod()
- local_mkdir()
- local_open2()
- local_symlink()
- local_link()
- local_unlinkat()
- local_renameat()
- local_rename()
- local_name_to_path()
Other operations are safe because they are only passed a fid path, which
is computed internally in local_name_to_path().
This patch converts all the functions listed above to fail and return
EINVAL when being passed the name of the metadata dir. This may look
like a poor choice for errno, but there's no such thing as an illegal
path name on Linux and I could not think of anything better.
This fixes CVE-2017-7493.
Reported-by: Leo Gaspard <leo@gaspard.io>
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
(cherry picked from commit 7a95434e0ca8a037fd8aa1a2e2461f92585eb77b)
[BR: BSC#1039495]
Signed-off-by: Bruce Rogers <brogers@suse.com>
---
hw/9pfs/9p-local.c | 58 ++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 56 insertions(+), 2 deletions(-)
diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c
index e93d48edab..9bc6956075 100644
--- a/hw/9pfs/9p-local.c
+++ b/hw/9pfs/9p-local.c
@@ -452,6 +452,11 @@ static off_t local_telldir(FsContext *ctx, V9fsFidOpenState *fs)
return telldir(fs->dir.stream);
}
+static bool local_is_mapped_file_metadata(FsContext *fs_ctx, const char *name)
+{
+ return !strcmp(name, VIRTFS_META_DIR);
+}
+
static int local_readdir_r(FsContext *ctx, V9fsFidOpenState *fs,
struct dirent *entry,
struct dirent **result)
@@ -464,8 +469,8 @@ again:
entry->d_type = DT_UNKNOWN;
} else if (ctx->export_flags & V9FS_SM_MAPPED_FILE) {
if (!ret && *result != NULL &&
- !strcmp(entry->d_name, VIRTFS_META_DIR)) {
- /* skp the meta data directory */
+ local_is_mapped_file_metadata(ctx, entry->d_name)) {
+ /* skip the meta data directory */
goto again;
}
entry->d_type = DT_UNKNOWN;
@@ -558,6 +563,12 @@ static int local_mknod(FsContext *fs_ctx, V9fsPath *dir_path,
int err = -1;
int dirfd;
+ if (fs_ctx->export_flags & V9FS_SM_MAPPED_FILE &&
+ local_is_mapped_file_metadata(fs_ctx, name)) {
+ errno = EINVAL;
+ return -1;
+ }
+
dirfd = local_opendir_nofollow(fs_ctx, dir_path->data);
if (dirfd == -1) {
return -1;
@@ -604,6 +615,12 @@ static int local_mkdir(FsContext *fs_ctx, V9fsPath *dir_path,
int err = -1;
int dirfd;
+ if (fs_ctx->export_flags & V9FS_SM_MAPPED_FILE &&
+ local_is_mapped_file_metadata(fs_ctx, name)) {
+ errno = EINVAL;
+ return -1;
+ }
+
dirfd = local_opendir_nofollow(fs_ctx, dir_path->data);
if (dirfd == -1) {
return -1;
@@ -693,6 +710,12 @@ static int local_open2(FsContext *fs_ctx, V9fsPath *dir_path, const char *name,
int err = -1;
int dirfd;
+ if (fs_ctx->export_flags & V9FS_SM_MAPPED_FILE &&
+ local_is_mapped_file_metadata(fs_ctx, name)) {
+ errno = EINVAL;
+ return -1;
+ }
+
/*
* Mark all the open to not follow symlinks
*/
@@ -751,6 +774,12 @@ static int local_symlink(FsContext *fs_ctx, const char *oldpath,
int err = -1;
int dirfd;
+ if (fs_ctx->export_flags & V9FS_SM_MAPPED_FILE &&
+ local_is_mapped_file_metadata(fs_ctx, name)) {
+ errno = EINVAL;
+ return -1;
+ }
+
dirfd = local_opendir_nofollow(fs_ctx, dir_path->data);
if (dirfd == -1) {
return -1;
@@ -825,6 +854,12 @@ static int local_link(FsContext *ctx, V9fsPath *oldpath,
int ret = -1;
int odirfd, ndirfd;
+ if (ctx->export_flags & V9FS_SM_MAPPED_FILE &&
+ local_is_mapped_file_metadata(ctx, name)) {
+ errno = EINVAL;
+ return -1;
+ }
+
odirfd = local_opendir_nofollow(ctx, odirpath);
if (odirfd == -1) {
goto out;
@@ -1095,6 +1130,12 @@ static int local_lremovexattr(FsContext *ctx, V9fsPath *fs_path,
static int local_name_to_path(FsContext *ctx, V9fsPath *dir_path,
const char *name, V9fsPath *target)
{
+ if (ctx->export_flags & V9FS_SM_MAPPED_FILE &&
+ local_is_mapped_file_metadata(ctx, name)) {
+ errno = EINVAL;
+ return -1;
+ }
+
if (dir_path) {
v9fs_path_sprintf(target, "%s/%s", dir_path->data, name);
} else if (strcmp(name, "/")) {
@@ -1115,6 +1156,13 @@ static int local_renameat(FsContext *ctx, V9fsPath *olddir,
int ret;
int odirfd, ndirfd;
+ if (ctx->export_flags & V9FS_SM_MAPPED_FILE &&
+ (local_is_mapped_file_metadata(ctx, old_name) ||
+ local_is_mapped_file_metadata(ctx, new_name))) {
+ errno = EINVAL;
+ return -1;
+ }
+
odirfd = local_opendir_nofollow(ctx, olddir->data);
if (odirfd == -1) {
return -1;
@@ -1205,6 +1253,12 @@ static int local_unlinkat(FsContext *ctx, V9fsPath *dir,
int ret;
int dirfd;
+ if (ctx->export_flags & V9FS_SM_MAPPED_FILE &&
+ local_is_mapped_file_metadata(ctx, name)) {
+ errno = EINVAL;
+ return -1;
+ }
+
dirfd = local_opendir_nofollow(ctx, dir->data);
if (dirfd == -1) {
return -1;
