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72f0d0bf51
The local_lremovexattr() callback is vulnerable to symlink attacks because it calls lremovexattr() which follows symbolic links in all path elements but the rightmost one. This patch introduces a helper to emulate the non-existing fremovexattrat() function: it is implemented with /proc/self/fd which provides a trusted path that can be safely passed to lremovexattr(). local_lremovexattr() 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>
110 lines
2.8 KiB
C
110 lines
2.8 KiB
C
/*
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* 9p user. xattr callback
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*
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* Copyright IBM, Corp. 2010
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*
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* Authors:
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* Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2. See
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* the COPYING file in the top-level directory.
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*
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*/
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#include "qemu/osdep.h"
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#include "9p.h"
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#include "fsdev/file-op-9p.h"
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#include "9p-xattr.h"
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static ssize_t mp_user_getxattr(FsContext *ctx, const char *path,
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const char *name, void *value, size_t size)
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{
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if (strncmp(name, "user.virtfs.", 12) == 0) {
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/*
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* Don't allow fetch of user.virtfs namesapce
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* in case of mapped security
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*/
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errno = ENOATTR;
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return -1;
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}
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return local_getxattr_nofollow(ctx, path, name, value, size);
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}
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static ssize_t mp_user_listxattr(FsContext *ctx, const char *path,
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char *name, void *value, size_t size)
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{
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int name_size = strlen(name) + 1;
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if (strncmp(name, "user.virtfs.", 12) == 0) {
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/* check if it is a mapped posix acl */
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if (strncmp(name, "user.virtfs.system.posix_acl_", 29) == 0) {
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/* adjust the name and size */
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name += 12;
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name_size -= 12;
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} else {
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/*
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* Don't allow fetch of user.virtfs namesapce
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* in case of mapped security
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*/
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return 0;
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}
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}
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if (!value) {
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return name_size;
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}
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if (size < name_size) {
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errno = ERANGE;
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return -1;
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}
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/* name_size includes the trailing NUL. */
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memcpy(value, name, name_size);
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return name_size;
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}
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static int mp_user_setxattr(FsContext *ctx, const char *path, const char *name,
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void *value, size_t size, int flags)
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{
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if (strncmp(name, "user.virtfs.", 12) == 0) {
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/*
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* Don't allow fetch of user.virtfs namesapce
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* in case of mapped security
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*/
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errno = EACCES;
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return -1;
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}
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return local_setxattr_nofollow(ctx, path, name, value, size, flags);
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}
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static int mp_user_removexattr(FsContext *ctx,
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const char *path, const char *name)
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{
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if (strncmp(name, "user.virtfs.", 12) == 0) {
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/*
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* Don't allow fetch of user.virtfs namesapce
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* in case of mapped security
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*/
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errno = EACCES;
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return -1;
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}
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return local_removexattr_nofollow(ctx, path, name);
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}
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XattrOperations mapped_user_xattr = {
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.name = "user.",
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.getxattr = mp_user_getxattr,
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.setxattr = mp_user_setxattr,
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.listxattr = mp_user_listxattr,
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.removexattr = mp_user_removexattr,
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};
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XattrOperations passthrough_user_xattr = {
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.name = "user.",
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.getxattr = pt_getxattr,
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.setxattr = pt_setxattr,
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.listxattr = pt_listxattr,
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.removexattr = pt_removexattr,
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};
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