cifs: fix crash querying symlinks stored as reparse-points

We never parsed/returned any data from .get_link() when the object is a windows reparse-point
containing a symlink. This results in the VFS layer oopsing accessing an uninitialized buffer:

...
[  171.407172] Call Trace:
[  171.408039]  readlink_copy+0x29/0x70
[  171.408872]  vfs_readlink+0xc1/0x1f0
[  171.409709]  ? readlink_copy+0x70/0x70
[  171.410565]  ? simple_attr_release+0x30/0x30
[  171.411446]  ? getname_flags+0x105/0x2a0
[  171.412231]  do_readlinkat+0x1b7/0x1e0
[  171.412938]  ? __ia32_compat_sys_newfstat+0x30/0x30
...

Fix this by adding code to handle these buffers and make sure we do return a valid buffer
to .get_link()

CC: Stable <stable@vger.kernel.org>
Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
This commit is contained in:
Ronnie Sahlberg 2019-06-27 14:57:02 +10:00 коммит произвёл Steve French
Родитель 4b972a01a7
Коммит 5de254dca8
2 изменённых файлов: 73 добавлений и 5 удалений

Просмотреть файл

@ -2372,6 +2372,41 @@ smb2_get_dfs_refer(const unsigned int xid, struct cifs_ses *ses,
kfree(dfs_rsp);
return rc;
}
static int
parse_reparse_symlink(struct reparse_symlink_data_buffer *symlink_buf,
u32 plen, char **target_path,
struct cifs_sb_info *cifs_sb)
{
unsigned int sub_len;
unsigned int sub_offset;
/* We only handle Symbolic Link : MS-FSCC 2.1.2.4 */
if (le32_to_cpu(symlink_buf->ReparseTag) != IO_REPARSE_TAG_SYMLINK) {
cifs_dbg(VFS, "srv returned invalid symlink buffer\n");
return -EIO;
}
sub_offset = le16_to_cpu(symlink_buf->SubstituteNameOffset);
sub_len = le16_to_cpu(symlink_buf->SubstituteNameLength);
if (sub_offset + 20 > plen ||
sub_offset + sub_len + 20 > plen) {
cifs_dbg(VFS, "srv returned malformed symlink buffer\n");
return -EIO;
}
*target_path = cifs_strndup_from_utf16(
symlink_buf->PathBuffer + sub_offset,
sub_len, true, cifs_sb->local_nls);
if (!(*target_path))
return -ENOMEM;
convert_delimiter(*target_path, '/');
cifs_dbg(FYI, "%s: target path: %s\n", __func__, *target_path);
return 0;
}
#define SMB2_SYMLINK_STRUCT_SIZE \
(sizeof(struct smb2_err_rsp) - 1 + sizeof(struct smb2_symlink_err_rsp))
@ -2401,11 +2436,13 @@ smb2_query_symlink(const unsigned int xid, struct cifs_tcon *tcon,
struct kvec close_iov[1];
struct smb2_create_rsp *create_rsp;
struct smb2_ioctl_rsp *ioctl_rsp;
char *ioctl_buf;
struct reparse_data_buffer *reparse_buf;
u32 plen;
cifs_dbg(FYI, "%s: path: %s\n", __func__, full_path);
*target_path = NULL;
if (smb3_encryption_required(tcon))
flags |= CIFS_TRANSFORM_REQ;
@ -2483,17 +2520,36 @@ smb2_query_symlink(const unsigned int xid, struct cifs_tcon *tcon,
if ((rc == 0) && (is_reparse_point)) {
/* See MS-FSCC 2.3.23 */
ioctl_buf = (char *)ioctl_rsp + le32_to_cpu(ioctl_rsp->OutputOffset);
reparse_buf = (struct reparse_data_buffer *)
((char *)ioctl_rsp +
le32_to_cpu(ioctl_rsp->OutputOffset));
plen = le32_to_cpu(ioctl_rsp->OutputCount);
if (plen + le32_to_cpu(ioctl_rsp->OutputOffset) >
rsp_iov[1].iov_len) {
cifs_dbg(VFS, "srv returned invalid ioctl length: %d\n", plen);
cifs_dbg(VFS, "srv returned invalid ioctl len: %d\n",
plen);
rc = -EIO;
goto querty_exit;
}
/* Do stuff with ioctl_buf/plen */
if (plen < 8) {
cifs_dbg(VFS, "reparse buffer is too small. Must be "
"at least 8 bytes but was %d\n", plen);
rc = -EIO;
goto querty_exit;
}
if (plen < le16_to_cpu(reparse_buf->ReparseDataLength) + 8) {
cifs_dbg(VFS, "srv returned invalid reparse buf "
"length: %d\n", plen);
rc = -EIO;
goto querty_exit;
}
rc = parse_reparse_symlink(
(struct reparse_symlink_data_buffer *)reparse_buf,
plen, target_path, cifs_sb);
goto querty_exit;
}

Просмотреть файл

@ -914,7 +914,19 @@ struct reparse_mount_point_data_buffer {
__u8 PathBuffer[0]; /* Variable Length */
} __packed;
/* See MS-FSCC 2.1.2.4 and cifspdu.h for struct reparse_symlink_data */
#define SYMLINK_FLAG_RELATIVE 0x00000001
struct reparse_symlink_data_buffer {
__le32 ReparseTag;
__le16 ReparseDataLength;
__u16 Reserved;
__le16 SubstituteNameOffset;
__le16 SubstituteNameLength;
__le16 PrintNameOffset;
__le16 PrintNameLength;
__le32 Flags;
__u8 PathBuffer[0]; /* Variable Length */
} __packed;
/* See MS-FSCC 2.1.2.6 and cifspdu.h for struct reparse_posix_data */