smb/client: fix out-of-bounds read in symlink_data()

Since smb2_check_message() returns success without length validation for
the symlink error response, in symlink_data() it is possible for
iov->iov_len to be smaller than sizeof(struct smb2_err_rsp). If the buffer
only contains the base SMB2 header (64 bytes), accessing
err->ErrorContextCount (at offset 66) or err->ByteCount later in
symlink_data() will cause an out-of-bounds read.

Link: https://lore.kernel.org/linux-cifs/297d8d9b-adf7-42fd-a1c2-5b1f230032bc@chenxiaosong.com/
Fixes: 76894f3e2f71 ("cifs: improve symlink handling for smb2+")
Cc: Stable@vger.kernel.org
Signed-off-by: Zisen Ye <zisenye@stu.xidian.edu.cn>
Reviewed-by: ChenXiaoSong <chenxiaosong@kylinos.cn>
Signed-off-by: Steve French <stfrench@microsoft.com>

diff --git a/fs/smb/client/smb2misc.c b/fs/smb/client/smb2misc.c
index 973fce3c959c4b48fd1e9bff07855ad232344ad7..2a7355ce1a07835bc0aea644fac25d3f5171230c 100644 (file)
--- a/fs/smb/client/smb2misc.c
+++ b/fs/smb/client/smb2misc.c
@@ -241,7 +241,8 @@ smb2_check_message(char *buf, unsigned int pdu_len, unsigned int len,
        if (len != calc_len) {
                /* create failed on symlink */
                if (command == SMB2_CREATE_HE &&
-                   shdr->Status == STATUS_STOPPED_ON_SYMLINK)
+                   shdr->Status == STATUS_STOPPED_ON_SYMLINK &&
+                   len > calc_len)
                        return 0;
                /* Windows 7 server returns 24 bytes more */
                if (calc_len + 24 == len && command == SMB2_OPLOCK_BREAK_HE)