From e6142a8bfc230c7263eb8b0475249c958ce49367 Mon Sep 17 00:00:00 2001 From: Diego Oliva Date: Wed, 2 Sep 2026 11:42:06 +0100 Subject: [PATCH] smb: client: reject short READ responses in CIFSSMBRead() CIFSSMBRead() reads DataLengthHigh, DataLength and DataOffset out of the READ_RSP returned by the server without first checking that a whole READ_RSP was actually received. The length of the response is recorded in rsp_iov.iov_len, but nothing constrains it to be at least read_rsp_size before those fields are dereferenced. A malicious or compromised SMB1 server can return a response shorter than the READ_RSP header, so that parsing the header itself reads past the end of the receive buffer. SMB1 is not negotiated by default; reaching this code requires an explicit vers=1.0 mount. Reject the response unless it is at least read_rsp_size bytes long. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Suggested-by: Paulo Alcantara Cc: stable@vger.kernel.org # 6.19.x Assisted-by: Bynario AI Signed-off-by: Diego Oliva Reviewed-by: David Howells Signed-off-by: Paulo Alcantara --- fs/smb/client/cifssmb.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/fs/smb/client/cifssmb.c b/fs/smb/client/cifssmb.c index f8aa9e7b4bc6..be13ab37039d 100644 --- a/fs/smb/client/cifssmb.c +++ b/fs/smb/client/cifssmb.c @@ -1719,6 +1719,14 @@ CIFSSMBRead(const unsigned int xid, struct cifs_io_parms *io_parms, pSMBr = (READ_RSP *)rsp_iov.iov_base; if (rc) { cifs_dbg(VFS, "Send error in read = %d\n", rc); + } else if (rsp_iov.iov_len < tcon->ses->server->vals->read_rsp_size) { + /* check that the received response can hold a whole READ_RSP */ + cifs_dbg(FYI, "%s: server returned short header. got=%zu expected=%zu\n", + __func__, rsp_iov.iov_len, + tcon->ses->server->vals->read_rsp_size); + rc = smb_EIO2(smb_eio_trace_read_rsp_short, + rsp_iov.iov_len, tcon->ses->server->vals->read_rsp_size); + *nbytes = 0; } else { int data_length = le16_to_cpu(pSMBr->DataLengthHigh); data_length = data_length << 16;