FAILED: patch "[PATCH] smb: client: reject short READ responses in CIFSSMBRead()" failed to apply to 5.10-stable tree

The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y
git checkout FETCH_HEAD
git cherry-pick -x e6142a8bfc230c7263eb8b0475249c958ce49367
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026091606-quickstep-handstand-fba1@gregkh' --subject-prefix 'PATCH 5.10.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From e6142a8bfc230c7263eb8b0475249c958ce49367 Mon Sep 17 00:00:00 2001
From: Diego Oliva <[email protected]>
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.

index f8aa9e7b4bc6..be13ab37039d 100644
@@ -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;

From: Diego Oliva <[email protected]>

[ Upstream commit e6142a8bfc230c7263eb8b0475249c958ce49367 ]

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.

---
 fs/cifs/cifssmb.c | 7 +++++++
 1 file changed, 7 insertions(+)

index 67ff1669cab2a..ec003e785d201 100644
@@ -1806,6 +1806,13 @@ 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 = -EIO;
+		*nbytes = 0;
 	} else {
 		int data_length = le16_to_cpu(pSMBr->DataLengthHigh);
 		data_length = data_length << 16;

2.53.0