FAILED: patch "[PATCH] smb: client: reject a tree connect response whose byte count" failed to apply to 5.15-stable tree

FAILED: patch "[PATCH] smb: client: reject a tree connect response whose byte count" failed to apply to 5.15-stable tree

[gregkh]

The patch below does not apply to the 5.15-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 <stable@vger.kernel.org>.

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-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 65deb18359341141d37dc86fc7853511be3c87a7
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026090337-dismiss-carload-0d51@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From 65deb18359341141d37dc86fc7853511be3c87a7 Mon Sep 17 00:00:00 2001
From: Bryam Vargas <hexlabsecurity@proton.me>
Date: Fri, 21 Aug 2026 07:36:16 -0500
Subject: [PATCH] smb: client: reject a tree connect response whose byte count
 is too small

CIFSTCon() bounds its strnlen() over the byte area with the server's
ByteCount minus two, which for ByteCount 0 or 1 goes negative as an int
and converts to a huge size_t.  The later subtraction wraps the __u16
bytes_left, and that is what bounds cifs_strndup_from_utf16(): a bound of
up to 65535 against a ~16 KB cifs_req_poolp object runs off the end of the
slab object, and the bytes reach userspace through tcon->nativeFileSystem
in /proc/fs/cifs/DebugData.

Reject a byte area too small for what the parser consumes.  Two bytes is
the least it can consume, and no conformant response carries fewer.  The
new trace point is the 129th smb_eio_trace entry, which __mode(byte)
cannot represent, so the attribute goes with it.

Fixes: cc20c031bb06 ("cifs: convert CIFSTCon to use new unicode helper functions")
Cc: stable@vger.kernel.org
Signed-off-by: Bryam Vargas <hexlabsecurity@proton.me>
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>

diff --git a/fs/smb/client/cifssmb.c b/fs/smb/client/cifssmb.c
index 1f77512252e7..f5aad5f61dce 100644
--- a/fs/smb/client/cifssmb.c
+++ b/fs/smb/client/cifssmb.c
@@ -615,6 +615,11 @@ CIFSTCon(const unsigned int xid, struct cifs_ses *ses,
 		tcon->tid = smb_buffer_response->Tid;
 		bcc_ptr = pByteArea(smb_buffer_response);
 		bytes_left = get_bcc(smb_buffer_response);
+		if (bytes_left < 2) {
+			rc = smb_EIO2(smb_eio_trace_tcon_bcc_too_small,
+				      bytes_left, 2);
+			goto out;
+		}
 		length = strnlen(bcc_ptr, bytes_left - 2);
 		if (smb_buffer->Flags2 & SMBFLG2_UNICODE)
 			is_unicode = true;
@@ -670,6 +675,7 @@ CIFSTCon(const unsigned int xid, struct cifs_ses *ses,
 			reset_cifs_unix_caps(xid, tcon, NULL, NULL);
 		}
 	}
+out:
 	cifs_buf_release(smb_buffer);
 	return rc;
 }
diff --git a/fs/smb/client/trace.h b/fs/smb/client/trace.h
index 5b21ad3c15fb..12241abb8e2e 100644
--- a/fs/smb/client/trace.h
+++ b/fs/smb/client/trace.h
@@ -133,6 +133,7 @@
 	EM(smb_eio_trace_sym_slash,			"sym_slash") \
 	EM(smb_eio_trace_sym_target_len,		"sym_target_len") \
 	EM(smb_eio_trace_symlink_file_size,		"symlink_file_size") \
+	EM(smb_eio_trace_tcon_bcc_too_small,		"tcon_bcc_too_small") \
 	EM(smb_eio_trace_tdis_in_reconnect,		"tdis_in_reconnect") \
 	EM(smb_eio_trace_tx_chained_async,		"tx_chained_async") \
 	EM(smb_eio_trace_tx_compress_failed,		"tx_compress_failed") \
@@ -213,7 +214,7 @@
 #define EM(a, b) a,
 #define E_(a, b) a
 
-enum smb_eio_trace		{ smb_eio_traces } __mode(byte);
+enum smb_eio_trace		{ smb_eio_traces };
 enum smb3_rw_credits_trace	{ smb3_rw_credits_traces } __mode(byte);
 enum smb3_tcon_ref_trace	{ smb3_tcon_ref_traces } __mode(byte);
 

[PATCH 5.15.y 1/2] cifs: SMB1 split: connect.c

[Sasha Levin]

From: David Howells <dhowells@redhat.com>

[ Upstream commit 88f7d7e32d9e086ba87c6b04a9ba57f3f41268bd ]

Split SMB1-specific connection management stuff to smb1ops.c and move
CIFSTCon() to cifssmb.c.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Steve French <sfrench@samba.org>
cc: Paulo Alcantara <pc@manguebit.org>
cc: Enzo Matsumiya <ematsumiya@suse.de>
cc: linux-cifs@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-kernel@vger.kernel.org
Acked-by: Enzo Matsumiya <ematsumiya@suse.de>
Signed-off-by: Steve French <stfrench@microsoft.com>

[ sashal: Reduced backport -- upstream 88f7d7e32d9e0 touches 5 file(s), this
  backport carries 2. Not backported here:
  fs/smb/client/cifsproto.h
  fs/smb/client/cifssmb.c
  fs/smb/client/connect.c
  fs/smb/client/smb1ops.c
  fs/smb/client/smb1proto.h
  This note is generated from the file lists only; see the resolution record
  for the reasoning. ]

Stable-dep-of: 65deb1835934 ("smb: client: reject a tree connect response whose byte count is too small")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/cifs/cifssmb.c | 128 +++++++++++++++++++++++++++++++++++++++++++++
 fs/cifs/connect.c | 129 ----------------------------------------------
 2 files changed, 128 insertions(+), 129 deletions(-)

diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index 11a400663b9f2..5b58e198c2f0e 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -582,6 +582,134 @@ CIFSSMBNegotiate(const unsigned int xid, struct cifs_ses *ses)
 	return rc;
 }
 
+/*
+ * Issue a TREE_CONNECT request.
+ */
+int
+CIFSTCon(const unsigned int xid, struct cifs_ses *ses,
+	 const char *tree, struct cifs_tcon *tcon,
+	 const struct nls_table *nls_codepage)
+{
+	struct smb_hdr *smb_buffer;
+	struct smb_hdr *smb_buffer_response;
+	TCONX_REQ *pSMB;
+	TCONX_RSP *pSMBr;
+	unsigned char *bcc_ptr;
+	int rc = 0;
+	int length;
+	__u16 bytes_left, count;
+
+	if (ses == NULL)
+		return -EIO;
+
+	smb_buffer = cifs_buf_get();
+	if (smb_buffer == NULL)
+		return -ENOMEM;
+
+	smb_buffer_response = smb_buffer;
+
+	header_assemble(smb_buffer, SMB_COM_TREE_CONNECT_ANDX,
+			NULL /*no tid */ , 4 /*wct */ );
+
+	smb_buffer->Mid = get_next_mid(ses->server);
+	smb_buffer->Uid = ses->Suid;
+	pSMB = (TCONX_REQ *) smb_buffer;
+	pSMBr = (TCONX_RSP *) smb_buffer_response;
+
+	pSMB->AndXCommand = 0xFF;
+	pSMB->Flags = cpu_to_le16(TCON_EXTENDED_SECINFO);
+	bcc_ptr = &pSMB->Password[0];
+
+	pSMB->PasswordLength = cpu_to_le16(1);	/* minimum */
+	*bcc_ptr = 0; /* password is null byte */
+	bcc_ptr++;              /* skip password */
+	/* already aligned so no need to do it below */
+
+	if (ses->server->sign)
+		smb_buffer->Flags2 |= SMBFLG2_SECURITY_SIGNATURE;
+
+	if (ses->capabilities & CAP_STATUS32) {
+		smb_buffer->Flags2 |= SMBFLG2_ERR_STATUS;
+	}
+	if (ses->capabilities & CAP_DFS) {
+		smb_buffer->Flags2 |= SMBFLG2_DFS;
+	}
+	if (ses->capabilities & CAP_UNICODE) {
+		smb_buffer->Flags2 |= SMBFLG2_UNICODE;
+		length =
+		    cifs_strtoUTF16((__le16 *) bcc_ptr, tree,
+			6 /* max utf8 char length in bytes */ *
+			(/* server len*/ + 256 /* share len */), nls_codepage);
+		bcc_ptr += 2 * length;	/* convert num 16 bit words to bytes */
+		bcc_ptr += 2;	/* skip trailing null */
+	} else {		/* ASCII */
+		strcpy(bcc_ptr, tree);
+		bcc_ptr += strlen(tree) + 1;
+	}
+	strcpy(bcc_ptr, "?????");
+	bcc_ptr += strlen("?????");
+	bcc_ptr += 1;
+	count = bcc_ptr - &pSMB->Password[0];
+	be32_add_cpu(&pSMB->hdr.smb_buf_length, count);
+	pSMB->ByteCount = cpu_to_le16(count);
+
+	rc = SendReceive(xid, ses, smb_buffer, smb_buffer_response, &length,
+			 0);
+
+	/* above now done in SendReceive */
+	if (rc == 0) {
+		bool is_unicode;
+
+		tcon->tidStatus = CifsGood;
+		tcon->need_reconnect = false;
+		tcon->tid = smb_buffer_response->Tid;
+		bcc_ptr = pByteArea(smb_buffer_response);
+		bytes_left = get_bcc(smb_buffer_response);
+		length = strnlen(bcc_ptr, bytes_left - 2);
+		if (smb_buffer->Flags2 & SMBFLG2_UNICODE)
+			is_unicode = true;
+		else
+			is_unicode = false;
+
+
+		/* skip service field (NB: this field is always ASCII) */
+		if (length == 3) {
+			if ((bcc_ptr[0] == 'I') && (bcc_ptr[1] == 'P') &&
+			    (bcc_ptr[2] == 'C')) {
+				cifs_dbg(FYI, "IPC connection\n");
+				tcon->ipc = true;
+				tcon->pipe = true;
+			}
+		} else if (length == 2) {
+			if ((bcc_ptr[0] == 'A') && (bcc_ptr[1] == ':')) {
+				/* the most common case */
+				cifs_dbg(FYI, "disk share connection\n");
+			}
+		}
+		bcc_ptr += length + 1;
+		bytes_left -= (length + 1);
+		strlcpy(tcon->treeName, tree, sizeof(tcon->treeName));
+
+		/* mostly informational -- no need to fail on error here */
+		kfree(tcon->nativeFileSystem);
+		tcon->nativeFileSystem = cifs_strndup_from_utf16(bcc_ptr,
+						      bytes_left, is_unicode,
+						      nls_codepage);
+
+		cifs_dbg(FYI, "nativeFileSystem=%s\n", tcon->nativeFileSystem);
+
+		if ((smb_buffer_response->WordCount == 3) ||
+				 (smb_buffer_response->WordCount == 7))
+			/* field is in same location */
+			tcon->Flags = le16_to_cpu(pSMBr->OptionalSupport);
+		else
+			tcon->Flags = 0;
+		cifs_dbg(FYI, "Tcon flags: 0x%x\n", tcon->Flags);
+	}
+	cifs_buf_release(smb_buffer);
+	return rc;
+}
+
 int
 CIFSSMBTDis(const unsigned int xid, struct cifs_tcon *tcon)
 {
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index d35474b836007..12205e2f04cda 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -3628,135 +3628,6 @@ int cifs_mount(struct cifs_sb_info *cifs_sb, struct smb3_fs_context *ctx)
 }
 #endif
 
-/*
- * Issue a TREE_CONNECT request.
- */
-int
-CIFSTCon(const unsigned int xid, struct cifs_ses *ses,
-	 const char *tree, struct cifs_tcon *tcon,
-	 const struct nls_table *nls_codepage)
-{
-	struct smb_hdr *smb_buffer;
-	struct smb_hdr *smb_buffer_response;
-	TCONX_REQ *pSMB;
-	TCONX_RSP *pSMBr;
-	unsigned char *bcc_ptr;
-	int rc = 0;
-	int length;
-	__u16 bytes_left, count;
-
-	if (ses == NULL)
-		return -EIO;
-
-	smb_buffer = cifs_buf_get();
-	if (smb_buffer == NULL)
-		return -ENOMEM;
-
-	smb_buffer_response = smb_buffer;
-
-	header_assemble(smb_buffer, SMB_COM_TREE_CONNECT_ANDX,
-			NULL /*no tid */ , 4 /*wct */ );
-
-	smb_buffer->Mid = get_next_mid(ses->server);
-	smb_buffer->Uid = ses->Suid;
-	pSMB = (TCONX_REQ *) smb_buffer;
-	pSMBr = (TCONX_RSP *) smb_buffer_response;
-
-	pSMB->AndXCommand = 0xFF;
-	pSMB->Flags = cpu_to_le16(TCON_EXTENDED_SECINFO);
-	bcc_ptr = &pSMB->Password[0];
-
-	pSMB->PasswordLength = cpu_to_le16(1);	/* minimum */
-	*bcc_ptr = 0; /* password is null byte */
-	bcc_ptr++;              /* skip password */
-	/* already aligned so no need to do it below */
-
-	if (ses->server->sign)
-		smb_buffer->Flags2 |= SMBFLG2_SECURITY_SIGNATURE;
-
-	if (ses->capabilities & CAP_STATUS32) {
-		smb_buffer->Flags2 |= SMBFLG2_ERR_STATUS;
-	}
-	if (ses->capabilities & CAP_DFS) {
-		smb_buffer->Flags2 |= SMBFLG2_DFS;
-	}
-	if (ses->capabilities & CAP_UNICODE) {
-		smb_buffer->Flags2 |= SMBFLG2_UNICODE;
-		length =
-		    cifs_strtoUTF16((__le16 *) bcc_ptr, tree,
-			6 /* max utf8 char length in bytes */ *
-			(/* server len*/ + 256 /* share len */), nls_codepage);
-		bcc_ptr += 2 * length;	/* convert num 16 bit words to bytes */
-		bcc_ptr += 2;	/* skip trailing null */
-	} else {		/* ASCII */
-		strcpy(bcc_ptr, tree);
-		bcc_ptr += strlen(tree) + 1;
-	}
-	strcpy(bcc_ptr, "?????");
-	bcc_ptr += strlen("?????");
-	bcc_ptr += 1;
-	count = bcc_ptr - &pSMB->Password[0];
-	be32_add_cpu(&pSMB->hdr.smb_buf_length, count);
-	pSMB->ByteCount = cpu_to_le16(count);
-
-	rc = SendReceive(xid, ses, smb_buffer, smb_buffer_response, &length,
-			 0);
-
-	/* above now done in SendReceive */
-	if (rc == 0) {
-		bool is_unicode;
-
-		tcon->tidStatus = CifsGood;
-		tcon->need_reconnect = false;
-		tcon->tid = smb_buffer_response->Tid;
-		bcc_ptr = pByteArea(smb_buffer_response);
-		bytes_left = get_bcc(smb_buffer_response);
-		length = strnlen(bcc_ptr, bytes_left - 2);
-		if (smb_buffer->Flags2 & SMBFLG2_UNICODE)
-			is_unicode = true;
-		else
-			is_unicode = false;
-
-
-		/* skip service field (NB: this field is always ASCII) */
-		if (length == 3) {
-			if ((bcc_ptr[0] == 'I') && (bcc_ptr[1] == 'P') &&
-			    (bcc_ptr[2] == 'C')) {
-				cifs_dbg(FYI, "IPC connection\n");
-				tcon->ipc = true;
-				tcon->pipe = true;
-			}
-		} else if (length == 2) {
-			if ((bcc_ptr[0] == 'A') && (bcc_ptr[1] == ':')) {
-				/* the most common case */
-				cifs_dbg(FYI, "disk share connection\n");
-			}
-		}
-		bcc_ptr += length + 1;
-		bytes_left -= (length + 1);
-		strlcpy(tcon->treeName, tree, sizeof(tcon->treeName));
-
-		/* mostly informational -- no need to fail on error here */
-		kfree(tcon->nativeFileSystem);
-		tcon->nativeFileSystem = cifs_strndup_from_utf16(bcc_ptr,
-						      bytes_left, is_unicode,
-						      nls_codepage);
-
-		cifs_dbg(FYI, "nativeFileSystem=%s\n", tcon->nativeFileSystem);
-
-		if ((smb_buffer_response->WordCount == 3) ||
-			 (smb_buffer_response->WordCount == 7))
-			/* field is in same location */
-			tcon->Flags = le16_to_cpu(pSMBr->OptionalSupport);
-		else
-			tcon->Flags = 0;
-		cifs_dbg(FYI, "Tcon flags: 0x%x\n", tcon->Flags);
-	}
-
-	cifs_buf_release(smb_buffer);
-	return rc;
-}
-
 static void delayed_free(struct rcu_head *p)
 {
 	struct cifs_sb_info *cifs_sb = container_of(p, struct cifs_sb_info, rcu);
-- 
2.53.0

[PATCH 5.15.y 2/2] smb: client: reject a tree connect response whose byte count is too small

[Sasha Levin]

From: Bryam Vargas <hexlabsecurity@proton.me>

[ Upstream commit 65deb18359341141d37dc86fc7853511be3c87a7 ]

CIFSTCon() bounds its strnlen() over the byte area with the server's
ByteCount minus two, which for ByteCount 0 or 1 goes negative as an int
and converts to a huge size_t.  The later subtraction wraps the __u16
bytes_left, and that is what bounds cifs_strndup_from_utf16(): a bound of
up to 65535 against a ~16 KB cifs_req_poolp object runs off the end of the
slab object, and the bytes reach userspace through tcon->nativeFileSystem
in /proc/fs/cifs/DebugData.

Reject a byte area too small for what the parser consumes.  Two bytes is
the least it can consume, and no conformant response carries fewer.  The
new trace point is the 129th smb_eio_trace entry, which __mode(byte)
cannot represent, so the attribute goes with it.

Fixes: cc20c031bb06 ("cifs: convert CIFSTCon to use new unicode helper functions")
Cc: stable@vger.kernel.org
Signed-off-by: Bryam Vargas <hexlabsecurity@proton.me>
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
[ adapted the fs/smb/client change to fs/cifs and replaced smb_EIO2() with -EIO while omitting unavailable tracing changes. ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/cifs/cifssmb.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index 5b58e198c2f0e..31fd29dc6f8d2 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -665,6 +665,10 @@ CIFSTCon(const unsigned int xid, struct cifs_ses *ses,
 		tcon->tid = smb_buffer_response->Tid;
 		bcc_ptr = pByteArea(smb_buffer_response);
 		bytes_left = get_bcc(smb_buffer_response);
+		if (bytes_left < 2) {
+			rc = -EIO;
+			goto out;
+		}
 		length = strnlen(bcc_ptr, bytes_left - 2);
 		if (smb_buffer->Flags2 & SMBFLG2_UNICODE)
 			is_unicode = true;
@@ -706,6 +710,7 @@ CIFSTCon(const unsigned int xid, struct cifs_ses *ses,
 			tcon->Flags = 0;
 		cifs_dbg(FYI, "Tcon flags: 0x%x\n", tcon->Flags);
 	}
+out:
 	cifs_buf_release(smb_buffer);
 	return rc;
 }
-- 
2.53.0