[PATCH 5.15.y] smb: client: validate SMB1 EA list bounds before parsing

[Sasha Levin <sashal@kernel.org>]

From: Ratnaker Gautam <ratnaker.gautam@kuleuven.be>

[ Upstream commit ddc7a7e1eeb116ccaf010a6f1fb6ab927f3f888d ]

CIFSSMBQAllEAs() checks the server-provided EA list length by adding it
to the response pointer. On 32-bit systems, a positive length can wrap
the pointer and pass the comparison. The parser then walks outside the
received response while reading the next FEA header.

A response with a list length of 0x40000000 reproduces this as a native
i386 page fault and kernel panic from listxattr() against an SMB1
server.

Check that the EA list starts within the SMB byte area before reading
its header. Keep its length unsigned and compare it with the bytes left
in the response without pointer addition.

SMB1 is not negotiated by default and requires an explicit vers=1.0
mount.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Ratnaker Gautam <ratnaker.gautam@kuleuven.be>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
[ sashal: Replaced unavailable smb_EIO2() calls with direct -EIO assignments. ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/cifs/cifssmb.c | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index 11a400663b9f2..1d8a35366ea7a 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -6043,9 +6043,11 @@ CIFSSMBQAllEAs(const unsigned int xid, struct cifs_tcon *tcon,
 	int rc = 0;
 	int bytes_returned;
 	int list_len;
+	u32 ea_list_len;
 	struct fealist *ea_response_data;
 	struct fea *temp_fea;
 	char *temp_ptr;
+	char *byte_area;
 	char *end_of_smb;
 	__u16 params, byte_count, data_offset;
 	unsigned int ea_name_len = ea_name ? strlen(ea_name) : 0;
@@ -6122,9 +6124,18 @@ CIFSSMBQAllEAs(const unsigned int xid, struct cifs_tcon *tcon,
 	ea_response_data = (struct fealist *)
 				(((char *) &pSMBr->hdr.Protocol) + data_offset);
 
-	list_len = le32_to_cpu(ea_response_data->list_len);
-	cifs_dbg(FYI, "ea length %d\n", list_len);
-	if (list_len <= 8) {
+	byte_area = pByteArea(&pSMBr->hdr);
+	end_of_smb = byte_area + get_bcc(&pSMBr->hdr);
+	if ((char *)ea_response_data < byte_area ||
+	    (char *)ea_response_data >
+	    end_of_smb - sizeof(ea_response_data->list_len)) {
+		rc = -EIO;
+		goto QAllEAsOut;
+	}
+
+	ea_list_len = le32_to_cpu(ea_response_data->list_len);
+	cifs_dbg(FYI, "%s: ea length: %u\n", __func__, ea_list_len);
+	if (ea_list_len <= 8) {
 		cifs_dbg(FYI, "empty EA list returned from server\n");
 		/* didn't find the named attribute */
 		if (ea_name)
@@ -6133,12 +6144,12 @@ CIFSSMBQAllEAs(const unsigned int xid, struct cifs_tcon *tcon,
 	}
 
 	/* make sure list_len doesn't go past end of SMB */
-	end_of_smb = (char *)pByteArea(&pSMBr->hdr) + get_bcc(&pSMBr->hdr);
-	if ((char *)ea_response_data + list_len > end_of_smb) {
+	if (ea_list_len > end_of_smb - (char *)ea_response_data) {
 		cifs_dbg(FYI, "EA list appears to go beyond SMB\n");
 		rc = -EIO;
 		goto QAllEAsOut;
 	}
+	list_len = ea_list_len;
 
 	/* account for ea list len */
 	list_len -= 4;
-- 
2.53.0