[lvc-project] [PATCH 6.1] ksmbd: validate EaNameLength in smb2_get_ea()

[Votokina Victoria]

From: Victoria Votokina <Victoria.Votokina at kaspersky.com>

commit 66751841212c2cc196577453c37f7774ff363f02 upstream.

smb2_get_ea() reads ea_req->EaNameLength from the client request and
passes it directly to strncmp() as the comparison length without
verifying that the length of the name really is the size of the input
buffer received.

Fix this up by properly checking the size of the name based on the value
received and the overall size of the request, to prevent a later
strncmp() call to use the length as a "trusted" size of the buffer.
Without this check, uninitialized heap values might be slowly leaked to
the client.

Cc: Namjae Jeon <linkinjeon at kernel.org>
Cc: Steve French <smfrench at gmail.com>
Cc: Sergey Senozhatsky <senozhatsky at chromium.org>
Cc: Tom Talpey <tom at talpey.com>
Cc: linux-cifs at vger.kernel.org
Cc: <stable at kernel.org>
Assisted-by: gregkh_clanker_t1000
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Acked-by: Namjae Jeon <linkinjeon at kernel.org>
Signed-off-by: Steve French <stfrench at microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Victoria Votokina <Victoria.Votokina at kaspersky.com>
---
Backport fix for CVE-2026-31612
 fs/smb/server/smb2pdu.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/smb/server/smb2pdu.c b/fs/smb/server/smb2pdu.c
index a2bb3461d65e..3574bb82fe72 100644
--- a/fs/smb/server/smb2pdu.c
+++ b/fs/smb/server/smb2pdu.c
@@ -4390,6 +4390,11 @@ static int smb2_get_ea(struct ksmbd_work *work, struct ksmbd_file *fp,
 
 		ea_req = (struct smb2_ea_info_req *)((char *)req +
 						     le16_to_cpu(req->InputBufferOffset));
+
+		if (le32_to_cpu(req->InputBufferLength) <
+		    offsetof(struct smb2_ea_info_req, name) +
+		    ea_req->EaNameLength)
+			return -EINVAL;
 	} else {
 		/* need to send all EAs, if no specific EA is requested*/
 		if (le32_to_cpu(req->Flags) & SL_RETURN_SINGLE_ENTRY)
-- 
2.43.0