ksmbd: fix slab out of bounds write in smb_inherit_dacl()

slab out-of-bounds write is caused by that offsets is bigger than pntsd
allocation size. This patch add the check to validate 3 offsets using
allocation size.

Reported-by: [email protected] # ZDI-CAN-22271
Cc: [email protected]
Signed-off-by: Namjae Jeon <[email protected]>
Signed-off-by: Steve French <[email protected]>

Author: namjaejeon

fs/smb/server/smbacl.c

@@ -1107,6 +1107,7 @@ int smb_inherit_dacl(struct ksmbd_conn *conn,
 		struct smb_acl *pdacl;
 		struct smb_sid *powner_sid = NULL, *pgroup_sid = NULL;
 		int powner_sid_size = 0, pgroup_sid_size = 0, pntsd_size;
+		int pntsd_alloc_size;
 
 		if (parent_pntsd->osidoffset) {
 			powner_sid = (struct smb_sid *)((char *)parent_pntsd +
@@ -1119,9 +1120,10 @@ int smb_inherit_dacl(struct ksmbd_conn *conn,
 			pgroup_sid_size = 1 + 1 + 6 + (pgroup_sid->num_subauth * 4);
 		}
 
-		pntsd = kzalloc(sizeof(struct smb_ntsd) + powner_sid_size +
-				pgroup_sid_size + sizeof(struct smb_acl) +
-				nt_size, GFP_KERNEL);
+		pntsd_alloc_size = sizeof(struct smb_ntsd) + powner_sid_size +
+			pgroup_sid_size + sizeof(struct smb_acl) + nt_size;
+
+		pntsd = kzalloc(pntsd_alloc_size, GFP_KERNEL);
 		if (!pntsd) {
 			rc = -ENOMEM;
 			goto free_aces_base;
@@ -1136,6 +1138,27 @@ int smb_inherit_dacl(struct ksmbd_conn *conn,
 		pntsd->gsidoffset = parent_pntsd->gsidoffset;
 		pntsd->dacloffset = parent_pntsd->dacloffset;
 
+		if ((u64)le32_to_cpu(pntsd->osidoffset) + powner_sid_size >
+		    pntsd_alloc_size) {
+			rc = -EINVAL;
+			kfree(pntsd);
+			goto free_aces_base;
+		}
+
+		if ((u64)le32_to_cpu(pntsd->gsidoffset) + pgroup_sid_size >
+		    pntsd_alloc_size) {
+			rc = -EINVAL;
+			kfree(pntsd);
+			goto free_aces_base;
+		}
+
+		if ((u64)le32_to_cpu(pntsd->dacloffset) + sizeof(struct smb_acl) + nt_size >
+		    pntsd_alloc_size) {
+			rc = -EINVAL;
+			kfree(pntsd);
+			goto free_aces_base;
+		}
+
 		if (pntsd->osidoffset) {
 			struct smb_sid *owner_sid = (struct smb_sid *)((char *)pntsd +
 					le32_to_cpu(pntsd->osidoffset));