ksmbd: fix out-of-bound read in smb2_write
ksmbd_smb2_check_message doesn't validate hdr->NextCommand. If
->NextCommand is bigger than Offset + Length of smb2 write, It will
allow oversized smb2 write length. It will cause OOB read in smb2_write.
Cc: stable@vger.kernel.org
Reported-by: zdi-disclosures@trendmicro.com # ZDI-CAN-21164
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
diff --git a/fs/smb/server/smb2misc.c b/fs/smb/server/smb2misc.c
index 57749f4..33b7e6c 100644
--- a/fs/smb/server/smb2misc.c
+++ b/fs/smb/server/smb2misc.c
@@ -351,10 +351,16 @@ int ksmbd_smb2_check_message(struct ksmbd_work *work)
int command;
__u32 clc_len; /* calculated length */
__u32 len = get_rfc1002_len(work->request_buf);
- __u32 req_struct_size;
+ __u32 req_struct_size, next_cmd = le32_to_cpu(hdr->NextCommand);
- if (le32_to_cpu(hdr->NextCommand) > 0)
- len = le32_to_cpu(hdr->NextCommand);
+ if ((u64)work->next_smb2_rcv_hdr_off + next_cmd > len) {
+ pr_err("next command(%u) offset exceeds smb msg size\n",
+ next_cmd);
+ return 1;
+ }
+
+ if (next_cmd > 0)
+ len = next_cmd;
else if (work->next_smb2_rcv_hdr_off)
len -= work->next_smb2_rcv_hdr_off;
