In the Linux kernel, the following vulnerability has been resolved: smb: client: fix use-before...

In the Linux kernel, the following vulnerability has been resolved:

smb: client: fix use-before-check of ReparseDataLength in reparse_buf_ptr()

reparse_buf_ptr() reads buf->ReparseDataLength before checking that count covers the full fixed header:

buf = (struct reparse_data_buffer *)((u8 *)io + off);
len = sizeof(*buf);                          /* 8 bytes */
rdlen = le16_to_cpu(buf->ReparseDataLength); /* offset 4, 2 bytes */

if (count < len || count < rdlen + len)      /* check comes after */

struct reparse_data_buffer has ReparseDataLength at offset 4. If a server returns OutputCount < 6, the read at offset 4-5 reaches past the end of the received data. The off+count bounds against iov_len were already validated, but that does not protect against count being smaller than sizeof(*buf).

Split the check: verify count >= sizeof(*buf) before reading ReparseDataLength, then verify count covers the data region.