CVE-2026-89632smb: client: fix use-before-check of ReparseDataLength in reparse_buf_ptr()

Official description

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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/b70bc592afd19732e2e4563300ebe8f974280365
• https://git.kernel.org/stable/c/711cf71300d7992f450600df8864917d3538679f
• https://git.kernel.org/stable/c/05f78e6cf34ea3a285053bd5999e08e8ac298bd5