From 05f78e6cf34ea3a285053bd5999e08e8ac298bd5 Mon Sep 17 00:00:00 2001 From: Frank Sorenson Date: Mon, 17 Aug 2026 12:16:57 -0500 Subject: [PATCH] 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. Fixes: a158bb66b137 ("smb: client: optimise reparse point querying") Cc: stable@vger.kernel.org Signed-off-by: Frank Sorenson Signed-off-by: Namjae Jeon Signed-off-by: Paulo Alcantara --- fs/smb/client/smb2inode.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/fs/smb/client/smb2inode.c b/fs/smb/client/smb2inode.c index bcaa44814b71..98ea5c6c34af 100644 --- a/fs/smb/client/smb2inode.c +++ b/fs/smb/client/smb2inode.c @@ -41,9 +41,11 @@ static struct reparse_data_buffer *reparse_buf_ptr(struct kvec *iov) buf = (struct reparse_data_buffer *)((u8 *)io + off); len = sizeof(*buf); - rdlen = le16_to_cpu(buf->ReparseDataLength); + if (count < len) + return ERR_PTR(smb_EIO2(smb_eio_trace_reparse_rdlen, count, 0)); - if (count < len || count < rdlen + len) + rdlen = le16_to_cpu(buf->ReparseDataLength); + if (count < rdlen + len) return ERR_PTR(smb_EIO2(smb_eio_trace_reparse_rdlen, count, rdlen)); return buf; }