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

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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 <sorenson@redhat.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
This commit is contained in:
Frank Sorenson
2026-08-17 12:16:57 -05:00
committed by Paulo Alcantara
parent 62656b024e
commit 05f78e6cf3
1 changed files with 4 additions and 2 deletions
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6
fs/smb/client/smb2inode.c
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@@ -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;
}