lkml.org 
[lkml]   [2022]   [Oct]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 6.0 096/862] NFSD: Protect against send buffer overflow in NFSv3 READDIR
    Date
    From: Chuck Lever <chuck.lever@oracle.com>

    commit 640f87c190e0d1b2a0fcb2ecf6d2cd53b1c41991 upstream.

    Since before the git era, NFSD has conserved the number of pages
    held by each nfsd thread by combining the RPC receive and send
    buffers into a single array of pages. This works because there are
    no cases where an operation needs a large RPC Call message and a
    large RPC Reply message at the same time.

    Once an RPC Call has been received, svc_process() updates
    svc_rqst::rq_res to describe the part of rq_pages that can be
    used for constructing the Reply. This means that the send buffer
    (rq_res) shrinks when the received RPC record containing the RPC
    Call is large.

    A client can force this shrinkage on TCP by sending a correctly-
    formed RPC Call header contained in an RPC record that is
    excessively large. The full maximum payload size cannot be
    constructed in that case.

    Thanks to Aleksi Illikainen and Kari Hulkko for uncovering this
    issue.

    Reported-by: Ben Ronallo <Benjamin.Ronallo@synopsys.com>
    Cc: <stable@vger.kernel.org>
    Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
    Reviewed-by: Jeff Layton <jlayton@kernel.org>
    Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    fs/nfsd/nfs3proc.c | 7 ++++---
    1 file changed, 4 insertions(+), 3 deletions(-)

    --- a/fs/nfsd/nfs3proc.c
    +++ b/fs/nfsd/nfs3proc.c
    @@ -563,13 +563,14 @@ static void nfsd3_init_dirlist_pages(str
    {
    struct xdr_buf *buf = &resp->dirlist;
    struct xdr_stream *xdr = &resp->xdr;
    -
    - count = clamp(count, (u32)(XDR_UNIT * 2), svc_max_payload(rqstp));
    + unsigned int sendbuf = min_t(unsigned int, rqstp->rq_res.buflen,
    + svc_max_payload(rqstp));

    memset(buf, 0, sizeof(*buf));

    /* Reserve room for the NULL ptr & eof flag (-2 words) */
    - buf->buflen = count - XDR_UNIT * 2;
    + buf->buflen = clamp(count, (u32)(XDR_UNIT * 2), sendbuf);
    + buf->buflen -= XDR_UNIT * 2;
    buf->pages = rqstp->rq_next_page;
    rqstp->rq_next_page += (buf->buflen + PAGE_SIZE - 1) >> PAGE_SHIFT;


    \
     
     \ /
      Last update: 2022-10-19 10:47    [W:2.828 / U:0.388 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site