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NFSD: Protect against send buffer overflow in NFSv2 READDIR

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Restore the previous limit on the @count argument to prevent a
buffer overflow attack.

Fixes: 53b1119a6e ("NFSD: Fix READDIR buffer overflow")
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>
This commit is contained in:
Chuck Lever 2022-09-01 15:10:05 -04:00
parent 1242a87da0
commit 00b4492686
1 changed files with 2 additions and 3 deletions
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5
fs/nfsd/nfsproc.c
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@ -567,12 +567,11 @@ static void nfsd_init_dirlist_pages(struct svc_rqst *rqstp,
struct xdr_buf *buf = &resp->dirlist;
struct xdr_stream *xdr = &resp->xdr;
count = clamp(count, (u32)(XDR_UNIT * 2), 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), (u32)PAGE_SIZE);
buf->buflen -= XDR_UNIT * 2;
buf->pages = rqstp->rq_next_page;
rqstp->rq_next_page++;