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SUNRPC: Fix the calculation of xdr->end in xdr_get_next_encode_buffer()

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I found that NFSD's new NFSv3 READDIRPLUS XDR encoder was screwing up
right at the end of the page array. xdr_get_next_encode_buffer() does
not compute the value of xdr->end correctly:

 * The check to see if we're on the final available page in xdr->buf
   needs to account for the space consumed by @nbytes.

 * The new xdr->end value needs to account for the portion of @nbytes
   that is to be encoded into the previous buffer.

Fixes: 2825a7f907 ("nfsd4: allow encoding across page boundaries")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: NeilBrown <neilb@suse.de>
Reviewed-by: J. Bruce Fields <bfields@fieldses.org>
This commit is contained in:
Chuck Lever 2022-06-07 16:47:52 -04:00
parent f012e95b37
commit 6c254bf3b6
1 changed files with 5 additions and 1 deletions
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6
net/sunrpc/xdr.c
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@ -979,7 +979,11 @@ static __be32 *xdr_get_next_encode_buffer(struct xdr_stream *xdr,
*/
xdr->p = (void *)p + frag2bytes;
space_left = xdr->buf->buflen - xdr->buf->len;
xdr->end = (void *)p + min_t(int, space_left, PAGE_SIZE);
if (space_left - nbytes >= PAGE_SIZE)
xdr->end = (void *)p + PAGE_SIZE;
else
xdr->end = (void *)p + space_left - frag1bytes;
xdr->buf->page_len += frag2bytes;
xdr->buf->len += nbytes;
return p;