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nfsd4: Handle the NFSv4 READDIR 'dircount' hint being zero

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RFC3530 notes that the 'dircount' field may be zero, in which case the
recommendation is to ignore it, and only enforce the 'maxcount' field.
In RFC5661, this recommendation to ignore a zero valued field becomes a
requirement.

Fixes: aee3776441 ("nfsd4: fix rd_dircount enforcement")
Cc: <stable@vger.kernel.org>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This commit is contained in:
Trond Myklebust 2021-09-30 15:44:41 -04:00 committed by Chuck Lever
parent 1d625050c7
commit f2e717d655
1 changed files with 11 additions and 8 deletions
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19
fs/nfsd/nfs4xdr.c
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@ -3544,15 +3544,18 @@ nfsd4_encode_dirent(void *ccdv, const char *name, int namlen,
goto fail;
cd->rd_maxcount -= entry_bytes;
/*
* RFC 3530 14.2.24 describes rd_dircount as only a "hint", so
* let's always let through the first entry, at least:
* RFC 3530 14.2.24 describes rd_dircount as only a "hint", and
* notes that it could be zero. If it is zero, then the server
* should enforce only the rd_maxcount value.
*/
if (!cd->rd_dircount)
goto fail;
name_and_cookie = 4 + 4 * XDR_QUADLEN(namlen) + 8;
if (name_and_cookie > cd->rd_dircount && cd->cookie_offset)
goto fail;
cd->rd_dircount -= min(cd->rd_dircount, name_and_cookie);
if (cd->rd_dircount) {
name_and_cookie = 4 + 4 * XDR_QUADLEN(namlen) + 8;
if (name_and_cookie > cd->rd_dircount && cd->cookie_offset)
goto fail;
cd->rd_dircount -= min(cd->rd_dircount, name_and_cookie);
if (!cd->rd_dircount)
cd->rd_maxcount = 0;
}
cd->cookie_offset = cookie_offset;
skip_entry: