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

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: