From e864c189e1d63f2f6a052e296f0da0616d88b625 Mon Sep 17 00:00:00 2001 From: "J. Bruce Fields" Date: Fri, 10 Jun 2016 16:56:05 -0400 Subject: [PATCH] nfsd: catch errors in decode_fattr earlier 3c8e03166ae2 "NFSv4: do exact check about attribute specified" fixed some handling of unsupported-attribute errors, but it also delayed checking for unwriteable attributes till after we decode them. This could lead to odd behavior in the case a client attemps to set an attribute we don't know about followed by one we try to parse. In that case the parser for the known attribute will attempt to parse the unknown attribute. It should fail in some safe way, but the error might at least be incorrect (probably bad_xdr instead of inval). So, it's better to do that check at the start. As far as I know this doesn't cause any problems with current clients but it might be a minor issue e.g. if we encounter a future client that supports a new attribute that we currently don't. Cc: Yu Zhiguo Signed-off-by: J. Bruce Fields --- fs/nfsd/nfs4xdr.c | 15 +++++++++------ fs/nfsd/nfsd.h | 6 +++++- 2 files changed, 14 insertions(+), 7 deletions(-) diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c index a99bbb88c6e1..281739e1d477 100644 --- a/fs/nfsd/nfs4xdr.c +++ b/fs/nfsd/nfs4xdr.c @@ -310,6 +310,14 @@ nfsd4_decode_fattr(struct nfsd4_compoundargs *argp, u32 *bmval, if ((status = nfsd4_decode_bitmap(argp, bmval))) return status; + if (bmval[0] & ~NFSD_WRITEABLE_ATTRS_WORD0 + || bmval[1] & ~NFSD_WRITEABLE_ATTRS_WORD1 + || bmval[2] & ~NFSD_WRITEABLE_ATTRS_WORD2) { + if (nfsd_attrs_supported(argp->minorversion, bmval)) + return nfserr_inval; + return nfserr_attrnotsupp; + } + READ_BUF(4); expected_len = be32_to_cpup(p++); @@ -449,12 +457,7 @@ nfsd4_decode_fattr(struct nfsd4_compoundargs *argp, u32 *bmval, return nfserr_jukebox; } #endif - - if (bmval[0] & ~NFSD_WRITEABLE_ATTRS_WORD0 - || bmval[1] & ~NFSD_WRITEABLE_ATTRS_WORD1 - || bmval[2] & ~NFSD_WRITEABLE_ATTRS_WORD2) - READ_BUF(expected_len - len); - else if (len != expected_len) + if (len != expected_len) goto xdr_error; DECODE_TAIL; diff --git a/fs/nfsd/nfsd.h b/fs/nfsd/nfsd.h index a72d4163273a..7155239b2908 100644 --- a/fs/nfsd/nfsd.h +++ b/fs/nfsd/nfsd.h @@ -379,7 +379,11 @@ static inline bool nfsd_attrs_supported(u32 minorversion, u32 *bmval) #define NFSD_WRITEONLY_ATTRS_WORD1 \ (FATTR4_WORD1_TIME_ACCESS_SET | FATTR4_WORD1_TIME_MODIFY_SET) -/* These are the only attrs allowed in CREATE/OPEN/SETATTR. */ +/* + * These are the only attrs allowed in CREATE/OPEN/SETATTR. Don't add + * a writeable attribute here without also adding code to parse it to + * nfsd4_decode_fattr(). + */ #define NFSD_WRITEABLE_ATTRS_WORD0 \ (FATTR4_WORD0_SIZE | FATTR4_WORD0_ACL) #define NFSD_WRITEABLE_ATTRS_WORD1 \ -- 2.20.1