From e77340e00300df9b6591d686f186eea60c67206f Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Fri, 23 Jun 2017 17:17:44 -0400 Subject: [PATCH] svcrdma: Improve Read chunk sanity checking Identify malformed transport headers and unsupported chunk combinations as early as possible. - Reject RPC-over-RDMA messages that contain more than one Read chunk, since this implementation currently does not support more than one per RPC transaction. - Ensure that segment lengths are not crazy. - Remove the segment count check. With a 1KB inline threshold, the largest number of Read segments that can be conveyed is about 40 (for a RDMA_NOMSG Call message). This is nowhere near RPCSVC_MAXPAGES. As far as I can tell, that was just a sanity check and does not enforce an implementation limit. Signed-off-by: Chuck Lever Signed-off-by: J. Bruce Fields --- net/sunrpc/xprtrdma/svc_rdma_recvfrom.c | 55 +++++++++++++++++-------- 1 file changed, 37 insertions(+), 18 deletions(-) diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c index 55ad335bbef1..885ad9503ee0 100644 --- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c +++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c @@ -117,15 +117,47 @@ static void rdma_build_arg_xdr(struct svc_rqst *rqstp, rqstp->rq_arg.tail[0].iov_len = 0; } -static __be32 *xdr_check_read_list(__be32 *p, __be32 *end) +/* This accommodates the largest possible Position-Zero + * Read chunk or Reply chunk, in one segment. + */ +#define MAX_BYTES_SPECIAL_SEG ((u32)((RPCSVC_MAXPAGES + 2) << PAGE_SHIFT)) + +/* Sanity check the Read list. + * + * Implementation limits: + * - This implementation supports only one Read chunk. + * + * Sanity checks: + * - Read list does not overflow buffer. + * - Segment size limited by largest NFS data payload. + * + * The segment count is limited to how many segments can + * fit in the transport header without overflowing the + * buffer. That's about 40 Read segments for a 1KB inline + * threshold. + * + * Returns pointer to the following Write list. + */ +static __be32 *xdr_check_read_list(__be32 *p, const __be32 *end) { - __be32 *next; + u32 position; + bool first; + first = true; while (*p++ != xdr_zero) { - next = p + rpcrdma_readchunk_maxsz - 1; - if (next > end) + if (first) { + position = be32_to_cpup(p++); + first = false; + } else if (be32_to_cpup(p++) != position) { + return NULL; + } + p++; /* handle */ + if (be32_to_cpup(p++) > MAX_BYTES_SPECIAL_SEG) + return NULL; + p += 2; /* offset */ + + if (p > end) return NULL; - p = next; } return p; } @@ -478,16 +510,6 @@ int rdma_read_chunk_frmr(struct svcxprt_rdma *xprt, return ret; } -static unsigned int -rdma_rcl_chunk_count(struct rpcrdma_read_chunk *ch) -{ - unsigned int count; - - for (count = 0; ch->rc_discrim != xdr_zero; ch++) - count++; - return count; -} - /* If there was additional inline content, append it to the end of arg.pages. * Tail copy has to be done after the reader function has determined how many * pages are needed for RDMA READ. @@ -567,9 +589,6 @@ static int rdma_read_chunks(struct svcxprt_rdma *xprt, if (!ch) return 0; - if (rdma_rcl_chunk_count(ch) > RPCSVC_MAXPAGES) - return -EINVAL; - /* The request is completed when the RDMA_READs complete. The * head context keeps all the pages that comprise the * request. -- 2.20.1