From: Chuck Lever Date: Tue, 19 May 2026 13:34:22 +0000 (-0400) Subject: SUNRPC: Return an error from xdr_buf_to_bvec() on overflow X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=18c1cc69886192e33536498289d26dba6894e3d5;p=thirdparty%2Fkernel%2Flinux.git SUNRPC: Return an error from xdr_buf_to_bvec() on overflow xdr_buf_to_bvec() returns a slot count even when the caller's bvec budget is exhausted partway through the xdr_buf. Callers feed that count into iov_iter_bvec() and continue as if the conversion had succeeded, silently sending or writing fewer bytes than the data length declares. For an NFS WRITE the server reports the truncated transfer to the client as full success. The overflow represents an internal invariant violation: a higher layer reserved a bvec budget too small for the xdr_buf it then asked the encoder to convert. That is a server-side fault, not a media I/O failure and not a malformed client argument. Change xdr_buf_to_bvec() to return a signed int and have the overflow label return -ESERVERFAULT. Update the three callers to detect the negative return and fail the request: nfsd_vfs_write() folds the error into host_err, which nfserrno() translates to nfserr_serverfault for the WRITE reply; svc_udp_sendto() and svc_tcp_sendmsg() propagate the error out of the send path. Reported-by: Chris Mason Fixes: 2eb2b9358181 ("SUNRPC: Convert svc_tcp_sendmsg to use bio_vecs directly") Cc: stable@vger.kernel.org Reviewed-by: Jeff Layton Signed-off-by: Chuck Lever --- diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c index ba97e287c0072..cba4739694293 100644 --- a/fs/nfsd/vfs.c +++ b/fs/nfsd/vfs.c @@ -1440,7 +1440,7 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, unsigned long exp_op_flags = 0; unsigned int pflags = current->flags; bool restore_flags = false; - unsigned int nvecs; + int nvecs; trace_nfsd_write_opened(rqstp, fhp, offset, *cnt); @@ -1480,6 +1480,10 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, } nvecs = xdr_buf_to_bvec(rqstp->rq_bvec, rqstp->rq_maxpages, payload); + if (nvecs < 0) { + host_err = nvecs; + goto out_nfserr; + } since = READ_ONCE(file->f_wb_err); if (verf) diff --git a/include/linux/sunrpc/xdr.h b/include/linux/sunrpc/xdr.h index 31971b01d962a..b102b4f21e6b7 100644 --- a/include/linux/sunrpc/xdr.h +++ b/include/linux/sunrpc/xdr.h @@ -138,8 +138,8 @@ void xdr_terminate_string(const struct xdr_buf *, const u32); size_t xdr_buf_pagecount(const struct xdr_buf *buf); int xdr_alloc_bvec(struct xdr_buf *buf, gfp_t gfp); void xdr_free_bvec(struct xdr_buf *buf); -unsigned int xdr_buf_to_bvec(struct bio_vec *bvec, unsigned int bvec_size, - const struct xdr_buf *xdr); +int xdr_buf_to_bvec(struct bio_vec *bvec, unsigned int bvec_size, + const struct xdr_buf *xdr); int xdr_buf_to_sg(const struct xdr_buf *buf, unsigned int offset, unsigned int len, struct scatterlist *sg, unsigned int nsg); int xdr_buf_to_sg_alloc(const struct xdr_buf *buf, unsigned int offset, diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c index 7be3de1a1aed9..c434b6a6637d9 100644 --- a/net/sunrpc/svcsock.c +++ b/net/sunrpc/svcsock.c @@ -732,7 +732,7 @@ static int svc_udp_sendto(struct svc_rqst *rqstp) .msg_flags = MSG_SPLICE_PAGES, .msg_controllen = sizeof(buffer), }; - unsigned int count; + int count; int err; svc_udp_release_ctxt(xprt, rqstp->rq_xprt_ctxt); @@ -746,6 +746,10 @@ static int svc_udp_sendto(struct svc_rqst *rqstp) goto out_notconn; count = xdr_buf_to_bvec(svsk->sk_bvec, SUNRPC_MAX_UDP_SENDPAGES, xdr); + if (count < 0) { + err = count; + goto out_trace; + } iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, svsk->sk_bvec, count, rqstp->rq_res.len); @@ -757,6 +761,7 @@ static int svc_udp_sendto(struct svc_rqst *rqstp) err = sock_sendmsg(svsk->sk_sock, &msg); } +out_trace: trace_svcsock_udp_send(xprt, err); mutex_unlock(&xprt->xpt_mutex); @@ -1237,7 +1242,7 @@ static int svc_tcp_sendmsg(struct svc_sock *svsk, struct svc_rqst *rqstp, struct msghdr msg = { .msg_flags = MSG_SPLICE_PAGES, }; - unsigned int count; + int count; void *buf; int ret; @@ -1253,10 +1258,15 @@ static int svc_tcp_sendmsg(struct svc_sock *svsk, struct svc_rqst *rqstp, count = xdr_buf_to_bvec(svsk->sk_bvec + 1, rqstp->rq_maxpages, &rqstp->rq_res); + if (count < 0) { + ret = count; + goto out; + } iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, svsk->sk_bvec, 1 + count, sizeof(marker) + rqstp->rq_res.len); ret = sock_sendmsg(svsk->sk_sock, &msg); +out: page_frag_free(buf); return ret; } diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c index 8f52782d8a372..fa6a30b5f0463 100644 --- a/net/sunrpc/xdr.c +++ b/net/sunrpc/xdr.c @@ -139,13 +139,14 @@ xdr_free_bvec(struct xdr_buf *buf) /** * xdr_buf_to_bvec - Copy components of an xdr_buf into a bio_vec array * @bvec: bio_vec array to populate - * @bvec_size: element count of @bio_vec + * @bvec_size: element count of @bvec * @xdr: xdr_buf to be copied * - * Returns the number of entries consumed in @bvec. + * Returns the number of entries consumed in @bvec on success, or + * -ESERVERFAULT when @xdr does not fit within @bvec_size entries. */ -unsigned int xdr_buf_to_bvec(struct bio_vec *bvec, unsigned int bvec_size, - const struct xdr_buf *xdr) +int xdr_buf_to_bvec(struct bio_vec *bvec, unsigned int bvec_size, + const struct xdr_buf *xdr) { const struct kvec *head = xdr->head; const struct kvec *tail = xdr->tail; @@ -187,7 +188,7 @@ unsigned int xdr_buf_to_bvec(struct bio_vec *bvec, unsigned int bvec_size, bvec_overflow: pr_warn_once("%s: bio_vec array overflow\n", __func__); - return count; + return -ESERVERFAULT; } EXPORT_SYMBOL_GPL(xdr_buf_to_bvec);