From 0f5162480bd25bd97b91c9153db7afbd89698804 Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Fri, 17 Mar 2023 17:09:20 -0400 Subject: [PATCH] NFSD: Watch for rq_pages bounds checking errors in nfsd_splice_actor() There have been several bugs over the years where the NFSD splice actor has attempted to write outside the rq_pages array. This is a "should never happen" condition, but if for some reason the pipe splice actor should attempt to walk past the end of rq_pages, it needs to terminate the READ operation to prevent corruption of the pointer addresses in the fields just beyond the array. A server crash is thus prevented. Since the code is not behaving, the READ operation returns -EIO to the client. None of the READ payload data can be trusted if the splice actor isn't operating as expected. Suggested-by: Jeff Layton Signed-off-by: Chuck Lever Reviewed-by: Jeff Layton --- fs/nfsd/vfs.c | 6 +++++- include/linux/sunrpc/svc.h | 2 +- include/trace/events/sunrpc.h | 25 +++++++++++++++++++++++++ net/sunrpc/svc.c | 15 ++++++++++++++- 4 files changed, 45 insertions(+), 3 deletions(-) diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c index 5783209f17fc..10aa68ca82ef 100644 --- a/fs/nfsd/vfs.c +++ b/fs/nfsd/vfs.c @@ -930,6 +930,9 @@ nfsd_open_verified(struct svc_rqst *rqstp, struct svc_fh *fhp, int may_flags, * Grab and keep cached pages associated with a file in the svc_rqst * so that they can be passed to the network sendmsg/sendpage routines * directly. They will be released after the sending has completed. + * + * Return values: Number of bytes consumed, or -EIO if there are no + * remaining pages in rqstp->rq_pages. */ static int nfsd_splice_actor(struct pipe_inode_info *pipe, struct pipe_buffer *buf, @@ -948,7 +951,8 @@ nfsd_splice_actor(struct pipe_inode_info *pipe, struct pipe_buffer *buf, */ if (page == *(rqstp->rq_next_page - 1)) continue; - svc_rqst_replace_page(rqstp, page); + if (unlikely(!svc_rqst_replace_page(rqstp, page))) + return -EIO; } if (rqstp->rq_res.page_len == 0) // first call rqstp->rq_res.page_base = offset % PAGE_SIZE; diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h index 877891536c2f..f5af055280ff 100644 --- a/include/linux/sunrpc/svc.h +++ b/include/linux/sunrpc/svc.h @@ -422,7 +422,7 @@ struct svc_serv *svc_create(struct svc_program *, unsigned int, int (*threadfn)(void *data)); struct svc_rqst *svc_rqst_alloc(struct svc_serv *serv, struct svc_pool *pool, int node); -void svc_rqst_replace_page(struct svc_rqst *rqstp, +bool svc_rqst_replace_page(struct svc_rqst *rqstp, struct page *page); void svc_rqst_free(struct svc_rqst *); void svc_exit_thread(struct svc_rqst *); diff --git a/include/trace/events/sunrpc.h b/include/trace/events/sunrpc.h index 3ca54536f8f7..5a3bb42e1f50 100644 --- a/include/trace/events/sunrpc.h +++ b/include/trace/events/sunrpc.h @@ -1790,6 +1790,31 @@ DEFINE_EVENT(svc_rqst_status, svc_send, TP_PROTO(const struct svc_rqst *rqst, int status), TP_ARGS(rqst, status)); +TRACE_EVENT(svc_replace_page_err, + TP_PROTO(const struct svc_rqst *rqst), + + TP_ARGS(rqst), + TP_STRUCT__entry( + SVC_RQST_ENDPOINT_FIELDS(rqst) + + __field(const void *, begin) + __field(const void *, respages) + __field(const void *, nextpage) + ), + + TP_fast_assign( + SVC_RQST_ENDPOINT_ASSIGNMENTS(rqst); + + __entry->begin = rqst->rq_pages; + __entry->respages = rqst->rq_respages; + __entry->nextpage = rqst->rq_next_page; + ), + + TP_printk(SVC_RQST_ENDPOINT_FORMAT " begin=%p respages=%p nextpage=%p", + SVC_RQST_ENDPOINT_VARARGS, + __entry->begin, __entry->respages, __entry->nextpage) +); + TRACE_EVENT(svc_stats_latency, TP_PROTO( const struct svc_rqst *rqst diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c index fea7ce8fba14..633aa1eb476b 100644 --- a/net/sunrpc/svc.c +++ b/net/sunrpc/svc.c @@ -842,9 +842,21 @@ EXPORT_SYMBOL_GPL(svc_set_num_threads); * * When replacing a page in rq_pages, batch the release of the * replaced pages to avoid hammering the page allocator. + * + * Return values: + * %true: page replaced + * %false: array bounds checking failed */ -void svc_rqst_replace_page(struct svc_rqst *rqstp, struct page *page) +bool svc_rqst_replace_page(struct svc_rqst *rqstp, struct page *page) { + struct page **begin = rqstp->rq_pages; + struct page **end = &rqstp->rq_pages[RPCSVC_MAXPAGES]; + + if (unlikely(rqstp->rq_next_page < begin || rqstp->rq_next_page > end)) { + trace_svc_replace_page_err(rqstp); + return false; + } + if (*rqstp->rq_next_page) { if (!pagevec_space(&rqstp->rq_pvec)) __pagevec_release(&rqstp->rq_pvec); @@ -853,6 +865,7 @@ void svc_rqst_replace_page(struct svc_rqst *rqstp, struct page *page) get_page(page); *(rqstp->rq_next_page++) = page; + return true; } EXPORT_SYMBOL_GPL(svc_rqst_replace_page);