Merge tag 'nfsd-5.19-1' of git://git.kernel.org/pub/scm/linux/kernel/git/cel/linux

Pull nfsd fixes from Chuck Lever:
 "Notable changes:

   - There is now a backup maintainer for NFSD

  Notable fixes:

   - Prevent array overruns in svc_rdma_build_writes()

   - Prevent buffer overruns when encoding NFSv3 READDIR results

   - Fix a potential UAF in nfsd_file_put()"

* tag 'nfsd-5.19-1' of git://git.kernel.org/pub/scm/linux/kernel/git/cel/linux:
  SUNRPC: Remove pointer type casts from xdr_get_next_encode_buffer()
  SUNRPC: Clean up xdr_get_next_encode_buffer()
  SUNRPC: Clean up xdr_commit_encode()
  SUNRPC: Optimize xdr_reserve_space()
  SUNRPC: Fix the calculation of xdr->end in xdr_get_next_encode_buffer()
  SUNRPC: Trap RDMA segment overflows
  NFSD: Fix potential use-after-free in nfsd_file_put()
  MAINTAINERS: reciprocal co-maintainership for file locking and nfsd

2 files changed, 25 insertions, 16 deletions

diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index df194cc07035..f87a2d8f23a7 100644
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -919,7 +919,7 @@ void xdr_init_encode(struct xdr_stream *xdr, struct xdr_buf *buf, __be32 *p,
 EXPORT_SYMBOL_GPL(xdr_init_encode);
 
 /**
- * xdr_commit_encode - Ensure all data is written to buffer
+ * __xdr_commit_encode - Ensure all data is written to buffer
  * @xdr: pointer to xdr_stream
  *
  * We handle encoding across page boundaries by giving the caller a
@@ -931,26 +931,29 @@ EXPORT_SYMBOL_GPL(xdr_init_encode);
  * required at the end of encoding, or any other time when the xdr_buf
  * data might be read.
  */
-inline void xdr_commit_encode(struct xdr_stream *xdr)
+void __xdr_commit_encode(struct xdr_stream *xdr)
 {
-	int shift = xdr->scratch.iov_len;
+	size_t shift = xdr->scratch.iov_len;
 	void *page;
 
-	if (shift == 0)
-		return;
 	page = page_address(*xdr->page_ptr);
 	memcpy(xdr->scratch.iov_base, page, shift);
 	memmove(page, page + shift, (void *)xdr->p - page);
 	xdr_reset_scratch_buffer(xdr);
 }
-EXPORT_SYMBOL_GPL(xdr_commit_encode);
+EXPORT_SYMBOL_GPL(__xdr_commit_encode);
 
-static __be32 *xdr_get_next_encode_buffer(struct xdr_stream *xdr,
-		size_t nbytes)
+/*
+ * The buffer space to be reserved crosses the boundary between
+ * xdr->buf->head and xdr->buf->pages, or between two pages
+ * in xdr->buf->pages.
+ */
+static noinline __be32 *xdr_get_next_encode_buffer(struct xdr_stream *xdr,
+						   size_t nbytes)
 {
-	__be32 *p;
 	int space_left;
 	int frag1bytes, frag2bytes;
+	void *p;
 
 	if (nbytes > PAGE_SIZE)
 		goto out_overflow; /* Bigger buffers require special handling */
@@ -964,6 +967,7 @@ static __be32 *xdr_get_next_encode_buffer(struct xdr_stream *xdr,
 		xdr->buf->page_len += frag1bytes;
 	xdr->page_ptr++;
 	xdr->iov = NULL;
+
 	/*
 	 * If the last encode didn't end exactly on a page boundary, the
 	 * next one will straddle boundaries.  Encode into the next
@@ -972,14 +976,19 @@ static __be32 *xdr_get_next_encode_buffer(struct xdr_stream *xdr,
 	 * space at the end of the previous buffer:
 	 */
 	xdr_set_scratch_buffer(xdr, xdr->p, frag1bytes);
-	p = page_address(*xdr->page_ptr);
+
 	/*
-	 * Note this is where the next encode will start after we've
-	 * shifted this one back:
+	 * xdr->p is where the next encode will start after
+	 * xdr_commit_encode() has shifted this one back:
 	 */
-	xdr->p = (void *)p + frag2bytes;
+	p = page_address(*xdr->page_ptr);
+	xdr->p = p + frag2bytes;
 	space_left = xdr->buf->buflen - xdr->buf->len;
-	xdr->end = (void *)p + min_t(int, space_left, PAGE_SIZE);
+	if (space_left - nbytes >= PAGE_SIZE)
+		xdr->end = p + PAGE_SIZE;
+	else
+		xdr->end = p + space_left - frag1bytes;
+
 	xdr->buf->page_len += frag2bytes;
 	xdr->buf->len += nbytes;
 	return p;
diff --git a/net/sunrpc/xprtrdma/svc_rdma_rw.c b/net/sunrpc/xprtrdma/svc_rdma_rw.c
index 5f0155fdefc7..11cf7c646644 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_rw.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_rw.c
@@ -478,10 +478,10 @@ svc_rdma_build_writes(struct svc_rdma_write_info *info,
 		unsigned int write_len;
 		u64 offset;
 
-		seg = &info->wi_chunk->ch_segments[info->wi_seg_no];
-		if (!seg)
+		if (info->wi_seg_no >= info->wi_chunk->ch_segcount)
 			goto out_overflow;
 
+		seg = &info->wi_chunk->ch_segments[info->wi_seg_no];
 		write_len = min(remaining, seg->rs_length - info->wi_seg_off);
 		if (!write_len)
 			goto out_overflow;