From 61182c796d74f54ba66d17bac6f516183ec09af2 Mon Sep 17 00:00:00 2001 From: Anna Schumaker Date: Fri, 23 Jun 2023 11:43:14 -0400 Subject: SUNRPC: kmap() the xdr pages during decode If the pages are in HIGHMEM then we need to make sure they're mapped before trying to read data off of them, otherwise we could end up with a NULL pointer dereference. The downside to this is that we need an extra cleanup step at the end of decode to kunmap() the last page. I introduced an xdr_finish_decode() function to do this. Right now this function only calls the unmap_current_page() function, but other generic cleanup steps could be added in the future if we come across anything else. Reported-by: Krzysztof Kozlowski Signed-off-by: Anna Schumaker --- net/sunrpc/xdr.c | 27 ++++++++++++++++++++++++++- 1 file changed, 26 insertions(+), 1 deletion(-) (limited to 'net/sunrpc/xdr.c') diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c index 2a22e78af116..f5011344dfe7 100644 --- a/net/sunrpc/xdr.c +++ b/net/sunrpc/xdr.c @@ -1288,6 +1288,14 @@ static unsigned int xdr_set_tail_base(struct xdr_stream *xdr, return xdr_set_iov(xdr, buf->tail, base, len); } +static void xdr_stream_unmap_current_page(struct xdr_stream *xdr) +{ + if (xdr->page_kaddr) { + kunmap_local(xdr->page_kaddr); + xdr->page_kaddr = NULL; + } +} + static unsigned int xdr_set_page_base(struct xdr_stream *xdr, unsigned int base, unsigned int len) { @@ -1305,12 +1313,18 @@ static unsigned int xdr_set_page_base(struct xdr_stream *xdr, if (len > maxlen) len = maxlen; + xdr_stream_unmap_current_page(xdr); xdr_stream_page_set_pos(xdr, base); base += xdr->buf->page_base; pgnr = base >> PAGE_SHIFT; xdr->page_ptr = &xdr->buf->pages[pgnr]; - kaddr = page_address(*xdr->page_ptr); + + if (PageHighMem(*xdr->page_ptr)) { + xdr->page_kaddr = kmap_local_page(*xdr->page_ptr); + kaddr = xdr->page_kaddr; + } else + kaddr = page_address(*xdr->page_ptr); pgoff = base & ~PAGE_MASK; xdr->p = (__be32*)(kaddr + pgoff); @@ -1364,6 +1378,7 @@ void xdr_init_decode(struct xdr_stream *xdr, struct xdr_buf *buf, __be32 *p, struct rpc_rqst *rqst) { xdr->buf = buf; + xdr->page_kaddr = NULL; xdr_reset_scratch_buffer(xdr); xdr->nwords = XDR_QUADLEN(buf->len); if (xdr_set_iov(xdr, buf->head, 0, buf->len) == 0 && @@ -1396,6 +1411,16 @@ void xdr_init_decode_pages(struct xdr_stream *xdr, struct xdr_buf *buf, } EXPORT_SYMBOL_GPL(xdr_init_decode_pages); +/** + * xdr_finish_decode - Clean up the xdr_stream after decoding data. + * @xdr: pointer to xdr_stream struct + */ +void xdr_finish_decode(struct xdr_stream *xdr) +{ + xdr_stream_unmap_current_page(xdr); +} +EXPORT_SYMBOL(xdr_finish_decode); + static __be32 * __xdr_inline_decode(struct xdr_stream *xdr, size_t nbytes) { unsigned int nwords = XDR_QUADLEN(nbytes); -- cgit v1.2.3