Commit 1199db60 authored Nov 02, 2017 by David Howells

afs: Fix total-length calculation for multiple-page send

Fix the total-length calculation in afs_make_call() when the operation
being dispatched has data from a series of pages attached.

Despite the patched code looking like that it should reduce mathematically
to the current code, it doesn't because the 32-bit unsigned arithmetic
being used to calculate the page-offset-difference doesn't correctly extend
to a 64-bit value when the result is effectively negative.

Without this, some FS.StoreData operations that span multiple pages fail,
reporting too little or too much data.

Signed-off-by: David Howells <dhowells@redhat.com>

parent 5f0fc8ba

fs/afs/rxrpc.c

+11 −2

Original line number	Diff line number	Diff line
		@@ -350,8 +350,17 @@ long afs_make_call(struct afs_addr_cursor ac, struct afs_call call,
		*/
		tx_total_len = call->request_size;
		if (call->send_pages) {
		if (call->last == call->first) {
		tx_total_len += call->last_to - call->first_offset;
		tx_total_len += (call->last - call->first) * PAGE_SIZE;
		} else {
		/* It looks mathematically like you should be able to
		* combine the following lines with the ones above, but
		* unsigned arithmetic is fun when it wraps...
		*/
		tx_total_len += PAGE_SIZE - call->first_offset;
		tx_total_len += call->last_to;
		tx_total_len += (call->last - call->first - 1) * PAGE_SIZE;
		}
		}

		/* create a call */

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