util: fix confusion between offset in the iovec array and in the entry2024_03_20.71dd405

In write_remainder() 'skip' is the offset to start the operation from
in the iovec array.

In iov_skip_bytes(), 'skip' is also the offset in the iovec array but
'offset' is the first unskipped byte in the iovec entry.

As write_remainder() uses 'skip' for both, 'skip' is reset to the
first unskipped byte in the iovec entry rather to staying the first
unskipped byte in the iovec array.

Fix the problem by introducing a new variable not to overwrite 'skip'
on each loop.

Fixes: 8bdb0883b441 ("util: Add write_remainder() helper")
Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 5 insertions, 4 deletions

diff --git a/util.c b/util.c
index 3b2393d..849fa7f 100644
--- a/util.c
+++ b/util.c
@@ -533,13 +533,14 @@ int do_clone(int (*fn)(void *), char *stack_area, size_t stack_size, int flags,
 int write_remainder(int fd, const struct iovec *iov, int iovcnt, size_t skip)
 {
 	int i;
+	size_t offset;
 
-	while ((i = iov_skip_bytes(iov, iovcnt, skip, &skip)) < iovcnt) {
+	while ((i = iov_skip_bytes(iov, iovcnt, skip, &offset)) < iovcnt) {
 		ssize_t rc;
 
-		if (skip) {
-			rc = write(fd, (char *)iov[i].iov_base + skip,
-				   iov[i].iov_len - skip);
+		if (offset) {
+			rc = write(fd, (char *)iov[i].iov_base + offset,
+				   iov[i].iov_len - offset);
 		} else {
 			rc = writev(fd, &iov[i], iovcnt - i);
 		}