[PATCH 5.10 678/770] NFSD: Fix reads with a non-zero offset that dont end on a page boundary

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5.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Chuck Lever <chuck.lever@xxxxxxxxxx>

[ Upstream commit ac8db824ead0de2e9111337c401409d010fba2f0 ]

This was found when virtual machines with nfs-mounted qcow2 disks
failed to boot properly.

Reported-by: Anders Blomdell <anders.blomdell@xxxxxxxxxxxxxx>
Suggested-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Link: https://bugzilla.redhat.com/show_bug.cgi?id=2142132
Fixes: bfbfb6182ad1 ("nfsd_splice_actor(): handle compound pages")
[ cel: "‘for’ loop initial declarations are only allowed in C99 or C11 mode" ]
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 fs/nfsd/vfs.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index e29034b1e6128..4ff626c912cc3 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -888,11 +888,11 @@ nfsd_splice_actor(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
 	struct svc_rqst *rqstp = sd->u.data;
 	struct page *page = buf->page;	// may be a compound one
 	unsigned offset = buf->offset;
-	int i;
+	struct page *last_page;
 
-	page += offset / PAGE_SIZE;
-	for (i = sd->len; i > 0; i -= PAGE_SIZE)
-		svc_rqst_replace_page(rqstp, page++);
+	last_page = page + (offset + sd->len - 1) / PAGE_SIZE;
+	for (page += offset / PAGE_SIZE; page <= last_page; page++)
+		svc_rqst_replace_page(rqstp, page);
 	if (rqstp->rq_res.page_len == 0)	// first call
 		rqstp->rq_res.page_base = offset % PAGE_SIZE;
 	rqstp->rq_res.page_len += sd->len;
-- 
2.43.0







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