From ace149e0830c380ddfce7e466fe860ca502fe4ee Mon Sep 17 00:00:00 2001
From: Trond Myklebust <trond.myklebust@hammerspace.com>
Date: Fri, 13 Sep 2024 13:57:04 -0400
Subject: [PATCH] filemap: Fix bounds checking in filemap_read()
If the caller supplies an iocb->ki_pos value that is close to the
filesystem upper limit, and an iterator with a count that causes us to
overflow that limit, then filemap_read() enters an infinite loop.
This behaviour was discovered when testing xfstests generic/525 with the
"localio" optimisation for loopback NFS mounts.
Reported-by: Mike Snitzer <snitzer@kernel.org>
Fixes: c2a9737f45e2 ("vfs,mm: fix a dead loop in truncate_inode_pages_range()")
Tested-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
mm/filemap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/filemap.c b/mm/filemap.c
index 36d22968be9a1..56fa431c52af7 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2625,7 +2625,7 @@ ssize_t filemap_read(struct kiocb *iocb, struct iov_iter *iter,
if (unlikely(!iov_iter_count(iter)))
return 0;
- iov_iter_truncate(iter, inode->i_sb->s_maxbytes);
+ iov_iter_truncate(iter, inode->i_sb->s_maxbytes - iocb->ki_pos);
folio_batch_init(&fbatch);
do {
--
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