[PATCH] fs: btrfs: fix out of bounds write

[Alex Shumsky <alexthreed@gmail.com>]

Fix btrfs_read/read_and_truncate_page write out of bounds of destination
buffer. Old behavior break bootstd malloc'd buffers of exact file size.
Previously this OOB write have not been noticed because distroboot usually
read files into huge static memory areas.

Signed-off-by: Alex Shumsky <alexthreed@gmail.com>
---

 fs/btrfs/inode.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 4691612eda..b51f578b49 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -640,7 +640,7 @@ static int read_and_truncate_page(struct btrfs_path *path,
 	extent_type = btrfs_file_extent_type(leaf, fi);
 	if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
 		ret = btrfs_read_extent_inline(path, fi, buf);
-		memcpy(dest, buf + page_off, min(page_len, ret));
+		memcpy(dest, buf + page_off, min(min(page_len, ret), len));
 		free(buf);
 		return len;
 	}
@@ -652,7 +652,7 @@ static int read_and_truncate_page(struct btrfs_path *path,
 		free(buf);
 		return ret;
 	}
-	memcpy(dest, buf + page_off, page_len);
+	memcpy(dest, buf + page_off, min(page_len, len));
 	free(buf);
 	return len;
 }
-- 
2.34.1