Re: [syzbot] Re: [syzbot] [squashfs?] KMSAN: uninit-value in pick_link

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Subject: Re: [syzbot] [squashfs?] KMSAN: uninit-value in pick_link
Author: lizhi.xu@windriver.com

why folio not inited?

#syz test: upstream 2f8c4f506285

diff --git a/mm/filemap.c b/mm/filemap.c
index 657bcd887fdb..b76a13395299 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3754,11 +3754,15 @@ static struct folio *do_read_cache_folio(struct address_space *mapping,
 		if (!folio)
 			return ERR_PTR(-ENOMEM);
 		err = filemap_add_folio(mapping, folio, index, gfp);
+		printk("err: %d, folio: %p, in: %p, %s\n", err, folio, mapping->host, __func__);
 		if (unlikely(err)) {
 			folio_put(folio);
 			if (err == -EEXIST)
 				goto repeat;
 			/* Presumably ENOMEM for xarray node */
+			void *kaddr = kmap_local_folio(folio, 0);
+			memset(kaddr, 0, folio_size(folio));
+			kunmap_local(kaddr);
 			return ERR_PTR(err);
 		}
 
@@ -3791,6 +3795,7 @@ static struct folio *do_read_cache_folio(struct address_space *mapping,
 		folio_put(folio);
 		if (err == AOP_TRUNCATED_PAGE)
 			goto repeat;
+		printk("err: %d, folio: %p, %s\n", err, folio, __func__);
 		return ERR_PTR(err);
 	}
 
diff --git a/fs/namei.c b/fs/namei.c
index 3a4c40e12f78..3f72aa8d604d 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -5272,6 +5272,8 @@ const char *page_get_link(struct dentry *dentry, struct inode *inode,
 		page = read_mapping_page(mapping, 0, NULL);
 		if (IS_ERR(page))
 			return (char*)page;
+		else if (IS_ERR(page_folio(page)))
+			return (char*)page_folio(page);
 	}
 	set_delayed_call(callback, page_put_link, page);
 	BUG_ON(mapping_gfp_mask(mapping) & __GFP_HIGHMEM);