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..a830b22c9708 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3754,6 +3754,7 @@ 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, read_folio: %p %s\n", err, folio, mapping->host, filler, __func__);
 		if (unlikely(err)) {
 			folio_put(folio);
 			if (err == -EEXIST)
@@ -3787,6 +3788,7 @@ static struct folio *do_read_cache_folio(struct address_space *mapping,
 
 filler:
 	err = filemap_read_folio(file, filler, folio);
+	printk("err: %d, folio: %p, folio uptod: %d, %s\n", err, folio, folio_test_uptodate(folio),  __func__);
 	if (err) {
 		folio_put(folio);
 		if (err == AOP_TRUNCATED_PAGE)
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);
diff --git a/fs/squashfs/file.c b/fs/squashfs/file.c
index a8c1e7f9a609..d581cea14316 100644
--- a/fs/squashfs/file.c
+++ b/fs/squashfs/file.c
@@ -459,6 +459,8 @@ static int squashfs_read_folio(struct file *file, struct folio *folio)
 	TRACE("Entered squashfs_readpage, page index %lx, start block %llx\n",
 				page->index, squashfs_i(inode)->start);
 
+	printk("folio: %p, isize: %d, pidx: %d, idx: %d, fe: %d, %s\n", 
+		folio, i_size_read(inode), page->index, index, file_end, __func__);
 	if (page->index >= ((i_size_read(inode) + PAGE_SIZE - 1) >>
 					PAGE_SHIFT))
 		goto out;
@@ -478,6 +480,7 @@ static int squashfs_read_folio(struct file *file, struct folio *folio)
 	} else
 		res = squashfs_readpage_fragment(page, expected);
 
+	printk("res: %d, %s\n", res, __func__);
 	if (!res)
 		return 0;
 
@@ -489,6 +492,7 @@ static int squashfs_read_folio(struct file *file, struct folio *folio)
 	if (res == 0)
 		SetPageUptodate(page);
 	unlock_page(page);
+	printk("out, res: %d, %s\n", res, __func__);
 
 	return res;
 }
diff --git a/fs/squashfs/symlink.c b/fs/squashfs/symlink.c
index 6ef735bd841a..7e41196ea8de 100644
--- a/fs/squashfs/symlink.c
+++ b/fs/squashfs/symlink.c
@@ -49,6 +49,8 @@ static int squashfs_symlink_read_folio(struct file *file, struct folio *folio)
 	/*
 	 * Skip index bytes into symlink metadata.
 	 */
+	printk("folio: %p, isize: %d, idx: %d, %s\n", 
+		folio, i_size_read(inode), index, __func__);
 	if (index) {
 		bytes = squashfs_read_metadata(sb, NULL, &block, &offset,
 								index);
@@ -93,6 +95,7 @@ static int squashfs_symlink_read_folio(struct file *file, struct folio *folio)
 	flush_dcache_folio(folio);
 	error = 0;
 out:
+	printk("error: %d, %s\n", error, __func__);
 	folio_end_read(folio, error == 0);
 	return error;
 }