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

[syzbot <syzbot+24ac24ff58dc5b0d26b9@syzkaller.appspotmail.com>]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org.

***

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

if alloc new folio for filemap, init mem to zero

#syz test: upstream 2f8c4f506285

diff --git a/mm/filemap.c b/mm/filemap.c
index 657bcd887fdb..8faa75f6923c 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);
 		}