linux-kernel - Re: [syzbot] [PATCH v2] netfs: Fix a KMSAN uninit-value error in netfs_clear

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Message-ID: <66fb8cbd.050a0220.6bad9.004e.GAE@google.com>
Date: Mon, 30 Sep 2024 22:46:37 -0700
From: syzbot <syzbot+921873345a95f4dae7e9@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org
Subject: Re: [syzbot] [PATCH v2] netfs: Fix a KMSAN uninit-value error in netfs_clear_buffer

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***

Subject: [PATCH v2] netfs: Fix a KMSAN uninit-value error in netfs_clear_buffer
Author: marcus.yu.56@...il.com

#syz test

Use folioq_count instead of folioq_nr_slots to fix a KMSAN uninit-value
error in netfs_clear_buffer

Signed-off-by: Chang Yu <marcus.yu.56@...il.com>
Reported-by: syzbot+921873345a95f4dae7e9@...kaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=921873345a95f4dae7e9
Fixes: cd0277ed0c18 ("netfs: Use new folio_queue data type and iterator instead of xarray iter")
---
Changes since v2:
  - Use folioq_count when putting pointers. This avoids touching
    uninitialized pointer and is a deeper fix than just using
    kzalloc.


 fs/netfs/misc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/netfs/misc.c b/fs/netfs/misc.c
index 63280791de3b..78fe5796b2b2 100644
--- a/fs/netfs/misc.c
+++ b/fs/netfs/misc.c
@@ -102,7 +102,7 @@ void netfs_clear_buffer(struct netfs_io_request *rreq)
 
 	while ((p = rreq->buffer)) {
 		rreq->buffer = p->next;
-		for (int slot = 0; slot < folioq_nr_slots(p); slot++) {
+		for (int slot = 0; slot < folioq_count(p); slot++) {
 			struct folio *folio = folioq_folio(p, slot);
 			if (!folio)
 				continue;
-- 
2.46.2