linux-kernel - Re: KCSAN: data-race in generic_fillattr / shmem

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Message-Id: <20240908062701.7906-1-aha310510@gmail.com>
Date: Sun,  8 Sep 2024 15:27:01 +0900
From: Jeongjun Park <aha310510@...il.com>
To: syzbot+702361cf7e3d95758761@...kaller.appspotmail.com
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: KCSAN: data-race in generic_fillattr / shmem_mknod (2)

#syz test git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

---
 fs/ext4/super.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index e72145c4ae5a..8cc5e19bfe78 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -346,7 +346,7 @@ __u32 ext4_free_group_clusters(struct super_block *sb,
 __u32 ext4_free_inodes_count(struct super_block *sb,
 			      struct ext4_group_desc *bg)
 {
-	return le16_to_cpu(bg->bg_free_inodes_count_lo) |
+	return le16_to_cpu(READ_ONCE(bg->bg_free_inodes_count_lo)) |
 		(EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT ?
 		 (__u32)le16_to_cpu(bg->bg_free_inodes_count_hi) << 16 : 0);
 }
@@ -402,7 +402,7 @@ void ext4_free_group_clusters_set(struct super_block *sb,
 void ext4_free_inodes_set(struct super_block *sb,
 			  struct ext4_group_desc *bg, __u32 count)
 {
-	bg->bg_free_inodes_count_lo = cpu_to_le16((__u16)count);
+	WRITE_ONCE(bg->bg_free_inodes_count_lo, cpu_to_le16((__u16)count));
 	if (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT)
 		bg->bg_free_inodes_count_hi = cpu_to_le16(count >> 16);
 }
--