Re: [syzbot] [mm?] KCSAN: data-race in generic_fillattr / shmem_mknod (2)

[Jeongjun Park <aha310510@gmail.com>]

#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..466aece8518f 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -338,7 +338,7 @@ ext4_fsblk_t ext4_inode_table(struct super_block *sb,
 __u32 ext4_free_group_clusters(struct super_block *sb,
 			       struct ext4_group_desc *bg)
 {
-	return le16_to_cpu(bg->bg_free_blocks_count_lo) |
+	return le16_to_cpu(READ_ONCE(bg->bg_free_blocks_count_lo)) |
 		(EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT ?
 		 (__u32)le16_to_cpu(bg->bg_free_blocks_count_hi) << 16 : 0);
 }
@@ -394,7 +394,7 @@ void ext4_inode_table_set(struct super_block *sb,
 void ext4_free_group_clusters_set(struct super_block *sb,
 				  struct ext4_group_desc *bg, __u32 count)
 {
-	bg->bg_free_blocks_count_lo = cpu_to_le16((__u16)count);
+	WRITE_ONCE(bg->bg_free_blocks_count_lo, cpu_to_le16((__u16)count));
 	if (EXT4_DESC_SIZE(sb) >= EXT4_MIN_DESC_SIZE_64BIT)
 		bg->bg_free_blocks_count_hi = cpu_to_le16(count >> 16);
 }
--