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/orphan.c |  2 +-
 fs/ext4/super.c  |  4 ++--
 mm/percpu.c      |  5 ++---
 mm/shmem.c       | 12 +++++++-----
 4 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/fs/ext4/orphan.c b/fs/ext4/orphan.c
index e5b47dda3317..08299b2a1b3b 100644
--- a/fs/ext4/orphan.c
+++ b/fs/ext4/orphan.c
@@ -293,7 +293,7 @@ int ext4_orphan_del(handle_t *handle, struct inode *inode)
 			mutex_unlock(&sbi->s_orphan_lock);
 			goto out_brelse;
 		}
-		NEXT_ORPHAN(i_prev) = ino_next;
+		WRITE_ONCE(NEXT_ORPHAN(i_prev), ino_next);
 		err = ext4_mark_iloc_dirty(handle, i_prev, &iloc2);
 		mutex_unlock(&sbi->s_orphan_lock);
 	}
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);
 }
diff --git a/mm/percpu.c b/mm/percpu.c
index 20d91af8c033..5c958a54da51 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1864,7 +1864,6 @@ void __percpu *pcpu_alloc_noprof(size_t size, size_t align, bool reserved,
 
 area_found:
 	pcpu_stats_area_alloc(chunk, size);
-	spin_unlock_irqrestore(&pcpu_lock, flags);
 
 	/* populate if not all pages are already there */
 	if (!is_atomic) {
@@ -1878,14 +1877,12 @@ void __percpu *pcpu_alloc_noprof(size_t size, size_t align, bool reserved,
 
 			ret = pcpu_populate_chunk(chunk, rs, re, pcpu_gfp);
 
-			spin_lock_irqsave(&pcpu_lock, flags);
 			if (ret) {
 				pcpu_free_area(chunk, off);
 				err = "failed to populate";
 				goto fail_unlock;
 			}
 			pcpu_chunk_populated(chunk, rs, re);
-			spin_unlock_irqrestore(&pcpu_lock, flags);
 		}
 
 		mutex_unlock(&pcpu_alloc_mutex);
@@ -1894,6 +1891,8 @@ void __percpu *pcpu_alloc_noprof(size_t size, size_t align, bool reserved,
 	if (pcpu_nr_empty_pop_pages < PCPU_EMPTY_POP_PAGES_LOW)
 		pcpu_schedule_balance_work();
 
+	spin_unlock_irqrestore(&pcpu_lock, flags);
+
 	/* clear the areas and return address relative to base address */
 	for_each_possible_cpu(cpu)
 		memset((void *)pcpu_chunk_addr(chunk, cpu, 0) + off, 0, size);
diff --git a/mm/shmem.c b/mm/shmem.c
index 5a77acf6ac6a..1595f6e7688c 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1154,7 +1154,9 @@ static int shmem_getattr(struct mnt_idmap *idmap,
 	stat->attributes_mask |= (STATX_ATTR_APPEND |
 			STATX_ATTR_IMMUTABLE |
 			STATX_ATTR_NODUMP);
+	inode_lock_shared(inode);
 	generic_fillattr(idmap, request_mask, inode, stat);
+	inode_unlock_shared(inode);
 
 	if (shmem_is_huge(inode, 0, false, NULL, 0))
 		stat->blksize = HPAGE_PMD_SIZE;
@@ -3439,7 +3441,7 @@ shmem_mknod(struct mnt_idmap *idmap, struct inode *dir,
 	if (error)
 		goto out_iput;
 
-	dir->i_size += BOGO_DIRENT_SIZE;
+	i_size_write(dir, i_size_read(dir) + BOGO_DIRENT_SIZE);
 	inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
 	inode_inc_iversion(dir);
 	d_instantiate(dentry, inode);
@@ -3526,7 +3528,7 @@ static int shmem_link(struct dentry *old_dentry, struct inode *dir,
 		goto out;
 	}
 
-	dir->i_size += BOGO_DIRENT_SIZE;
+	i_size_write(dir, i_size_read(dir) + BOGO_DIRENT_SIZE);
 	inode_set_mtime_to_ts(dir,
 			      inode_set_ctime_to_ts(dir, inode_set_ctime_current(inode)));
 	inode_inc_iversion(dir);
@@ -3639,8 +3641,8 @@ static int shmem_rename2(struct mnt_idmap *idmap,
 		inc_nlink(new_dir);
 	}
 
-	old_dir->i_size -= BOGO_DIRENT_SIZE;
-	new_dir->i_size += BOGO_DIRENT_SIZE;
+	i_size_write(old_dir, i_size_read(old_dir) - BOGO_DIRENT_SIZE);
+	i_size_write(new_dir, i_size_read(new_dir) + BOGO_DIRENT_SIZE);
 	simple_rename_timestamp(old_dir, old_dentry, new_dir, new_dentry);
 	inode_inc_iversion(old_dir);
 	inode_inc_iversion(new_dir);
@@ -3694,7 +3696,7 @@ static int shmem_symlink(struct mnt_idmap *idmap, struct inode *dir,
 		folio_unlock(folio);
 		folio_put(folio);
 	}
-	dir->i_size += BOGO_DIRENT_SIZE;
+	i_size_write(dir, i_size_read(dir) + BOGO_DIRENT_SIZE);
 	inode_set_mtime_to_ts(dir, inode_set_ctime_current(dir));
 	inode_inc_iversion(dir);
 	d_instantiate(dentry, inode);
--