[PATCH 0/6] nilfs2: fix incorrect usage of kobject

[PATCH 0/6] nilfs2: fix incorrect usage of kobject

[Nanyong Sun]

This patchset fix the memory leak problems and NULL pointer problem
caused by incorrect usage of kobject in nilfs2 sysfs driver.

Nanyong Sun (6):
  nilfs2: fix memory leak in nilfs_sysfs_create_device_group
  nilfs2: fix NULL pointer in nilfs_##name##_attr_release
  nilfs2: fix memory leak in nilfs_sysfs_create_##name##_group
  nilfs2: fix memory leak in nilfs_sysfs_delete_##name##_group
  nilfs2: fix memory leak in nilfs_sysfs_create_snapshot_group
  nilfs2: fix memory leak in nilfs_sysfs_delete_snapshot_group

 fs/nilfs2/sysfs.c | 26 +++++++++++---------------
 1 file changed, 11 insertions(+), 15 deletions(-)

-- 
2.18.0.huawei.25

[PATCH 1/6] nilfs2: fix memory leak in nilfs_sysfs_create_device_group

[Nanyong Sun]

Reported by syzkaller:
BUG: memory leak
unreferenced object 0xffff888100ca8988 (size 8):
comm "syz-executor.1", pid 1930, jiffies 4294745569 (age 18.052s)
hex dump (first 8 bytes):
6c 6f 6f 70 31 00 ff ff loop1...
backtrace:
[<000000009d9e0ac4>] slab_alloc_node mm/slub.c:2972 [inline]
[<000000009d9e0ac4>] slab_alloc mm/slub.c:2980 [inline]
[<000000009d9e0ac4>] __kmalloc_track_caller+0x164/0x330 mm/slub.c:4644
[<00000000b1825477>] kstrdup+0x36/0x70 mm/util.c:60
[<00000000fa081499>] kstrdup_const+0x35/0x60 mm/util.c:83
[<0000000024d13570>] kvasprintf_const+0xf1/0x180 lib/kasprintf.c:48
[<0000000024b69715>] kobject_set_name_vargs+0x56/0x150 lib/kobject.c:289
[<000000003fedac3d>] kobject_add_varg lib/kobject.c:384 [inline]
[<000000003fedac3d>] kobject_init_and_add+0xc9/0x150 lib/kobject.c:473
[<000000002795bd99>] nilfs_sysfs_create_device_group+0x150/0x7d0 fs/nilfs2/sysfs.c:986
[<00000000567fa12d>] init_nilfs+0xa21/0xea0 fs/nilfs2/the_nilfs.c:637
[<00000000082e7458>] nilfs_fill_super fs/nilfs2/super.c:1046 [inline]
[<00000000082e7458>] nilfs_mount+0x7b4/0xe80 fs/nilfs2/super.c:1316
[<00000000adc3fd88>] legacy_get_tree+0x105/0x210 fs/fs_context.c:592
[<00000000a98c45b8>] vfs_get_tree+0x8e/0x2d0 fs/super.c:1498
[<00000000e96282d3>] do_new_mount fs/namespace.c:2905 [inline]
[<00000000e96282d3>] path_mount+0xf9b/0x1990 fs/namespace.c:3235
[<000000003d2eb1b0>] do_mount+0xea/0x100 fs/namespace.c:3248
[<00000000e1ce771a>] __do_sys_mount fs/namespace.c:3456 [inline]
[<00000000e1ce771a>] __se_sys_mount fs/namespace.c:3433 [inline]
[<00000000e1ce771a>] __x64_sys_mount+0x14b/0x1f0 fs/namespace.c:3433
[<000000007c7f81e8>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
[<000000007c7f81e8>] do_syscall_64+0x3b/0x90 arch/x86/entry/common.c:80
[<00000000fd23ff06>] entry_SYSCALL_64_after_hwframe+0x44/0xae

If kobject_init_and_add return with error, then the cleanup of kobject
is needed because memory may be allocated in kobject_init_and_add
without freeing.
And the place of cleanup_dev_kobject should use kobject_put to free
the memory associated with the kobject. As the section "Kobject removal"
of "Documentation/core-api/kobject.rst" says, kobject_del() just makes
the kobject "invisible", but it is not cleaned up. And no more cleanup
will do after cleanup_dev_kobject, so kobject_put is needed here.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Nanyong Sun <sunnanyong@huawei.com>
---
 fs/nilfs2/sysfs.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/fs/nilfs2/sysfs.c b/fs/nilfs2/sysfs.c
index 68e8d61e28dd..d2d8ea89937a 100644
--- a/fs/nilfs2/sysfs.c
+++ b/fs/nilfs2/sysfs.c
@@ -986,7 +986,7 @@ int nilfs_sysfs_create_device_group(struct super_block *sb)
 	err = kobject_init_and_add(&nilfs->ns_dev_kobj, &nilfs_dev_ktype, NULL,
 				    "%s", sb->s_id);
 	if (err)
-		goto free_dev_subgroups;
+		goto cleanup_dev_kobject;
 
 	err = nilfs_sysfs_create_mounted_snapshots_group(nilfs);
 	if (err)
@@ -1023,9 +1023,7 @@ int nilfs_sysfs_create_device_group(struct super_block *sb)
 	nilfs_sysfs_delete_mounted_snapshots_group(nilfs);
 
 cleanup_dev_kobject:
-	kobject_del(&nilfs->ns_dev_kobj);
-
-free_dev_subgroups:
+	kobject_put(&nilfs->ns_dev_kobj);
 	kfree(nilfs->ns_dev_subgroups);
 
 failed_create_device_group:
-- 
2.18.0.huawei.25

[PATCH 2/6] nilfs2: fix NULL pointer in nilfs_##name##_attr_release

[Nanyong Sun]

In nilfs_##name##_attr_release, kobj->parent should not be
referenced because it is a NULL pointer. The release() method of
kobject is always called in kobject_put(kobj), in the implementation
of kobject_put(), the kobj->parent will be assigned as NULL before
call the release() method. So just use kobj to get the subgroups,
which is more efficient and can fix a NULL pointer reference problem.

Signed-off-by: Nanyong Sun <sunnanyong@huawei.com>
---
 fs/nilfs2/sysfs.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/fs/nilfs2/sysfs.c b/fs/nilfs2/sysfs.c
index d2d8ea89937a..ec85ac53720d 100644
--- a/fs/nilfs2/sysfs.c
+++ b/fs/nilfs2/sysfs.c
@@ -51,11 +51,9 @@ static const struct sysfs_ops nilfs_##name##_attr_ops = { \
 #define NILFS_DEV_INT_GROUP_TYPE(name, parent_name) \
 static void nilfs_##name##_attr_release(struct kobject *kobj) \
 { \
-	struct nilfs_sysfs_##parent_name##_subgroups *subgroups; \
-	struct the_nilfs *nilfs = container_of(kobj->parent, \
-						struct the_nilfs, \
-						ns_##parent_name##_kobj); \
-	subgroups = nilfs->ns_##parent_name##_subgroups; \
+	struct nilfs_sysfs_##parent_name##_subgroups *subgroups = container_of(kobj, \
+						struct nilfs_sysfs_##parent_name##_subgroups, \
+						sg_##name##_kobj); \
 	complete(&subgroups->sg_##name##_kobj_unregister); \
 } \
 static struct kobj_type nilfs_##name##_ktype = { \
-- 
2.18.0.huawei.25

[PATCH 3/6] nilfs2: fix memory leak in nilfs_sysfs_create_##name##_group

[Nanyong Sun]

If kobject_init_and_add return with error, kobject_put() is needed
here to avoid memory leak, because kobject_init_and_add may return
error without freeing the memory associated with the kobject it allocated.

Signed-off-by: Nanyong Sun <sunnanyong@huawei.com>
---
 fs/nilfs2/sysfs.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/nilfs2/sysfs.c b/fs/nilfs2/sysfs.c
index ec85ac53720d..6305e4ef7e39 100644
--- a/fs/nilfs2/sysfs.c
+++ b/fs/nilfs2/sysfs.c
@@ -79,8 +79,8 @@ static int nilfs_sysfs_create_##name##_group(struct the_nilfs *nilfs) \
 	err = kobject_init_and_add(kobj, &nilfs_##name##_ktype, parent, \
 				    #name); \
 	if (err) \
-		return err; \
-	return 0; \
+		kobject_put(kobj); \
+	return err; \
 } \
 static void nilfs_sysfs_delete_##name##_group(struct the_nilfs *nilfs) \
 { \
-- 
2.18.0.huawei.25

[PATCH 4/6] nilfs2: fix memory leak in nilfs_sysfs_delete_##name##_group

[Nanyong Sun]

The kobject_put() should be used to cleanup the memory associated with
the kobject insead of kobject_del. See the section "Kobject removal"
of "Documentation/core-api/kobject.rst".

Signed-off-by: Nanyong Sun <sunnanyong@huawei.com>
---
 fs/nilfs2/sysfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/nilfs2/sysfs.c b/fs/nilfs2/sysfs.c
index 6305e4ef7e39..d989e6500bd7 100644
--- a/fs/nilfs2/sysfs.c
+++ b/fs/nilfs2/sysfs.c
@@ -84,7 +84,7 @@ static int nilfs_sysfs_create_##name##_group(struct the_nilfs *nilfs) \
 } \
 static void nilfs_sysfs_delete_##name##_group(struct the_nilfs *nilfs) \
 { \
-	kobject_del(&nilfs->ns_##parent_name##_subgroups->sg_##name##_kobj); \
+	kobject_put(&nilfs->ns_##parent_name##_subgroups->sg_##name##_kobj); \
 }
 
 /************************************************************************
-- 
2.18.0.huawei.25

[PATCH 5/6] nilfs2: fix memory leak in nilfs_sysfs_create_snapshot_group

[Nanyong Sun]

If kobject_init_and_add returns with error, kobject_put() is needed
here to avoid memory leak, because kobject_init_and_add may return
error without freeing the memory associated with the kobject it allocated.

Signed-off-by: Nanyong Sun <sunnanyong@huawei.com>
---
 fs/nilfs2/sysfs.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/nilfs2/sysfs.c b/fs/nilfs2/sysfs.c
index d989e6500bd7..5ba87573ad3b 100644
--- a/fs/nilfs2/sysfs.c
+++ b/fs/nilfs2/sysfs.c
@@ -195,9 +195,9 @@ int nilfs_sysfs_create_snapshot_group(struct nilfs_root *root)
 	}
 
 	if (err)
-		return err;
+		kobject_put(&root->snapshot_kobj);
 
-	return 0;
+	return err;
 }
 
 void nilfs_sysfs_delete_snapshot_group(struct nilfs_root *root)
-- 
2.18.0.huawei.25

[PATCH 6/6] nilfs2: fix memory leak in nilfs_sysfs_delete_snapshot_group

[Nanyong Sun]

Kobject_put() should be used to cleanup the memory associated with
the kobject insead of kobject_del(). See the section "Kobject removal"
of "Documentation/core-api/kobject.rst".

Signed-off-by: Nanyong Sun <sunnanyong@huawei.com>
---
 fs/nilfs2/sysfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/nilfs2/sysfs.c b/fs/nilfs2/sysfs.c
index 5ba87573ad3b..62f8a7ac19c8 100644
--- a/fs/nilfs2/sysfs.c
+++ b/fs/nilfs2/sysfs.c
@@ -202,7 +202,7 @@ int nilfs_sysfs_create_snapshot_group(struct nilfs_root *root)
 
 void nilfs_sysfs_delete_snapshot_group(struct nilfs_root *root)
 {
-	kobject_del(&root->snapshot_kobj);
+	kobject_put(&root->snapshot_kobj);
 }
 
 /************************************************************************
-- 
2.18.0.huawei.25

Re: [PATCH 0/6] nilfs2: fix incorrect usage of kobject

[Ryusuke Konishi]

Hi, Nanyong

Thank you so much for sending this patchset.  I will review each and
send them upstream if applicable as is.

Thanks,
Ryusuke Konishi

On Tue, Jun 29, 2021 at 10:54 AM Nanyong Sun <sunnanyong@huawei.com> wrote:
>
> This patchset fix the memory leak problems and NULL pointer problem
> caused by incorrect usage of kobject in nilfs2 sysfs driver.
>
> Nanyong Sun (6):
>   nilfs2: fix memory leak in nilfs_sysfs_create_device_group
>   nilfs2: fix NULL pointer in nilfs_##name##_attr_release
>   nilfs2: fix memory leak in nilfs_sysfs_create_##name##_group
>   nilfs2: fix memory leak in nilfs_sysfs_delete_##name##_group
>   nilfs2: fix memory leak in nilfs_sysfs_create_snapshot_group
>   nilfs2: fix memory leak in nilfs_sysfs_delete_snapshot_group
>
>  fs/nilfs2/sysfs.c | 26 +++++++++++---------------
>  1 file changed, 11 insertions(+), 15 deletions(-)
>
> --
> 2.18.0.huawei.25
>

[PATCH 4/6] nilfs2: fix memory leak in nilfs_sysfs_delete_##name##_group

[Ryusuke Konishi]

From: Nanyong Sun <sunnanyong@huawei.com>

The kobject_put() should be used to cleanup the memory associated with
the kobject instead of kobject_del. See the section "Kobject removal"
of "Documentation/core-api/kobject.rst".

Link: https://lkml.kernel.org/r/20210629022556.3985106-5-sunnanyong@huawei.com
Signed-off-by: Nanyong Sun <sunnanyong@huawei.com>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
---
 fs/nilfs2/sysfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/nilfs2/sysfs.c b/fs/nilfs2/sysfs.c
index 5dc468ff5903..34893a57a7b9 100644
--- a/fs/nilfs2/sysfs.c
+++ b/fs/nilfs2/sysfs.c
@@ -97,7 +97,7 @@
 } \
 static void nilfs_sysfs_delete_##name##_group(struct the_nilfs *nilfs) \
 { \
-	kobject_del(&nilfs->ns_##parent_name##_subgroups->sg_##name##_kobj); \
+	kobject_put(&nilfs->ns_##parent_name##_subgroups->sg_##name##_kobj); \
 }
 
 /************************************************************************
-- 
1.8.3.1