2022-03-16 14:56:36

by Dongliang Mu

Subject: [PATCH] fs: erofs: remember if kobject_init_and_add was done

From: Dongliang Mu <[email protected]>

Syzkaller hit 'WARNING: kobject bug in erofs_unregister_sysfs'. This bug
is triggered by injecting fault in kobject_init_and_add of
erofs_unregister_sysfs.

Fix this by remembering if kobject_init_and_add is successful.

Note that I've tested the patch and the crash does not occur any more.

Reported-by: syzkaller <[email protected]>
Signed-off-by: Dongliang Mu <[email protected]>
---
fs/erofs/internal.h | 1 +
fs/erofs/sysfs.c | 9 ++++++---
2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
index 5aa2cf2c2f80..9e20665e3f68 100644
--- a/fs/erofs/internal.h
+++ b/fs/erofs/internal.h
@@ -144,6 +144,7 @@ struct erofs_sb_info {
u32 feature_incompat;

/* sysfs support */
+ bool s_sysfs_inited;
struct kobject s_kobj; /* /sys/fs/erofs/<devname> */
struct completion s_kobj_unregister;
};
diff --git a/fs/erofs/sysfs.c b/fs/erofs/sysfs.c
index dac252bc9228..2b48a4df19b4 100644
--- a/fs/erofs/sysfs.c
+++ b/fs/erofs/sysfs.c
@@ -209,6 +209,7 @@ int erofs_register_sysfs(struct super_block *sb)
"%s", sb->s_id);
if (err)
goto put_sb_kobj;
+ sbi->s_sysfs_inited = true;
return 0;

put_sb_kobj:
@@ -221,9 +222,11 @@ void erofs_unregister_sysfs(struct super_block *sb)
{
struct erofs_sb_info *sbi = EROFS_SB(sb);

- kobject_del(&sbi->s_kobj);
- kobject_put(&sbi->s_kobj);
- wait_for_completion(&sbi->s_kobj_unregister);
+ if (sbi->s_sysfs_inited) {
+ kobject_del(&sbi->s_kobj);
+ kobject_put(&sbi->s_kobj);
+ wait_for_completion(&sbi->s_kobj_unregister);
+ }
}

int __init erofs_init_sysfs(void)
--
2.25.1

2022-03-17 03:25:04

by Gao Xiang

Subject: Re: [PATCH] fs: erofs: remember if kobject_init_and_add was done

On Tue, Mar 15, 2022 at 03:51:52PM +0800, Dongliang Mu wrote:
> From: Dongliang Mu <[email protected]>
>
> Syzkaller hit 'WARNING: kobject bug in erofs_unregister_sysfs'. This bug
> is triggered by injecting fault in kobject_init_and_add of
> erofs_unregister_sysfs.
>
> Fix this by remembering if kobject_init_and_add is successful.
>
> Note that I've tested the patch and the crash does not occur any more.
>
> Reported-by: syzkaller <[email protected]>
> Signed-off-by: Dongliang Mu <[email protected]>

Thanks for the effort!

Fixes: 168e9a76200c ("erofs: add sysfs interface")
Reviewed-by: Gao Xiang <[email protected]>

Thanks,
Gao Xiang

2022-03-17 06:14:34

by Huang Jianan

Subject: Re: [PATCH] fs: erofs: remember if kobject_init_and_add was done

在 2022/3/15 15:51, Dongliang Mu 写道:
> From: Dongliang Mu <[email protected]>
>
> Syzkaller hit 'WARNING: kobject bug in erofs_unregister_sysfs'. This bug
> is triggered by injecting fault in kobject_init_and_add of
> erofs_unregister_sysfs.
>
> Fix this by remembering if kobject_init_and_add is successful.
>
> Note that I've tested the patch and the crash does not occur any more.
>
> Reported-by: syzkaller <[email protected]>
> Signed-off-by: Dongliang Mu <[email protected]>
> ---
> fs/erofs/internal.h | 1 +
> fs/erofs/sysfs.c | 9 ++++++---
> 2 files changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
> index 5aa2cf2c2f80..9e20665e3f68 100644
> --- a/fs/erofs/internal.h
> +++ b/fs/erofs/internal.h
> @@ -144,6 +144,7 @@ struct erofs_sb_info {
> u32 feature_incompat;
>
> /* sysfs support */
> + bool s_sysfs_inited;

Hi Dongliang,

How about using sbi->s_kobj.state_in_sysfs to avoid adding a extra
member in sbi ?

Thanks,
Jianan

> struct kobject s_kobj; /* /sys/fs/erofs/<devname> */
> struct completion s_kobj_unregister;
> };
> diff --git a/fs/erofs/sysfs.c b/fs/erofs/sysfs.c
> index dac252bc9228..2b48a4df19b4 100644
> --- a/fs/erofs/sysfs.c
> +++ b/fs/erofs/sysfs.c
> @@ -209,6 +209,7 @@ int erofs_register_sysfs(struct super_block *sb)
> "%s", sb->s_id);
> if (err)
> goto put_sb_kobj;
> + sbi->s_sysfs_inited = true;
> return 0;
>
> put_sb_kobj:
> @@ -221,9 +222,11 @@ void erofs_unregister_sysfs(struct super_block *sb)
> {
> struct erofs_sb_info *sbi = EROFS_SB(sb);
>
> - kobject_del(&sbi->s_kobj);
> - kobject_put(&sbi->s_kobj);
> - wait_for_completion(&sbi->s_kobj_unregister);
> + if (sbi->s_sysfs_inited) {
> + kobject_del(&sbi->s_kobj);
> + kobject_put(&sbi->s_kobj);
> + wait_for_completion(&sbi->s_kobj_unregister);
> + }
> }
>
> int __init erofs_init_sysfs(void)