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

Dongliang Mu
2022-03-15T07:52:34Z

From: Dongliang Mu <mudongliangabcd@gmail.com>

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 <syzkaller@googlegroups.com>
Signed-off-by: Dongliang Mu <mudongliangabcd@gmail.com>
---
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