On Tue, Sep 7, 2021 at 12:47 AM Pavel Skripkin <paskripkin@xxxxxxxxx> wrote: > > On 9/6/21 18:56, Pavel Skripkin wrote: > > On 9/6/21 08:43, Dongliang Mu wrote: > >> On Mon, Sep 6, 2021 at 12:13 PM Dongliang Mu <mudongliangabcd@xxxxxxxxx> wrote: > >>> > >>> The commit 8fd0c1b0647a ("nilfs2: fix memory leak in > >>> nilfs_sysfs_delete_device_group") adds a kobject_put to free the leaking > >>> object name. However, it is incomplete to only add kobject_put in the > >>> nilfs_sysfs_delete_device_group. The function > >>> nilfs_sysfs_create_device_group also needs the kobject_put to > >>> free the object name in the error handling part. > >>> > >>> Fix this by adding kobject_put in the error handling code of > >>> nilfs_sysfs_create_device_group. > >> > >> Even after I add this patch, my local syzkaller still reports this > >> memory leak one hour later. Therefore, there are some other paths or > >> magics which can trigger the memory leak. I need to dig deeper. > >> > >> Pavel, do you have any idea about this crash report? > >> > >> BUG: memory leak > >> unreferenced object 0xffff88804a1a8a60 (size 32): > >> comm "syz-executor", pid 14551, jiffies 4294960586 (age 14.780s) > >> hex dump (first 32 bytes): > >> 6c 6f 6f 70 35 00 00 00 00 00 00 00 00 00 00 00 loop5........... > >> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > >> backtrace: > >> [<ffffffff814750c6>] kstrdup+0x36/0x70 > >> [<ffffffff81475153>] kstrdup_const+0x53/0x80 > >> [<ffffffff822773a2>] kvasprintf_const+0xc2/0x110 > >> [<ffffffff82337c5b>] kobject_set_name_vargs+0x3b/0xe0 > >> [<ffffffff823385ed>] kobject_init_and_add+0x6d/0xc0 > >> [<ffffffff81d2bd08>] nilfs_sysfs_create_device_group+0x98/0x3a0 > >> [<ffffffff81d14fc4>] init_nilfs+0x424/0x580 > >> [<ffffffff81d02962>] nilfs_mount+0x532/0x8c0 > >> [<ffffffff815c754b>] legacy_get_tree+0x2b/0x90 > >> [<ffffffff81565158>] vfs_get_tree+0x28/0x100 > >> [<ffffffff815a3a82>] path_mount+0xb92/0xfe0 > >> [<ffffffff815a3f71>] do_mount+0xa1/0xc0 > >> [<ffffffff815a4584>] __x64_sys_mount+0xf4/0x160 > >> [<ffffffff8433fd35>] do_syscall_64+0x35/0xb0 > >> [<ffffffff84400068>] entry_SYSCALL_64_after_hwframe+0x44/0xae > >> > >> > > > > Hi, Dongliang! > > > > > > This report says nothing to me... It shows, that there is missing > > kobject_put() somewhere. I think, we need a reproducer for this leak, > > otherwise only code review can help :( > > > > > > > > Hm, I guess, I see... We should call kobject_put() in case of > kobject_init_and_add() failure: > > lib/kobject.c:459 > > * If this function returns an error, kobject_put() must be called to > * properly clean up the memory associated with the object. This is the > > > so I suggest: > > diff --git a/fs/nilfs2/sysfs.c b/fs/nilfs2/sysfs.c > index 68e8d61e28dd..e8717f4ba2a1 100644 > --- a/fs/nilfs2/sysfs.c > +++ b/fs/nilfs2/sysfs.c > @@ -1026,6 +1026,7 @@ int nilfs_sysfs_create_device_group(struct > super_block *sb) kobject_del(&nilfs->ns_dev_kobj); > > free_dev_subgroups: > + kobject_put(&nilfs->ns_dev_kobj); > kfree(nilfs->ns_dev_subgroups); > > failed_create_device_group: > > > This patch should fix 2 memory leaks :) Yes. We should move kobject_put from the label cleanup_dev_kobject to free_dev_subgroups. However, I tried the syz reproducer just sent to you. The memory leak is still there. > > > > > With regards, > Pavel Skripkin