On 05/08, Chao Yu wrote: > Thread A Thread B > - f2fs_remount > - stop_gc_thread > - f2fs_sbi_store > sbi->gc_thread = NULL; > access sbi->gc_thread->gc_* > > Previously, we allocate memory for sbi->gc_thread based on background > gc thread mount option, the memory can be released if we turn off > that mount option, but still there are several places access gc_thread > pointer without considering race condition, result in NULL point > dereference. > > In order to fix this issue, use sb->s_umount to exclude those operations. > > Signed-off-by: Chao Yu <yuch...@huawei.com> > --- > fs/f2fs/sysfs.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c > index f3c3fb4cbb0d..0aec4db7fa02 100644 > --- a/fs/f2fs/sysfs.c > +++ b/fs/f2fs/sysfs.c > @@ -179,6 +179,7 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a, > unsigned long t; > unsigned int *ui; > ssize_t ret; > + bool gc_entry = (a->struct_type == GC_THREAD); > > ptr = __struct_ptr(sbi, a->struct_type);
We need to cover __struct_ptr() here. > if (!ptr) > @@ -277,8 +278,14 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a, > return count; > } > > + if (gc_entry) > + down_read(&sbi->sb->s_umount); > + > *ui = t; > > + if (gc_entry) > + up_read(&sbi->sb->s_umount); > + > if (!strcmp(a->attr.name, "iostat_enable") && *ui == 0) > f2fs_reset_iostat(sbi); > return count; > -- > 2.17.0.391.g1f1cddd558b5
