Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 250dbf51 authored by Chao Yu's avatar Chao Yu Committed by Jaegeuk Kim
Browse files

f2fs: fix to avoid race during access gc_thread pointer 



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: default avatarChao Yu <yuchao0@huawei.com>
Signed-off-by: default avatarJaegeuk Kim <jaegeuk@kernel.org>
parent aec2f729

fs/f2fs/sysfs.c

+18 −1
Original line number Diff line number Diff line
@@ -165,7 +165,7 @@ static ssize_t f2fs_sbi_show(struct f2fs_attr *a, 
	return snprintf(buf, PAGE_SIZE, "%u\n", *ui);

}



static ssize_t f2fs_sbi_store(struct f2fs_attr *a,

static ssize_t __f2fs_sbi_store(struct f2fs_attr *a,

			struct f2fs_sb_info *sbi,

			const char *buf, size_t count)

{
@@ -278,6 +278,23 @@ static ssize_t f2fs_sbi_store(struct f2fs_attr *a, 
	return count;

}



static ssize_t f2fs_sbi_store(struct f2fs_attr *a,

			struct f2fs_sb_info *sbi,

			const char *buf, size_t count)

{

	ssize_t ret;

	bool gc_entry = (!strcmp(a->attr.name, "gc_urgent") ||

					a->struct_type == GC_THREAD);



	if (gc_entry)

		down_read(&sbi->sb->s_umount);

	ret = __f2fs_sbi_store(a, sbi, buf, count);

	if (gc_entry)

		up_read(&sbi->sb->s_umount);



	return ret;

}



static ssize_t f2fs_attr_show(struct kobject *kobj,

				struct attribute *attr, char *buf)

{