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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: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This commit is contained in:
Chao Yu 2018-05-28 16:57:32 +08:00 committed by Jaegeuk Kim
parent aec2f729fc
commit 250dbf5151
1 changed files with 18 additions and 1 deletions
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19
fs/f2fs/sysfs.c
View File

@ -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 @@ out:
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)
{