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 <[email protected]>
---
v2:
- fix to cover __struct_ptr() with sb->s_umount suggested by Jaegeuk.
fs/f2fs/sysfs.c | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)
diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
index 7432192ebe17..79f4e4ac8200 100644
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -168,7 +168,7 @@ 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)
{
@@ -261,6 +261,22 @@ 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 = (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)
{
--
2.17.0.391.g1f1cddd558b5
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