Commit 68f23b89067f ("memcg: fix a crash in wb_workfn when a device
disappears") try to handle bdi->dev beening NULL by adding bdi_dev_name().
But, bdi->dev can be freed and set as 'NULL' after bdi_dev_name()
think the value is valid. Then it can cause use-after-free for dev
or kobj->name.
After protecting the bdi->dev with lock, the race can be fixed thoroughly.
Here, we just need to replace bdi_dev_name() with bdi_get_dev_name().
Fixes: 68f23b89067f ("memcg: fix a crash in wb_workfn when a device disappears")
Signed-off-by: Yufen Yu <yuyufen@xxxxxxxxxx>
---
fs/fs-writeback.c | 4 +++-
include/trace/events/writeback.h | 38 ++++++++++++++------------------
2 files changed, 20 insertions(+), 22 deletions(-)
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 76ac9c7d32ec..8d36c256560c 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -2062,8 +2062,10 @@ void wb_workfn(struct work_struct *work)
struct bdi_writeback *wb = container_of(to_delayed_work(work),
struct bdi_writeback, dwork);
long pages_written;
+ char dname[BDI_DEV_NAME_LEN];
- set_worker_desc("flush-%s", bdi_dev_name(wb->bdi));
+ set_worker_desc("flush-%s",
+ bdi_get_dev_name(wb->bdi, dname, BDI_DEV_NAME_LEN));
current->flags |= PF_SWAPWRITE;
if (likely(!current_is_workqueue_rescuer() ||
diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
index d94def25e4dc..4767a5ab5e36 100644
--- a/include/trace/events/writeback.h
+++ b/include/trace/events/writeback.h
@@ -66,9 +66,8 @@ DECLARE_EVENT_CLASS(writeback_page_template,
),
TP_fast_assign(
- strscpy_pad(__entry->name,
- bdi_dev_name(mapping ? inode_to_bdi(mapping->host) :
- NULL), 32);
+ bdi_get_dev_name(mapping ? inode_to_bdi(mapping->host) : NULL,
+ __entry->name, 32);
__entry->ino = mapping ? mapping->host->i_ino : 0;
__entry->index = page->index;
),
@@ -111,7 +110,7 @@ DECLARE_EVENT_CLASS(writeback_dirty_inode_template,
struct backing_dev_info *bdi = inode_to_bdi(inode);
/* may be called for files on pseudo FSes w/ unregistered bdi */
- strscpy_pad(__entry->name, bdi_dev_name(bdi), 32);
+ bdi_get_dev_name(bdi, __entry->name, 32);
__entry->ino = inode->i_ino;
__entry->state = inode->i_state;
__entry->flags = flags;
@@ -192,7 +191,7 @@ TRACE_EVENT(inode_foreign_history,
),
TP_fast_assign(
- strncpy(__entry->name, bdi_dev_name(inode_to_bdi(inode)), 32);
+ bdi_get_dev_name(inode_to_bdi(inode), __entry->name, 32);
__entry->ino = inode->i_ino;
__entry->cgroup_ino = __trace_wbc_assign_cgroup(wbc);
__entry->history = history;
@@ -221,7 +220,7 @@ TRACE_EVENT(inode_switch_wbs,
),
TP_fast_assign(
- strncpy(__entry->name, bdi_dev_name(old_wb->bdi), 32);
+ bdi_get_dev_name(old_wb->bdi, __entry->name, 32);
__entry->ino = inode->i_ino;
__entry->old_cgroup_ino = __trace_wb_assign_cgroup(old_wb);
__entry->new_cgroup_ino = __trace_wb_assign_cgroup(new_wb);
@@ -254,7 +253,7 @@ TRACE_EVENT(track_foreign_dirty,
struct address_space *mapping = page_mapping(page);
struct inode *inode = mapping ? mapping->host : NULL;
- strncpy(__entry->name, bdi_dev_name(wb->bdi), 32);
+ bdi_get_dev_name(wb->bdi, __entry->name, 32);
__entry->bdi_id = wb->bdi->id;
__entry->ino = inode ? inode->i_ino : 0;
__entry->memcg_id = wb->memcg_css->id;
@@ -287,7 +286,7 @@ TRACE_EVENT(flush_foreign,
),
TP_fast_assign(
- strncpy(__entry->name, bdi_dev_name(wb->bdi), 32);
+ bdi_get_dev_name(wb->bdi, __entry->name, 32);
__entry->cgroup_ino = __trace_wb_assign_cgroup(wb);
__entry->frn_bdi_id = frn_bdi_id;
__entry->frn_memcg_id = frn_memcg_id;
@@ -316,8 +315,7 @@ DECLARE_EVENT_CLASS(writeback_write_inode_template,
),
TP_fast_assign(
- strscpy_pad(__entry->name,
- bdi_dev_name(inode_to_bdi(inode)), 32);
+ bdi_get_dev_name(inode_to_bdi(inode), __entry->name, 32);
__entry->ino = inode->i_ino;
__entry->sync_mode = wbc->sync_mode;
__entry->cgroup_ino = __trace_wbc_assign_cgroup(wbc);
@@ -360,7 +358,7 @@ DECLARE_EVENT_CLASS(writeback_work_class,
__field(ino_t, cgroup_ino)
),
TP_fast_assign(
- strscpy_pad(__entry->name, bdi_dev_name(wb->bdi), 32);
+ bdi_get_dev_name(wb->bdi, __entry->name, 32);
__entry->nr_pages = work->nr_pages;
__entry->sb_dev = work->sb ? work->sb->s_dev : 0;
__entry->sync_mode = work->sync_mode;
@@ -413,7 +411,7 @@ DECLARE_EVENT_CLASS(writeback_class,
__field(ino_t, cgroup_ino)
),
TP_fast_assign(
- strscpy_pad(__entry->name, bdi_dev_name(wb->bdi), 32);
+ bdi_get_dev_name(wb->bdi, __entry->name, 32);
__entry->cgroup_ino = __trace_wb_assign_cgroup(wb);
),
TP_printk("bdi %s: cgroup_ino=%lu",
@@ -435,7 +433,7 @@ TRACE_EVENT(writeback_bdi_register,
__array(char, name, 32)
),
TP_fast_assign(
- strscpy_pad(__entry->name, bdi_dev_name(bdi), 32);
+ bdi_get_dev_name(bdi, __entry->name, 32);
),
TP_printk("bdi %s",
__entry->name
@@ -460,7 +458,7 @@ DECLARE_EVENT_CLASS(wbc_class,
),
TP_fast_assign(
- strscpy_pad(__entry->name, bdi_dev_name(bdi), 32);
+ bdi_get_dev_name(bdi, __entry->name, 32);
__entry->nr_to_write = wbc->nr_to_write;
__entry->pages_skipped = wbc->pages_skipped;
__entry->sync_mode = wbc->sync_mode;
@@ -511,7 +509,7 @@ TRACE_EVENT(writeback_queue_io,
),
TP_fast_assign(
unsigned long *older_than_this = work->older_than_this;
- strscpy_pad(__entry->name, bdi_dev_name(wb->bdi), 32);
+ bdi_get_dev_name(wb->bdi, __entry->name, 32);
__entry->older = older_than_this ? *older_than_this : 0;
__entry->age = older_than_this ?
(jiffies - *older_than_this) * 1000 / HZ : -1;
@@ -597,7 +595,7 @@ TRACE_EVENT(bdi_dirty_ratelimit,
),
TP_fast_assign(
- strscpy_pad(__entry->bdi, bdi_dev_name(wb->bdi), 32);
+ bdi_get_dev_name(wb->bdi, __entry->bdi, 32);
__entry->write_bw = KBps(wb->write_bandwidth);
__entry->avg_write_bw = KBps(wb->avg_write_bandwidth);
__entry->dirty_rate = KBps(dirty_rate);
@@ -662,7 +660,7 @@ TRACE_EVENT(balance_dirty_pages,
TP_fast_assign(
unsigned long freerun = (thresh + bg_thresh) / 2;
- strscpy_pad(__entry->bdi, bdi_dev_name(wb->bdi), 32);
+ bdi_get_dev_name(wb->bdi, __entry->bdi, 32);
__entry->limit = global_wb_domain.dirty_limit;
__entry->setpoint = (global_wb_domain.dirty_limit +
@@ -722,8 +720,7 @@ TRACE_EVENT(writeback_sb_inodes_requeue,
),
TP_fast_assign(
- strscpy_pad(__entry->name,
- bdi_dev_name(inode_to_bdi(inode)), 32);
+ bdi_get_dev_name(inode_to_bdi(inode), __entry->name, 32);
__entry->ino = inode->i_ino;
__entry->state = inode->i_state;
__entry->dirtied_when = inode->dirtied_when;
@@ -796,8 +793,7 @@ DECLARE_EVENT_CLASS(writeback_single_inode_template,
),
TP_fast_assign(
- strscpy_pad(__entry->name,
- bdi_dev_name(inode_to_bdi(inode)), 32);
+ bdi_get_dev_name(inode_to_bdi(inode), __entry->name, 32);
__entry->ino = inode->i_ino;
__entry->state = inode->i_state;
__entry->dirtied_when = inode->dirtied_when;
--
2.17.2
