[PATCH v2 6/7] memcg: fix crash in wb_workfn when bdi unregister
From: Yufen Yu <hidden>
Date: 2020-02-26 11:11:51
Also in:
linux-fsdevel
Subsystem:
filesystems (vfs and infrastructure), page cache, the rest, tracing · Maintainers:
Alexander Viro, Christian Brauner, Matthew Wilcox, Linus Torvalds, Steven Rostedt, Masami Hiramatsu
To fix crash in wb_workfn when bdi_unreigster(), commit 68f23b89067f
("memcg: fix a crash in wb_workfn when a device disappears") has
created bdi_dev_name() to handle bdi->dev beening NULL. But, bdi->dev
can be freed after bdi_dev_name() return successly, which may cause
use-after-free for dev or kobj->name.
After protecting bdi->dev lifetimes by rcu lock, we can use
bdi_get_dev_name() to copy name safely.
Fixes: 68f23b89067f ("memcg: fix a crash in wb_workfn when a device disappears")
Signed-off-by: Yufen Yu <redacted>
---
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..b8098009e0dc 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)); + bdi_get_dev_name(wb->bdi, dname, BDI_DEV_NAME_LEN); + set_worker_desc("flush-%s", dname); 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;
--
2.16.2.dirty