* [PATCH v4 1/6] bdi: use bdi_dev_name() to get device name
2020-03-25 12:38 [PATCH v4 0/6] bdi: fix use-after-free for bdi device Yufen Yu
@ 2020-03-25 12:38 ` Yufen Yu
2020-03-25 12:38 ` [PATCH v4 2/6] bdi: protect bdi->dev with spinlock Yufen Yu
` (6 subsequent siblings)
7 siblings, 0 replies; 12+ messages in thread
From: Yufen Yu @ 2020-03-25 12:38 UTC (permalink / raw)
To: axboe, linux-block; +Cc: tj, jack, bvanassche, tytso, gregkh, hch
Use the common interface bdi_dev_name() to get device name.
Signed-off-by: Yufen Yu <yuyufen@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
block/bfq-iosched.c | 5 +++--
block/blk-cgroup.c | 2 +-
fs/ceph/debugfs.c | 2 +-
include/trace/events/wbt.h | 8 ++++----
4 files changed, 9 insertions(+), 8 deletions(-)
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 8c436abfaf14..94261b7d7181 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -4978,8 +4978,9 @@ bfq_set_next_ioprio_data(struct bfq_queue *bfqq, struct bfq_io_cq *bic)
ioprio_class = IOPRIO_PRIO_CLASS(bic->ioprio);
switch (ioprio_class) {
default:
- dev_err(bfqq->bfqd->queue->backing_dev_info->dev,
- "bfq: bad prio class %d\n", ioprio_class);
+ pr_err("bdi %s: bfq: bad prio class %d\n",
+ bdi_dev_name(bfqq->bfqd->queue->backing_dev_info),
+ ioprio_class);
/* fall through */
case IOPRIO_CLASS_NONE:
/*
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index a229b94d5390..be92405c6547 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -496,7 +496,7 @@ const char *blkg_dev_name(struct blkcg_gq *blkg)
{
/* some drivers (floppy) instantiate a queue w/o disk registered */
if (blkg->q->backing_dev_info->dev)
- return dev_name(blkg->q->backing_dev_info->dev);
+ return bdi_dev_name(blkg->q->backing_dev_info);
return NULL;
}
diff --git a/fs/ceph/debugfs.c b/fs/ceph/debugfs.c
index fb7cabd98e7b..1f8f3b631adb 100644
--- a/fs/ceph/debugfs.c
+++ b/fs/ceph/debugfs.c
@@ -271,7 +271,7 @@ void ceph_fs_debugfs_init(struct ceph_fs_client *fsc)
&congestion_kb_fops);
snprintf(name, sizeof(name), "../../bdi/%s",
- dev_name(fsc->sb->s_bdi->dev));
+ bdi_dev_name(fsc->sb->s_bdi));
fsc->debugfs_bdi =
debugfs_create_symlink("bdi",
fsc->client->debugfs_dir,
diff --git a/include/trace/events/wbt.h b/include/trace/events/wbt.h
index 37342a13c9cb..9996420d7ec4 100644
--- a/include/trace/events/wbt.h
+++ b/include/trace/events/wbt.h
@@ -33,7 +33,7 @@ TRACE_EVENT(wbt_stat,
),
TP_fast_assign(
- strlcpy(__entry->name, dev_name(bdi->dev),
+ strlcpy(__entry->name, bdi_dev_name(bdi),
ARRAY_SIZE(__entry->name));
__entry->rmean = stat[0].mean;
__entry->rmin = stat[0].min;
@@ -68,7 +68,7 @@ TRACE_EVENT(wbt_lat,
),
TP_fast_assign(
- strlcpy(__entry->name, dev_name(bdi->dev),
+ strlcpy(__entry->name, bdi_dev_name(bdi),
ARRAY_SIZE(__entry->name));
__entry->lat = div_u64(lat, 1000);
),
@@ -105,7 +105,7 @@ TRACE_EVENT(wbt_step,
),
TP_fast_assign(
- strlcpy(__entry->name, dev_name(bdi->dev),
+ strlcpy(__entry->name, bdi_dev_name(bdi),
ARRAY_SIZE(__entry->name));
__entry->msg = msg;
__entry->step = step;
@@ -141,7 +141,7 @@ TRACE_EVENT(wbt_timer,
),
TP_fast_assign(
- strlcpy(__entry->name, dev_name(bdi->dev),
+ strlcpy(__entry->name, bdi_dev_name(bdi),
ARRAY_SIZE(__entry->name));
__entry->status = status;
__entry->step = step;
--
2.17.2
^ permalink raw reply related [flat|nested] 12+ messages in thread* [PATCH v4 2/6] bdi: protect bdi->dev with spinlock
2020-03-25 12:38 [PATCH v4 0/6] bdi: fix use-after-free for bdi device Yufen Yu
2020-03-25 12:38 ` [PATCH v4 1/6] bdi: use bdi_dev_name() to get device name Yufen Yu
@ 2020-03-25 12:38 ` Yufen Yu
2020-03-25 12:38 ` [PATCH v4 3/6] bfq: fix potential kernel crash when print error info Yufen Yu
` (5 subsequent siblings)
7 siblings, 0 replies; 12+ messages in thread
From: Yufen Yu @ 2020-03-25 12:38 UTC (permalink / raw)
To: axboe, linux-block; +Cc: tj, jack, bvanassche, tytso, gregkh, hch
We have reported a kernel crash in __blkg_prfill_rwstat() for
use-after-free the bdi->dev. It tries to get the device name by
'bdi->dev', while the device and kobj->name has been freed by
bdi_unregister().
In fact, similar bug have been reported in wb_workfn when
bdi_unregister(). To fix it, 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 can cause use-after-free for
dev or kobj->name.
In this patch, we try to protect the 'bdi->dev' with spinlock to
avoid the race. A new helper function bdi_get_dev_name() is defined.
Then, the caller can get device name with this helper safely.
This patch is prepare for following patch to fix use-after-free bug.
Signed-off-by: Yufen Yu <yuyufen@huawei.com>
---
include/linux/backing-dev-defs.h | 1 +
include/linux/backing-dev.h | 28 ++++++++++++++++++++++++++++
mm/backing-dev.c | 9 +++++++--
3 files changed, 36 insertions(+), 2 deletions(-)
diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h
index 4fc87dee005a..c98dac4a7953 100644
--- a/include/linux/backing-dev-defs.h
+++ b/include/linux/backing-dev-defs.h
@@ -227,6 +227,7 @@ struct backing_dev_info {
#ifdef CONFIG_DEBUG_FS
struct dentry *debug_dir;
#endif
+ spinlock_t lock; /* protects dev */
};
enum {
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index f88197c1ffc2..010d80956442 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -19,6 +19,8 @@
#include <linux/backing-dev-defs.h>
#include <linux/slab.h>
+#define BDI_DEV_NAME_LEN 32
+
static inline struct backing_dev_info *bdi_get(struct backing_dev_info *bdi)
{
kref_get(&bdi->refcnt);
@@ -514,4 +516,30 @@ static inline const char *bdi_dev_name(struct backing_dev_info *bdi)
return dev_name(bdi->dev);
}
+/**
+ * bdi_get_dev_name - copy bdi device name into buffer
+ * @bdi: target bdi
+ * @dname: Where to copy the device name to
+ * @len: size of destination buffer
+ */
+static inline char *bdi_get_dev_name(struct backing_dev_info *bdi,
+ char *dname, int len)
+{
+ if (!bdi)
+ goto unknown;
+
+ spin_lock_irq(&bdi->lock);
+ if (!bdi->dev) {
+ spin_unlock_irq(&bdi->lock);
+ goto unknown;
+ }
+
+ strlcpy(dname, dev_name(bdi->dev), len);
+ spin_unlock_irq(&bdi->lock);
+ return dname;
+
+unknown:
+ strlcpy(dname, bdi_unknown_name, len);
+ return NULL;
+}
#endif /* _LINUX_BACKING_DEV_H */
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 62f05f605fb5..aa9ba7dcc2d9 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -859,6 +859,7 @@ static int bdi_init(struct backing_dev_info *bdi)
INIT_LIST_HEAD(&bdi->bdi_list);
INIT_LIST_HEAD(&bdi->wb_list);
init_waitqueue_head(&bdi->wb_waitq);
+ spin_lock_init(&bdi->lock);
ret = cgwb_bdi_init(bdi);
@@ -1007,15 +1008,19 @@ static void bdi_remove_from_list(struct backing_dev_info *bdi)
void bdi_unregister(struct backing_dev_info *bdi)
{
+ struct device *dev = bdi->dev;
+
/* make sure nobody finds us on the bdi_list anymore */
bdi_remove_from_list(bdi);
wb_shutdown(&bdi->wb);
cgwb_bdi_unregister(bdi);
- if (bdi->dev) {
+ if (dev) {
bdi_debug_unregister(bdi);
- device_unregister(bdi->dev);
+ spin_lock_irq(&bdi->lock);
bdi->dev = NULL;
+ spin_unlock_irq(&bdi->lock);
+ device_unregister(dev);
}
if (bdi->owner) {
--
2.17.2
^ permalink raw reply related [flat|nested] 12+ messages in thread* [PATCH v4 3/6] bfq: fix potential kernel crash when print error info
2020-03-25 12:38 [PATCH v4 0/6] bdi: fix use-after-free for bdi device Yufen Yu
2020-03-25 12:38 ` [PATCH v4 1/6] bdi: use bdi_dev_name() to get device name Yufen Yu
2020-03-25 12:38 ` [PATCH v4 2/6] bdi: protect bdi->dev with spinlock Yufen Yu
@ 2020-03-25 12:38 ` Yufen Yu
2020-03-25 12:38 ` [PATCH v4 4/6] memcg: fix crash in wb_workfn when bdi unregister Yufen Yu
` (4 subsequent siblings)
7 siblings, 0 replies; 12+ messages in thread
From: Yufen Yu @ 2020-03-25 12:38 UTC (permalink / raw)
To: axboe, linux-block; +Cc: tj, jack, bvanassche, tytso, gregkh, hch
Replace bdi_dev_name() with bdi_get_dev_name(). Then, we can fix
potential use-after-free or NULL pointer reference for bdi->dev
when bdi unregister.
Signed-off-by: Yufen Yu <yuyufen@huawei.com>
---
block/bfq-iosched.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 94261b7d7181..a8a67a95006e 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -4971,6 +4971,7 @@ bfq_set_next_ioprio_data(struct bfq_queue *bfqq, struct bfq_io_cq *bic)
struct task_struct *tsk = current;
int ioprio_class;
struct bfq_data *bfqd = bfqq->bfqd;
+ char dname[BDI_DEV_NAME_LEN];
if (!bfqd)
return;
@@ -4978,9 +4979,9 @@ bfq_set_next_ioprio_data(struct bfq_queue *bfqq, struct bfq_io_cq *bic)
ioprio_class = IOPRIO_PRIO_CLASS(bic->ioprio);
switch (ioprio_class) {
default:
- pr_err("bdi %s: bfq: bad prio class %d\n",
- bdi_dev_name(bfqq->bfqd->queue->backing_dev_info),
- ioprio_class);
+ bdi_get_dev_name(bfqq->bfqd->queue->backing_dev_info, dname,
+ BDI_DEV_NAME_LEN);
+ pr_err("bdi %s: bfq: bad prio class %d\n", dname, ioprio_class);
/* fall through */
case IOPRIO_CLASS_NONE:
/*
--
2.17.2
^ permalink raw reply related [flat|nested] 12+ messages in thread* [PATCH v4 4/6] memcg: fix crash in wb_workfn when bdi unregister
2020-03-25 12:38 [PATCH v4 0/6] bdi: fix use-after-free for bdi device Yufen Yu
` (2 preceding siblings ...)
2020-03-25 12:38 ` [PATCH v4 3/6] bfq: fix potential kernel crash when print error info Yufen Yu
@ 2020-03-25 12:38 ` Yufen Yu
2020-03-25 12:38 ` [PATCH v4 5/6] blk-wbt: replace bdi_dev_name() with bdi_get_dev_name() Yufen Yu
` (3 subsequent siblings)
7 siblings, 0 replies; 12+ messages in thread
From: Yufen Yu @ 2020-03-25 12:38 UTC (permalink / raw)
To: axboe, linux-block; +Cc: tj, jack, bvanassche, tytso, gregkh, hch
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@huawei.com>
---
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
^ permalink raw reply related [flat|nested] 12+ messages in thread* [PATCH v4 5/6] blk-wbt: replace bdi_dev_name() with bdi_get_dev_name()
2020-03-25 12:38 [PATCH v4 0/6] bdi: fix use-after-free for bdi device Yufen Yu
` (3 preceding siblings ...)
2020-03-25 12:38 ` [PATCH v4 4/6] memcg: fix crash in wb_workfn when bdi unregister Yufen Yu
@ 2020-03-25 12:38 ` Yufen Yu
2020-03-25 12:38 ` [PATCH v4 6/6] blkcg: fix use-after-free for bdi->dev Yufen Yu
` (2 subsequent siblings)
7 siblings, 0 replies; 12+ messages in thread
From: Yufen Yu @ 2020-03-25 12:38 UTC (permalink / raw)
To: axboe, linux-block; +Cc: tj, jack, bvanassche, tytso, gregkh, hch
wb_timer_fn() can be called after bdi unregister. So, we get bdi
device name by bdi_get_dev_name() to avoid use-after-free or null
pointer deference for bdi->dev.
Signed-off-by: Yufen Yu <yuyufen@huawei.com>
---
include/trace/events/wbt.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/include/trace/events/wbt.h b/include/trace/events/wbt.h
index 9996420d7ec4..3fbf15565962 100644
--- a/include/trace/events/wbt.h
+++ b/include/trace/events/wbt.h
@@ -33,7 +33,7 @@ TRACE_EVENT(wbt_stat,
),
TP_fast_assign(
- strlcpy(__entry->name, bdi_dev_name(bdi),
+ bdi_get_dev_name(bdi, __entry->name,
ARRAY_SIZE(__entry->name));
__entry->rmean = stat[0].mean;
__entry->rmin = stat[0].min;
@@ -68,7 +68,7 @@ TRACE_EVENT(wbt_lat,
),
TP_fast_assign(
- strlcpy(__entry->name, bdi_dev_name(bdi),
+ bdi_get_dev_name(bdi, __entry->name,
ARRAY_SIZE(__entry->name));
__entry->lat = div_u64(lat, 1000);
),
@@ -105,7 +105,7 @@ TRACE_EVENT(wbt_step,
),
TP_fast_assign(
- strlcpy(__entry->name, bdi_dev_name(bdi),
+ bdi_get_dev_name(bdi, __entry->name,
ARRAY_SIZE(__entry->name));
__entry->msg = msg;
__entry->step = step;
@@ -141,7 +141,7 @@ TRACE_EVENT(wbt_timer,
),
TP_fast_assign(
- strlcpy(__entry->name, bdi_dev_name(bdi),
+ bdi_get_dev_name(bdi, __entry->name,
ARRAY_SIZE(__entry->name));
__entry->status = status;
__entry->step = step;
--
2.17.2
^ permalink raw reply related [flat|nested] 12+ messages in thread* [PATCH v4 6/6] blkcg: fix use-after-free for bdi->dev
2020-03-25 12:38 [PATCH v4 0/6] bdi: fix use-after-free for bdi device Yufen Yu
` (4 preceding siblings ...)
2020-03-25 12:38 ` [PATCH v4 5/6] blk-wbt: replace bdi_dev_name() with bdi_get_dev_name() Yufen Yu
@ 2020-03-25 12:38 ` Yufen Yu
2020-04-09 13:28 ` [PATCH v4 0/6] bdi: fix use-after-free for bdi device Yufen Yu
2020-04-14 15:52 ` Christoph Hellwig
7 siblings, 0 replies; 12+ messages in thread
From: Yufen Yu @ 2020-03-25 12:38 UTC (permalink / raw)
To: axboe, linux-block; +Cc: tj, jack, bvanassche, tytso, gregkh, hch
__blkg_prfill_rwstat() tries to get the device name by 'bdi->dev',
while the device and kobj->name has been freed by bdi_unregister().
Then, blkg_dev_name() will return an invalid name pointer, resulting
in crash on string(). The race as following:
CPU1 CPU2
blkg_print_stat_bytes
__scsi_remove_device
del_gendisk
bdi_unregister
put_device(bdi->dev)
kfree(bdi->dev)
__blkg_prfill_rwstat
blkg_dev_name
//use the freed bdi->dev
dev_name(blkg->q->backing_dev_info->dev)
bdi->dev = NULL
After protecing "bdi->dev" with lock, we just need to use
bdi_get_dev_name() to get device name. Then, the race can be fixed.
Signed-off-by: Yufen Yu <yuyufen@huawei.com>
---
block/blk-cgroup-rwstat.c | 6 ++++--
block/blk-cgroup.c | 19 ++++++-------------
block/blk-iocost.c | 14 ++++++++------
block/blk-iolatency.c | 5 +++--
block/blk-throttle.c | 6 ++++--
include/linux/blk-cgroup.h | 1 -
6 files changed, 25 insertions(+), 26 deletions(-)
diff --git a/block/blk-cgroup-rwstat.c b/block/blk-cgroup-rwstat.c
index 85d5790ac49b..2dc260802228 100644
--- a/block/blk-cgroup-rwstat.c
+++ b/block/blk-cgroup-rwstat.c
@@ -4,6 +4,7 @@
* Do not use in new code.
*/
#include "blk-cgroup-rwstat.h"
+#include <linux/backing-dev.h>
int blkg_rwstat_init(struct blkg_rwstat *rwstat, gfp_t gfp)
{
@@ -49,11 +50,12 @@ u64 __blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
[BLKG_RWSTAT_ASYNC] = "Async",
[BLKG_RWSTAT_DISCARD] = "Discard",
};
- const char *dname = blkg_dev_name(pd->blkg);
+ char dname[BDI_DEV_NAME_LEN];
u64 v;
int i;
- if (!dname)
+ if (!bdi_get_dev_name(pd->blkg->q->backing_dev_info, dname,
+ BDI_DEV_NAME_LEN))
return 0;
for (i = 0; i < BLKG_RWSTAT_NR; i++)
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index be92405c6547..a072ca6141ca 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -492,14 +492,6 @@ static int blkcg_reset_stats(struct cgroup_subsys_state *css,
return 0;
}
-const char *blkg_dev_name(struct blkcg_gq *blkg)
-{
- /* some drivers (floppy) instantiate a queue w/o disk registered */
- if (blkg->q->backing_dev_info->dev)
- return bdi_dev_name(blkg->q->backing_dev_info);
- return NULL;
-}
-
/**
* blkcg_print_blkgs - helper for printing per-blkg data
* @sf: seq_file to print to
@@ -551,9 +543,10 @@ EXPORT_SYMBOL_GPL(blkcg_print_blkgs);
*/
u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v)
{
- const char *dname = blkg_dev_name(pd->blkg);
+ char dname[BDI_DEV_NAME_LEN];
- if (!dname)
+ if (!bdi_get_dev_name(pd->blkg->q->backing_dev_info, dname,
+ BDI_DEV_NAME_LEN))
return 0;
seq_printf(sf, "%s %llu\n", dname, (unsigned long long)v);
@@ -749,7 +742,7 @@ static int blkcg_print_stat(struct seq_file *sf, void *v)
hlist_for_each_entry_rcu(blkg, &blkcg->blkg_list, blkcg_node) {
struct blkg_iostat_set *bis = &blkg->iostat;
- const char *dname;
+ char dname[BDI_DEV_NAME_LEN];
char *buf;
u64 rbytes, wbytes, rios, wios, dbytes, dios;
size_t size = seq_get_buf(sf, &buf), off = 0;
@@ -762,8 +755,8 @@ static int blkcg_print_stat(struct seq_file *sf, void *v)
if (!blkg->online)
goto skip;
- dname = blkg_dev_name(blkg);
- if (!dname)
+ if (!bdi_get_dev_name(blkg->q->backing_dev_info, dname,
+ BDI_DEV_NAME_LEN))
goto skip;
/*
diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 9a599cc28c29..2ae69d475d60 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -2047,10 +2047,11 @@ static void ioc_pd_free(struct blkg_policy_data *pd)
static u64 ioc_weight_prfill(struct seq_file *sf, struct blkg_policy_data *pd,
int off)
{
- const char *dname = blkg_dev_name(pd->blkg);
+ char dname[BDI_DEV_NAME_LEN];
struct ioc_gq *iocg = pd_to_iocg(pd);
- if (dname && iocg->cfg_weight)
+ if (bdi_get_dev_name(pd->blkg, dname, BDI_DEV_NAME_LEN) &&
+ iocg->cfg_weight)
seq_printf(sf, "%s %u\n", dname, iocg->cfg_weight);
return 0;
}
@@ -2133,10 +2134,11 @@ static ssize_t ioc_weight_write(struct kernfs_open_file *of, char *buf,
static u64 ioc_qos_prfill(struct seq_file *sf, struct blkg_policy_data *pd,
int off)
{
- const char *dname = blkg_dev_name(pd->blkg);
+ char dname[BDI_DEV_NAME_LEN];
struct ioc *ioc = pd_to_iocg(pd)->ioc;
- if (!dname)
+ if (!bdi_get_dev_name(pd->blkg->q->backing_dev_info, dname,
+ BDI_DEV_NAME_LEN))
return 0;
seq_printf(sf, "%s enable=%d ctrl=%s rpct=%u.%02u rlat=%u wpct=%u.%02u wlat=%u min=%u.%02u max=%u.%02u\n",
@@ -2304,11 +2306,11 @@ static ssize_t ioc_qos_write(struct kernfs_open_file *of, char *input,
static u64 ioc_cost_model_prfill(struct seq_file *sf,
struct blkg_policy_data *pd, int off)
{
- const char *dname = blkg_dev_name(pd->blkg);
+ char dname[BDI_DEV_NAME_LEN];
struct ioc *ioc = pd_to_iocg(pd)->ioc;
u64 *u = ioc->params.i_lcoefs;
- if (!dname)
+ if (!bdi_get_dev_name(pd->blkg, dname, BDI_DEV_NAME_LEN))
return 0;
seq_printf(sf, "%s ctrl=%s model=linear "
diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c
index c128d50cb410..2ab49167aea1 100644
--- a/block/blk-iolatency.c
+++ b/block/blk-iolatency.c
@@ -868,9 +868,10 @@ static u64 iolatency_prfill_limit(struct seq_file *sf,
struct blkg_policy_data *pd, int off)
{
struct iolatency_grp *iolat = pd_to_lat(pd);
- const char *dname = blkg_dev_name(pd->blkg);
+ char dname[BDI_DEV_NAME_LEN];
- if (!dname || !iolat->min_lat_nsec)
+ if (!bdi_get_dev_name(pd->blkg, dname, BDI_DEV_NAME_LEN)
+ || !iolat->min_lat_nsec)
return 0;
seq_printf(sf, "%s target=%llu\n",
dname, div_u64(iolat->min_lat_nsec, NSEC_PER_USEC));
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 98233c9c65a8..f77dc93d4e83 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -13,6 +13,7 @@
#include <linux/blk-cgroup.h>
#include "blk.h"
#include "blk-cgroup-rwstat.h"
+#include <linux/backing-dev.h>
/* Max dispatch from a group in 1 round */
static int throtl_grp_quantum = 8;
@@ -1560,14 +1561,15 @@ static u64 tg_prfill_limit(struct seq_file *sf, struct blkg_policy_data *pd,
int off)
{
struct throtl_grp *tg = pd_to_tg(pd);
- const char *dname = blkg_dev_name(pd->blkg);
+ char dname[BDI_DEV_NAME_LEN];
char bufs[4][21] = { "max", "max", "max", "max" };
u64 bps_dft;
unsigned int iops_dft;
char idle_time[26] = "";
char latency_time[26] = "";
- if (!dname)
+ if (!bdi_get_dev_name(pd->blkg->q->backing_dev_info, dname,
+ BDI_DEV_NAME_LEN))
return 0;
if (off == LIMIT_LOW) {
diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index e4a6949fd171..384b3343d5f4 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -198,7 +198,6 @@ int blkcg_activate_policy(struct request_queue *q,
void blkcg_deactivate_policy(struct request_queue *q,
const struct blkcg_policy *pol);
-const char *blkg_dev_name(struct blkcg_gq *blkg);
void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
u64 (*prfill)(struct seq_file *,
struct blkg_policy_data *, int),
--
2.17.2
^ permalink raw reply related [flat|nested] 12+ messages in thread* Re: [PATCH v4 0/6] bdi: fix use-after-free for bdi device
2020-03-25 12:38 [PATCH v4 0/6] bdi: fix use-after-free for bdi device Yufen Yu
` (5 preceding siblings ...)
2020-03-25 12:38 ` [PATCH v4 6/6] blkcg: fix use-after-free for bdi->dev Yufen Yu
@ 2020-04-09 13:28 ` Yufen Yu
2020-04-14 14:44 ` Theodore Y. Ts'o
2020-04-14 15:52 ` Christoph Hellwig
7 siblings, 1 reply; 12+ messages in thread
From: Yufen Yu @ 2020-04-09 13:28 UTC (permalink / raw)
To: axboe, linux-block; +Cc: tj, jack, bvanassche, tytso, gregkh, hch
ping
On 2020/3/25 20:38, Yufen Yu wrote:
> Hi, all
>
> We have reported a use-after-free crash for bdi device in __blkg_prfill_rwstat().
> The bug is caused by printing device kobj->name while the device and kobj->name
> has been freed by bdi_unregister().
>
> In fact, commit 68f23b8906 "memcg: fix a crash in wb_workfn when a device disappears"
> has tried to address the issue, but the code is till somewhat racy after that commit.
>
> In this patchset, we try to protect bdi->dev with spinlock and copy device name
> into caller buffer, avoiding use-after-free.
>
> V4:
> * Fix coding error in bdi_get_dev_name()
> * Write one patch for each broken caller
>
> V3:
> https://www.spinics.net/lists/linux-block/msg51111.html
> Use spinlock to protect bdi->dev and copy device name into caller buffer
>
> V2:
> https://www.spinics.net/lists/linux-fsdevel/msg163206.html
> Try to protect device lifetime with RCU.
>
> V1:
> https://www.spinics.net/lists/linux-block/msg49693.html
> Add a new spinlock and copy kobj->name into caller buffer.
> Or using synchronize_rcu() to wait until reader complete.
>
> Yufen Yu (6):
> bdi: use bdi_dev_name() to get device name
> bdi: protect bdi->dev with spinlock
> bfq: fix potential kernel crash when print error info
> memcg: fix crash in wb_workfn when bdi unregister
> blk-wbt: replace bdi_dev_name() with bdi_get_dev_name()
> blkcg: fix use-after-free for bdi->dev
>
> block/bfq-iosched.c | 6 +++--
> block/blk-cgroup-rwstat.c | 6 +++--
> block/blk-cgroup.c | 19 +++++-----------
> block/blk-iocost.c | 14 +++++++-----
> block/blk-iolatency.c | 5 +++--
> block/blk-throttle.c | 6 +++--
> fs/ceph/debugfs.c | 2 +-
> fs/fs-writeback.c | 4 +++-
> include/linux/backing-dev-defs.h | 1 +
> include/linux/backing-dev.h | 26 ++++++++++++++++++++++
> include/linux/blk-cgroup.h | 1 -
> include/trace/events/wbt.h | 8 +++----
> include/trace/events/writeback.h | 38 ++++++++++++++------------------
> mm/backing-dev.c | 9 ++++++--
> 14 files changed, 88 insertions(+), 57 deletions(-)
>
^ permalink raw reply [flat|nested] 12+ messages in thread* Re: [PATCH v4 0/6] bdi: fix use-after-free for bdi device
2020-04-09 13:28 ` [PATCH v4 0/6] bdi: fix use-after-free for bdi device Yufen Yu
@ 2020-04-14 14:44 ` Theodore Y. Ts'o
0 siblings, 0 replies; 12+ messages in thread
From: Theodore Y. Ts'o @ 2020-04-14 14:44 UTC (permalink / raw)
To: Yufen Yu; +Cc: axboe, linux-block, tj, jack, bvanassche, gregkh, hch
On Thu, Apr 09, 2020 at 09:28:07PM +0800, Yufen Yu wrote:
> ping
ping**2
Can this go in as a bugfix during this cycle?
- Ted
>
> On 2020/3/25 20:38, Yufen Yu wrote:
> > Hi, all
> >
> > We have reported a use-after-free crash for bdi device in __blkg_prfill_rwstat().
> > The bug is caused by printing device kobj->name while the device and kobj->name
> > has been freed by bdi_unregister().
> >
> > In fact, commit 68f23b8906 "memcg: fix a crash in wb_workfn when a device disappears"
> > has tried to address the issue, but the code is till somewhat racy after that commit.
> >
> > In this patchset, we try to protect bdi->dev with spinlock and copy device name
> > into caller buffer, avoiding use-after-free.
> >
> > V4:
> > * Fix coding error in bdi_get_dev_name()
> > * Write one patch for each broken caller
> >
> > V3:
> > https://www.spinics.net/lists/linux-block/msg51111.html
> > Use spinlock to protect bdi->dev and copy device name into caller buffer
> >
> > V2:
> > https://www.spinics.net/lists/linux-fsdevel/msg163206.html
> > Try to protect device lifetime with RCU.
> >
> > V1:
> > https://www.spinics.net/lists/linux-block/msg49693.html
> > Add a new spinlock and copy kobj->name into caller buffer.
> > Or using synchronize_rcu() to wait until reader complete.
> >
> > Yufen Yu (6):
> > bdi: use bdi_dev_name() to get device name
> > bdi: protect bdi->dev with spinlock
> > bfq: fix potential kernel crash when print error info
> > memcg: fix crash in wb_workfn when bdi unregister
> > blk-wbt: replace bdi_dev_name() with bdi_get_dev_name()
> > blkcg: fix use-after-free for bdi->dev
> >
> > block/bfq-iosched.c | 6 +++--
> > block/blk-cgroup-rwstat.c | 6 +++--
> > block/blk-cgroup.c | 19 +++++-----------
> > block/blk-iocost.c | 14 +++++++-----
> > block/blk-iolatency.c | 5 +++--
> > block/blk-throttle.c | 6 +++--
> > fs/ceph/debugfs.c | 2 +-
> > fs/fs-writeback.c | 4 +++-
> > include/linux/backing-dev-defs.h | 1 +
> > include/linux/backing-dev.h | 26 ++++++++++++++++++++++
> > include/linux/blk-cgroup.h | 1 -
> > include/trace/events/wbt.h | 8 +++----
> > include/trace/events/writeback.h | 38 ++++++++++++++------------------
> > mm/backing-dev.c | 9 ++++++--
> > 14 files changed, 88 insertions(+), 57 deletions(-)
> >
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH v4 0/6] bdi: fix use-after-free for bdi device
2020-03-25 12:38 [PATCH v4 0/6] bdi: fix use-after-free for bdi device Yufen Yu
` (6 preceding siblings ...)
2020-04-09 13:28 ` [PATCH v4 0/6] bdi: fix use-after-free for bdi device Yufen Yu
@ 2020-04-14 15:52 ` Christoph Hellwig
2020-04-15 9:34 ` Jan Kara
7 siblings, 1 reply; 12+ messages in thread
From: Christoph Hellwig @ 2020-04-14 15:52 UTC (permalink / raw)
To: Yufen Yu; +Cc: axboe, linux-block, tj, jack, bvanassche, tytso, gregkh, hch
Looking through this series the whoe approach of using a lock to clear
the ->dev pointer looks rather odd to me. What is the reason for now
simply adding a separately allocated name field to struct
backing_dev_info that the name is copied to on allocation, and then
the ->dev field is not relevant for name printing and we don't need
to copy out the name in the potentionally more fast path callers that
want to print it?
^ permalink raw reply [flat|nested] 12+ messages in thread* Re: [PATCH v4 0/6] bdi: fix use-after-free for bdi device
2020-04-14 15:52 ` Christoph Hellwig
@ 2020-04-15 9:34 ` Jan Kara
2020-04-16 5:36 ` Christoph Hellwig
0 siblings, 1 reply; 12+ messages in thread
From: Jan Kara @ 2020-04-15 9:34 UTC (permalink / raw)
To: Christoph Hellwig
Cc: Yufen Yu, axboe, linux-block, tj, jack, bvanassche, tytso, gregkh
On Tue 14-04-20 08:52:28, Christoph Hellwig wrote:
> Looking through this series the whoe approach of using a lock to clear
> the ->dev pointer looks rather odd to me. What is the reason for now
> simply adding a separately allocated name field to struct
> backing_dev_info that the name is copied to on allocation, and then
> the ->dev field is not relevant for name printing and we don't need
> to copy out the name in the potentionally more fast path callers that
> want to print it?
Yeah, that's what I was suggesting as well [1] - especially since we
already have bdi->name with a dubious value (but looking into it now, we
would need a separate dev_name field since bdi->name is visible in sysfs so
we cannot change that). But Yufen explained to me that this could result in
bogus name being reported when bdi gets re-registered. Not sure if that's
serious enough but it could happen...
Honza
[1] https://lore.kernel.org/linux-block/20200219125505.GP16121@quack2.suse.cz
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH v4 0/6] bdi: fix use-after-free for bdi device
2020-04-15 9:34 ` Jan Kara
@ 2020-04-16 5:36 ` Christoph Hellwig
0 siblings, 0 replies; 12+ messages in thread
From: Christoph Hellwig @ 2020-04-16 5:36 UTC (permalink / raw)
To: Jan Kara
Cc: Christoph Hellwig, Yufen Yu, axboe, linux-block, tj, bvanassche,
tytso, gregkh
On Wed, Apr 15, 2020 at 11:34:59AM +0200, Jan Kara wrote:
> Yeah, that's what I was suggesting as well [1] - especially since we
> already have bdi->name with a dubious value (but looking into it now, we
> would need a separate dev_name field since bdi->name is visible in sysfs so
> we cannot change that).
That is a little anoying, but not the end of the world.
> But Yufen explained to me that this could result in
> bogus name being reported when bdi gets re-registered. Not sure if that's
> serious enough but it could happen...
I don't think that is a problem at all. If it is a problem we can just
replace the ->dev_name pointer with one that says "(unregistered)" at
unregister time, but to me that seems worse than just keeping the name
around.
^ permalink raw reply [flat|nested] 12+ messages in thread