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| author | Jens Axboe <jens.axboe@oracle.com> | 2009-10-29 11:46:12 +0100 |
|---|---|---|
| committer | Jens Axboe <jens.axboe@oracle.com> | 2009-10-29 11:46:12 +0100 |
| commit | 592b09a42fc3ae6737a0f3ecf4fee42ecd0296f8 (patch) | |
| tree | d06ca7165c5dfc5224910993b36a50e54a896831 /mm/backing-dev.c | |
| parent | block: use after free bug in __blkdev_get (diff) | |
| download | linux-592b09a42fc3ae6737a0f3ecf4fee42ecd0296f8.tar.xz linux-592b09a42fc3ae6737a0f3ecf4fee42ecd0296f8.zip | |
backing-dev: ensure that a removed bdi no longer has super_block referencing it
When the bdi is being removed, we have to ensure that no super_blocks
currently have that cached in sb->s_bdi. Normally this is ensured by
the sb having a longer life span than the bdi, but if the device is
suddenly yanked, we have to kill this reference. sb->s_bdi is pointed
to freed memory at that point.
This fixes a problem with sync(1) hanging when a USB stick is pulled
without cleanly umounting it first.
Reported-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'mm/backing-dev.c')
| -rw-r--r-- | mm/backing-dev.c | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/mm/backing-dev.c b/mm/backing-dev.c index 5a37e2055717..1065b715ef64 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -610,6 +610,21 @@ static void bdi_wb_shutdown(struct backing_dev_info *bdi) kthread_stop(wb->task); } +/* + * This bdi is going away now, make sure that no super_blocks point to it + */ +static void bdi_prune_sb(struct backing_dev_info *bdi) +{ + struct super_block *sb; + + spin_lock(&sb_lock); + list_for_each_entry(sb, &super_blocks, s_list) { + if (sb->s_bdi == bdi) + sb->s_bdi = NULL; + } + spin_unlock(&sb_lock); +} + void bdi_unregister(struct backing_dev_info *bdi) { if (bdi->dev) { @@ -682,6 +697,7 @@ void bdi_destroy(struct backing_dev_info *bdi) spin_unlock(&inode_lock); } + bdi_prune_sb(bdi); bdi_unregister(bdi); for (i = 0; i < NR_BDI_STAT_ITEMS; i++) |