[PATCH] block: ensure the bdi is freed after inode_detach_wb
From: Christoph Hellwig <hch@lst.de>
Date: 2021-08-12 07:34:45
Subsystem:
block layer, filesystems (vfs and infrastructure), the rest · Maintainers:
Jens Axboe, Alexander Viro, Christian Brauner, Linus Torvalds
inode_detach_wb references the "main" bdi of the inode. With the
recent change to move the bdi from the request_queue to the gendisk
this causes a guaranteed use after free when using certain cgroup
configurations. The big itself is older through as any non-default
inode reference (e.g. an open file descriptor) could have injected
this use after free even before that.
Fixes: 52ebea749aae ("writeback: make backing_dev_info host cgroup-specific bdi_writebacks")
Reported-by: Qian Cai <redacted>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Qian Cai <redacted>
---
block/genhd.c | 1 -
fs/block_dev.c | 5 ++++-
2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/block/genhd.c b/block/genhd.c
index 9e60722e9ce7..3c1ca21ab2ee 100644
--- a/block/genhd.c
+++ b/block/genhd.c@@ -1051,7 +1051,6 @@ static void disk_release(struct device *dev) might_sleep(); - bdi_put(disk->bdi); if (MAJOR(dev->devt) == BLOCK_EXT_MAJOR) blk_free_ext_minor(MINOR(dev->devt)); disk_release_events(disk);
diff --git a/fs/block_dev.c b/fs/block_dev.c
index a2c3d11eda5e..a61273ff1dcf 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c@@ -826,11 +826,14 @@ static void init_once(void *data) static void bdev_evict_inode(struct inode *inode) { + struct block_device *bdev = I_BDEV(inode); + truncate_inode_pages_final(&inode->i_data); invalidate_inode_buffers(inode); /* is it needed here? */ clear_inode(inode); - /* Detach inode from wb early as bdi_put() may free bdi->wb */ inode_detach_wb(inode); + if (!bdev_is_partition(bdev)) + bdi_put(bdev->bd_disk->bdi); } static const struct super_operations bdev_sops = {
--
2.30.2