On 07/30/2018 10:18 PM, Nikolay Borisov wrote:
On 25.07.2018 16:27, Anand Jain wrote:
test case btrfs/164 reported UAF..
[ 6712.084324] general protection fault: 0000 [#1] PREEMPT SMP
::
[ 6712.195423] btrfs_update_commit_device_size+0x75/0xf0 [btrfs]
[ 6712.201424] btrfs_commit_transaction+0x57d/0xa90 [btrfs]
[ 6712.206999] btrfs_rm_device+0x627/0x850 [btrfs]
[ 6712.211800] btrfs_ioctl+0x2b03/0x3120 [btrfs]
::
reason for this is that btrfs_shrink_device() adds the device resized to
the fs_devices::resized_devices after it has called the last commit
transaction.
So the list fs_devices::resized_devices is not empty when
btrfs_shrink_device() returns.
Now the parent function btrfs_rm_device() calls
btrfs_close_bdev(device);
call_rcu(&device->rcu, free_device_rcu);
and then does the commit transaction.
The commit transaction goes through the fs_devices::resized_devices
in btrfs_update_commit_device_size() and leads to UAF.
Fix this by making sure btrfs_shrink_device() calls the last needed
btrfs_commit_transaction() before the return.
Signed-off-by: Anand Jain <anand.j...@oracle.com>
---
I am bit skeptical about the condition when btrfs_commit_transaction()
fails, can you pls be wary about it when reviewing. Thanks.
Lu/David,
As this issues isn't reproducible at my end, can you pls test this
patch on top of the patch
btrfs: fix missing superblock update in the device delete commit transaction
Thanks.
fs/btrfs/volumes.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 418843b8f8e8..344083cc811c 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -4464,7 +4464,10 @@ int btrfs_shrink_device(struct btrfs_device *device, u64
new_size)
/* Now btrfs_update_device() will change the on-disk size. */
ret = btrfs_update_device(trans, device);
- btrfs_end_transaction(trans);
+ if (ret)
+ btrfs_end_transaction(trans);
Why don't you call btrfs_abort_transaction on error from
btrfs_update_device?
I still can't figure out, any idea why btrfs_abort_transaction?
Per other codes, we are mixing the use of btrfs_abort_transaction and
btrfs_end_transaction for the user initiated threads where
if the thread fails (after btrfs_start_transaction), IMO
we should let the user to try again. But btrfs_abort_transaction
doesn't provide such a choice consistently as it would endup
in RO.
----
static noinline int btrfs_ioctl_resize(struct file *file,
void __user *arg)
{
::
ret = btrfs_grow_device(trans, device, new_size);
btrfs_commit_transaction(trans); <--Bug? ret is not
checked.
----
static int __btrfs_balance(struct btrfs_fs_info *fs_info)
{
::
ret = btrfs_grow_device(trans, device, old_size);
if (ret) {
btrfs_end_transaction(trans);
-----
static noinline int btrfs_ioctl_subvol_setflags(struct file *file,
void __user *arg)
{
::
trans = btrfs_start_transaction(root, 1);
if (IS_ERR(trans)) {
ret = PTR_ERR(trans);
goto out_reset;
}
ret = btrfs_update_root(trans, fs_info->tree_root,
&root->root_key, &root->root_item);
if (ret < 0) {
btrfs_end_transaction(trans);
goto out_reset;
}
ret = btrfs_commit_transaction(trans);
----
static int btrfs_clone(struct inode *src, struct inode *inode,
const u64 off, const u64 olen, const u64
olen_aligned,
const u64 destoff, int no_time_update)
{
trans = btrfs_start_transaction(root, 3);
::
if (ret) {
if (ret != -EOPNOTSUPP)
btrfs_abort_transaction(trans, ret);
btrfs_end_transaction(trans);
goto out;
}
------
::
Thanks, Anand
+ else
+ ret = btrfs_commit_transaction(trans);
done:
btrfs_free_path(path);
if (ret) {
--
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