btrfs: Check read-only status of roots during send
All the subvolues that are involved in send must be read-only during the
whole operation. The ioctl SUBVOL_SETFLAGS could be used to change the
status to read-write and the result of send stream is undefined if the
data change unexpectedly.
Fix that by adding a refcount for all involved roots and verify that
there's no send in progress during SUBVOL_SETFLAGS ioctl call that does
read-only -> read-write transition.
We need refcounts because there are no restrictions on number of send
parallel operations currently run on a single subvolume, be it source,
parent or one of the multiple clone sources.
Kernel is silent when the RO checks fail and returns EPERM. The same set
of checks is done already in userspace before send starts.
Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 3c9053a1..9318c75 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1814,6 +1814,12 @@
struct list_head ordered_extents;
struct list_head ordered_root;
u64 nr_ordered_extents;
+
+ /*
+ * Number of currently running SEND ioctls to prevent
+ * manipulation with the read-only status via SUBVOL_SETFLAGS
+ */
+ int send_in_progress;
};
struct btrfs_ioctl_defrag_range_args {
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 89c2f61..c0dc054 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1706,12 +1706,28 @@
goto out_drop_sem;
root_flags = btrfs_root_flags(&root->root_item);
- if (flags & BTRFS_SUBVOL_RDONLY)
+ if (flags & BTRFS_SUBVOL_RDONLY) {
btrfs_set_root_flags(&root->root_item,
root_flags | BTRFS_ROOT_SUBVOL_RDONLY);
- else
- btrfs_set_root_flags(&root->root_item,
+ } else {
+ /*
+ * Block RO -> RW transition if this subvolume is involved in
+ * send
+ */
+ spin_lock(&root->root_item_lock);
+ if (root->send_in_progress == 0) {
+ btrfs_set_root_flags(&root->root_item,
root_flags & ~BTRFS_ROOT_SUBVOL_RDONLY);
+ spin_unlock(&root->root_item_lock);
+ } else {
+ spin_unlock(&root->root_item_lock);
+ btrfs_warn(root->fs_info,
+ "Attempt to set subvolume %llu read-write during send",
+ root->root_key.objectid);
+ ret = -EPERM;
+ goto out_drop_sem;
+ }
+ }
trans = btrfs_start_transaction(root, 1);
if (IS_ERR(trans)) {
diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index e98c9bc..572e8c7 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -4769,6 +4769,7 @@
struct send_ctx *sctx = NULL;
u32 i;
u64 *clone_sources_tmp = NULL;
+ int clone_sources_to_rollback = 0;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
@@ -4777,6 +4778,14 @@
fs_info = send_root->fs_info;
/*
+ * The subvolume must remain read-only during send, protect against
+ * making it RW.
+ */
+ spin_lock(&send_root->root_item_lock);
+ send_root->send_in_progress++;
+ spin_unlock(&send_root->root_item_lock);
+
+ /*
* This is done when we lookup the root, it should already be complete
* by the time we get here.
*/
@@ -4811,6 +4820,15 @@
up_read(&send_root->fs_info->extent_commit_sem);
}
+ /*
+ * Userspace tools do the checks and warn the user if it's
+ * not RO.
+ */
+ if (!btrfs_root_readonly(send_root)) {
+ ret = -EPERM;
+ goto out;
+ }
+
arg = memdup_user(arg_, sizeof(*arg));
if (IS_ERR(arg)) {
ret = PTR_ERR(arg);
@@ -4897,6 +4915,15 @@
ret = PTR_ERR(clone_root);
goto out;
}
+ clone_sources_to_rollback = i + 1;
+ spin_lock(&clone_root->root_item_lock);
+ clone_root->send_in_progress++;
+ if (!btrfs_root_readonly(clone_root)) {
+ spin_unlock(&clone_root->root_item_lock);
+ ret = -EPERM;
+ goto out;
+ }
+ spin_unlock(&clone_root->root_item_lock);
sctx->clone_roots[i].root = clone_root;
}
vfree(clone_sources_tmp);
@@ -4912,6 +4939,14 @@
ret = PTR_ERR(sctx->parent_root);
goto out;
}
+ spin_lock(&sctx->parent_root->root_item_lock);
+ sctx->parent_root->send_in_progress++;
+ if (!btrfs_root_readonly(sctx->parent_root)) {
+ spin_unlock(&sctx->parent_root->root_item_lock);
+ ret = -EPERM;
+ goto out;
+ }
+ spin_unlock(&sctx->parent_root->root_item_lock);
}
/*
@@ -4940,6 +4975,25 @@
}
out:
+ for (i = 0; sctx && i < clone_sources_to_rollback; i++) {
+ struct btrfs_root *r = sctx->clone_roots[i].root;
+
+ spin_lock(&r->root_item_lock);
+ r->send_in_progress--;
+ spin_unlock(&r->root_item_lock);
+ }
+ if (sctx && !IS_ERR_OR_NULL(sctx->parent_root)) {
+ struct btrfs_root *r = sctx->parent_root;
+
+ spin_lock(&r->root_item_lock);
+ r->send_in_progress--;
+ spin_unlock(&r->root_item_lock);
+ }
+
+ spin_lock(&send_root->root_item_lock);
+ send_root->send_in_progress--;
+ spin_unlock(&send_root->root_item_lock);
+
kfree(arg);
vfree(clone_sources_tmp);