btrfs: fix race between quota enable and quota rescan ioctl

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: btrfs: fix race between quota enable and quota rescan ioctl When enabling quotas, at btrfs_quota_enable(), after committing the transaction, we change fs_info->quota_root to point to the quota root we created and set BTRFS_FS_QUOTA_ENABLED at fs_info->flags. Then we try to start the qgroup rescan worker, first by initializing it with a call to qgroup_rescan_init() - however if that fails we end up freeing the quota root but we leave fs_info->quota_root still pointing to it, this can later result in a use-after-free somewhere else. We have previously set the flags BTRFS_FS_QUOTA_ENABLED and BTRFS_QGROUP_STATUS_FLAG_ON, so we can only fail with -EINPROGRESS at btrfs_quota_enable(), which is possible if someone already called the quota rescan ioctl, and therefore started the rescan worker. So fix this by ignoring an -EINPROGRESS and asserting we can't get any other error.

References

• https://git.kernel.org/stable/c/c97f6d528c3f1c83a6b792a8a7928c236c80b8fe
• https://git.kernel.org/stable/c/26b7c0ac49a3eea15559c9d84863736a6d1164b4
• https://git.kernel.org/stable/c/47b5ffe86332af95f0f52be0a63d4da7c2b37b55
• https://git.kernel.org/stable/c/4b996a3014ef014af8f97b60c35f5289210a4720
• https://git.kernel.org/stable/c/0efd9dfc00d677a1d0929319a6103cb2dfc41c22
• https://git.kernel.org/stable/c/6c22f86dd221eba0c7af645b1af73dcbc04ee27b
• https://git.kernel.org/stable/c/331cd9461412e103d07595a10289de90004ac890