From 211f514ebf1ef5de37b1cf6df9d28a56cfd242ca Mon Sep 17 00:00:00 2001 From: Rick Edgecombe Date: Mon, 11 Mar 2024 09:15:55 -0700 Subject: Drivers: hv: vmbus: Track decrypted status in vmbus_gpadl In CoCo VMs it is possible for the untrusted host to cause set_memory_encrypted() or set_memory_decrypted() to fail such that an error is returned and the resulting memory is shared. Callers need to take care to handle these errors to avoid returning decrypted (shared) memory to the page allocator, which could lead to functional or security issues. In order to make sure callers of vmbus_establish_gpadl() and vmbus_teardown_gpadl() don't return decrypted/shared pages to allocators, add a field in struct vmbus_gpadl to keep track of the decryption status of the buffers. This will allow the callers to know if they should free or leak the pages. Signed-off-by: Rick Edgecombe Signed-off-by: Michael Kelley Reviewed-by: Kuppuswamy Sathyanarayanan Acked-by: Kirill A. Shutemov Link: https://lore.kernel.org/r/20240311161558.1310-3-mhklinux@outlook.com Signed-off-by: Wei Liu Message-ID: <20240311161558.1310-3-mhklinux@outlook.com> --- drivers/hv/channel.c | 25 +++++++++++++++++++++---- include/linux/hyperv.h | 1 + 2 files changed, 22 insertions(+), 4 deletions(-) diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c index adbf674355b2b..98259b4925029 100644 --- a/drivers/hv/channel.c +++ b/drivers/hv/channel.c @@ -436,9 +436,18 @@ static int __vmbus_establish_gpadl(struct vmbus_channel *channel, (atomic_inc_return(&vmbus_connection.next_gpadl_handle) - 1); ret = create_gpadl_header(type, kbuffer, size, send_offset, &msginfo); - if (ret) + if (ret) { + gpadl->decrypted = false; return ret; + } + /* + * Set the "decrypted" flag to true for the set_memory_decrypted() + * success case. In the failure case, the encryption state of the + * memory is unknown. Leave "decrypted" as true to ensure the + * memory will be leaked instead of going back on the free list. + */ + gpadl->decrypted = true; ret = set_memory_decrypted((unsigned long)kbuffer, PFN_UP(size)); if (ret) { @@ -527,9 +536,15 @@ cleanup: kfree(msginfo); - if (ret) - set_memory_encrypted((unsigned long)kbuffer, - PFN_UP(size)); + if (ret) { + /* + * If set_memory_encrypted() fails, the decrypted flag is + * left as true so the memory is leaked instead of being + * put back on the free list. + */ + if (!set_memory_encrypted((unsigned long)kbuffer, PFN_UP(size))) + gpadl->decrypted = false; + } return ret; } @@ -850,6 +865,8 @@ post_msg_err: if (ret) pr_warn("Fail to set mem host visibility in GPADL teardown %d.\n", ret); + gpadl->decrypted = ret; + return ret; } EXPORT_SYMBOL_GPL(vmbus_teardown_gpadl); diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h index 6ef0557b4bff8..96ceb4095425e 100644 --- a/include/linux/hyperv.h +++ b/include/linux/hyperv.h @@ -832,6 +832,7 @@ struct vmbus_gpadl { u32 gpadl_handle; u32 size; void *buffer; + bool decrypted; }; struct vmbus_channel { -- cgit 1.2.3-korg