Commit b250f2f7 authored by Joerg Roedel's avatar Joerg Roedel Committed by Borislav Petkov
Browse files

x86/sev-es: Don't return NULL from sev_es_get_ghcb() 



sev_es_get_ghcb() is called from several places but only one of them
checks the return value. The reaction to returning NULL is always the
same: calling panic() and kill the machine.

Instead of adding checks to all call sites, move the panic() into the
function itself so that it will no longer return NULL.

Fixes: 0786138c ("x86/sev-es: Add a Runtime #VC Exception Handler")
Signed-off-by: default avatarJoerg Roedel <jroedel@suse.de>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Cc: stable@vger.kernel.org # v5.10+
Link: https://lkml.kernel.org/r/20210519135251.30093-2-joro@8bytes.org
parent 0024430e

arch/x86/kernel/sev.c

+12 −13
Original line number Diff line number Diff line
@@ -203,8 +203,18 @@ static __always_inline struct ghcb *sev_es_get_ghcb(struct ghcb_state *state) 
	if (unlikely(data->ghcb_active)) {

		/* GHCB is already in use - save its contents */



		if (unlikely(data->backup_ghcb_active))

			return NULL;

		if (unlikely(data->backup_ghcb_active)) {

			/*

			 * Backup-GHCB is also already in use. There is no way

			 * to continue here so just kill the machine. To make

			 * panic() work, mark GHCBs inactive so that messages

			 * can be printed out.

			 */

			data->ghcb_active        = false;

			data->backup_ghcb_active = false;



			panic("Unable to handle #VC exception! GHCB and Backup GHCB are already in use");

		}



		/* Mark backup_ghcb active before writing to it */

		data->backup_ghcb_active = true;
@@ -1289,7 +1299,6 @@ static __always_inline bool on_vc_fallback_stack(struct pt_regs *regs) 
 */

DEFINE_IDTENTRY_VC_SAFE_STACK(exc_vmm_communication)

{

	struct sev_es_runtime_data *data = this_cpu_read(runtime_data);

	irqentry_state_t irq_state;

	struct ghcb_state state;

	struct es_em_ctxt ctxt;
@@ -1315,16 +1324,6 @@ DEFINE_IDTENTRY_VC_SAFE_STACK(exc_vmm_communication) 
	 */



	ghcb = sev_es_get_ghcb(&state);

	if (!ghcb) {

		/*

		 * Mark GHCBs inactive so that panic() is able to print the

		 * message.

		 */

		data->ghcb_active        = false;

		data->backup_ghcb_active = false;



		panic("Unable to handle #VC exception! GHCB and Backup GHCB are already in use");

	}



	vc_ghcb_invalidate(ghcb);

	result = vc_init_em_ctxt(&ctxt, regs, error_code);