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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: 0786138c78 ("x86/sev-es: Add a Runtime #VC Exception Handler")
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: stable@vger.kernel.org # v5.10+
Link: https://lkml.kernel.org/r/20210519135251.30093-2-joro@8bytes.org
This commit is contained in:
Joerg Roedel 2021-05-19 15:52:44 +02:00 committed by Borislav Petkov
parent 0024430e92
commit b250f2f779
1 changed files with 12 additions and 13 deletions
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25
arch/x86/kernel/sev.c
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@ -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);