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Subject[PATCH] crypto: ccp: add check to get PSP master only when PSP is detected
Date
Paulian reported the below kernel crash on Ryzen 5 system:

BUG: unable to handle kernel NULL pointer dereference at 0000000000000073
RIP: 0010:.LC0+0x41f/0xa00
RSP: 0018:ffffa9968003bdd0 EFLAGS: 00010002
RAX: ffffffffb113b130 RBX: 0000000000000000 RCX: 00000000000005a7
RDX: 00000000000000ff RSI: ffff8b46dee651a0 RDI: ffffffffb1bd617c
RBP: 0000000000000246 R08: 00000000000251a0 R09: 0000000000000000
R10: ffffd81f11a38200 R11: ffff8b52e8e0a161 R12: ffffffffb19db220
R13: 0000000000000007 R14: ffffffffb17e4888 R15: 5dccd7affc30a31e
FS: 0000000000000000(0000) GS:ffff8b46dee40000(0000) knlGS:0000000000000000
CR2: 0000000000000073 CR3: 000080128120a000 CR4: 00000000003406e0
Call Trace:
? sp_get_psp_master_device+0x56/0x80
? map_properties+0x540/0x540
? psp_pci_init+0x20/0xe0
? map_properties+0x540/0x540
? sp_mod_init+0x16/0x1a
? do_one_initcall+0x4b/0x190
? kernel_init_freeable+0x19b/0x23c
? rest_init+0xb0/0xb0
? kernel_init+0xa/0x100
? ret_from_fork+0x22/0x40

Since Ryzen does not support PSP/SEV firmware hence i->psp_data will
NULL in all sp instances. In those cases, 'i' will point to the
list head after list_for_each_entry(). Dereferencing the head will
cause kernel crash.

Add check to call get master device only when PSP/SEV is detected.

Reported-by: Paulian Bogdan Marinca <paulian@marinca.net>
Cc: Borislav Petkov <bp@suse.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
CC: Gary R Hook <gary.hook@amd.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
drivers/crypto/ccp/psp-dev.c | 1 +
drivers/crypto/ccp/sp-dev.c | 6 +++---
2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/crypto/ccp/psp-dev.c b/drivers/crypto/ccp/psp-dev.c
index b3afb6cc9d72..b342210e582a 100644
--- a/drivers/crypto/ccp/psp-dev.c
+++ b/drivers/crypto/ccp/psp-dev.c
@@ -677,6 +677,7 @@ static int sev_misc_init(struct psp_device *psp)

static int sev_init(struct psp_device *psp)
{
+ return 1;
/* Check if device supports SEV feature */
if (!(ioread32(psp->io_regs + PSP_FEATURE_REG) & 1)) {
dev_dbg(psp->dev, "device does not support SEV\n");
diff --git a/drivers/crypto/ccp/sp-dev.c b/drivers/crypto/ccp/sp-dev.c
index eb0da6572720..e0459002eb71 100644
--- a/drivers/crypto/ccp/sp-dev.c
+++ b/drivers/crypto/ccp/sp-dev.c
@@ -252,12 +252,12 @@ struct sp_device *sp_get_psp_master_device(void)
goto unlock;

list_for_each_entry(i, &sp_units, entry) {
- if (i->psp_data)
+ if (i->psp_data && i->get_psp_master_device) {
+ ret = i->get_psp_master_device();
break;
+ }
}

- if (i->get_psp_master_device)
- ret = i->get_psp_master_device();
unlock:
write_unlock_irqrestore(&sp_unit_lock, flags);
return ret;
--
2.14.3
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