Re: [PATCH v1 1/5] crypto: ccp: Fix command completion detection race

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On 07/03/2018 12:11 PM, Tom Lendacky wrote:
The wait_event() function is used to detect command completion.  The
interrupt handler will set the wait condition variable when the interrupt
is triggered.  However, the variable used for wait_event() is initialized
after the command has been submitted, which can create a race condition
with the interrupt handler and result in the wait_event() never returning.
Move the initialization of the wait condition variable to just before
command submission.

Fixes: 200664d5237f ("crypto: ccp: Add Secure Encrypted Virtualization (SEV) command support")
Cc: <stable@xxxxxxxxxxxxxxx> # 4.16.x-
Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>

Acked-by: Gary R Hook <gary.hook@xxxxxxx>

---
  drivers/crypto/ccp/psp-dev.c |    4 ++--
  1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/crypto/ccp/psp-dev.c b/drivers/crypto/ccp/psp-dev.c
index ff478d8..973d683 100644
--- a/drivers/crypto/ccp/psp-dev.c
+++ b/drivers/crypto/ccp/psp-dev.c
@@ -84,8 +84,6 @@ static irqreturn_t psp_irq_handler(int irq, void *data)
static void sev_wait_cmd_ioc(struct psp_device *psp, unsigned int *reg)
  {
-	psp->sev_int_rcvd = 0;
-
  	wait_event(psp->sev_int_queue, psp->sev_int_rcvd);
  	*reg = ioread32(psp->io_regs + PSP_CMDRESP);
  }
@@ -148,6 +146,8 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
  	iowrite32(phys_lsb, psp->io_regs + PSP_CMDBUFF_ADDR_LO);
  	iowrite32(phys_msb, psp->io_regs + PSP_CMDBUFF_ADDR_HI);
+ psp->sev_int_rcvd = 0;
+
  	reg = cmd;
  	reg <<= PSP_CMDRESP_CMD_SHIFT;
  	reg |= PSP_CMDRESP_IOC;





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