[PATCH v2 1/3] Drivers: hv: vmbus: Fix error paths in vmbus_teardown_gpadl()

[Michael Kelley]

In vmbus_teardown_gpadl(), the return value from vmbus_post_msg() is
overwritten by the logic that decides if set_memory_encrypted() should
run. A failure from vmbus_post_msg() is lost and vmbus_teardown_gpadl()
may incorrectly report success. Furthermore, if vmbus_post_msg() fails,
the GPADL remains active on the Hyper-V side, yet in a CoCo VM the
buffer will be re-encrypted anyway.

Fix this by gating buffer re-encryption on success from vmbus_post_msg().
And if either function fails, mark the buffer as decrypted so the memory
will be leaked. The decrypted flag does double-duty: in a CoCo VM it
indicates the decryption status, but at buffer cleanup time in all VMs
it is a "should be leaked due to error" flag.

Reported-by: Sashiko <sashiko-bot@xxxxxxxxxx>
Closes: https://lore.kernel.org/linux-hyperv/20260904160724.82AB51F00A3D@xxxxxxxxxxxxxxx/
Fixes: d4dccf353db8 ("Drivers: hv: vmbus: Mark vmbus ring buffer visible to host in Isolation VM")
Signed-off-by: Michael Kelley <mhklinux@xxxxxxxxxxx>
---
 drivers/hv/channel.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
index f4370617deac..cc86e8505ad0 100644
--- a/drivers/hv/channel.c
+++ b/drivers/hv/channel.c
@@ -1059,14 +1059,14 @@ int vmbus_teardown_gpadl(struct vmbus_channel *channel, struct vmbus_gpadl *gpad
 
 	kfree(info);
 
-	if (gpadl->decrypted)
+	if (!ret && gpadl->decrypted) {
 		ret = set_memory_encrypted((unsigned long)gpadl->buffer,
 					PFN_UP(gpadl->size));
-	else
-		ret = 0;
-	if (ret)
-		pr_warn("Fail to set mem host visibility in GPADL teardown %d.\n", ret);
+		if (ret)
+			pr_warn("Fail to set mem host visibility in GPADL teardown %d.\n", ret);
+	}
 
+	/* If error in ret, mark buffer decrypted so it is leaked */
 	gpadl->decrypted = ret;
 
 	return ret;
-- 
2.25.1