cxl: Fix leaking pid refs in some error paths

In some error paths in functions cxl_start_context and
afu_ioctl_start_work pid references to the current & group-leader tasks
can leak after they are taken. This patch fixes these error paths to
release these pid references before exiting the error path.

Fixes: 7b8ad495d592 ("cxl: Fix DSI misses when the context owning task exits")
Cc: stable@vger.kernel.org # v4.5+
Reviewed-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Reported-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Signed-off-by: Vaibhav Jain <vaibhav@linux.vnet.ibm.com>
Acked-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 13 insertions, 9 deletions

diff --git a/drivers/misc/cxl/file.c b/drivers/misc/cxl/file.c
index d0b421f49b39..77080cc5fa0a 100644
--- a/drivers/misc/cxl/file.c
+++ b/drivers/misc/cxl/file.c
@@ -194,6 +194,16 @@ static long afu_ioctl_start_work(struct cxl_context *ctx,
         ctx->mmio_err_ff = !!(work.flags & CXL_START_WORK_ERR_FF);
 
         /*
+         * Increment the mapped context count for adapter. This also checks
+         * if adapter_context_lock is taken.
+         */
+        rc = cxl_adapter_context_get(ctx->afu->adapter);
+        if (rc) {
+                afu_release_irqs(ctx, ctx);
+                goto out;
+        }
+
+        /*
          * We grab the PID here and not in the file open to allow for the case
          * where a process (master, some daemon, etc) has opened the chardev on
          * behalf of another process, so the AFU's mm gets bound to the process
@@ -205,15 +215,6 @@ static long afu_ioctl_start_work(struct cxl_context *ctx,
         ctx->pid = get_task_pid(current, PIDTYPE_PID);
         ctx->glpid = get_task_pid(current->group_leader, PIDTYPE_PID);
 
-        /*
-         * Increment the mapped context count for adapter. This also checks
-         * if adapter_context_lock is taken.
-         */
-        rc = cxl_adapter_context_get(ctx->afu->adapter);
-        if (rc) {
-                afu_release_irqs(ctx, ctx);
-                goto out;
-        }
 
         trace_cxl_attach(ctx, work.work_element_descriptor, work.num_interrupts, amr);
 
@@ -221,6 +222,9 @@ static long afu_ioctl_start_work(struct cxl_context *ctx,
                                                         amr))) {
                 afu_release_irqs(ctx, ctx);
                 cxl_adapter_context_put(ctx->afu->adapter);
+                put_pid(ctx->glpid);
+                put_pid(ctx->pid);
+                ctx->glpid = ctx->pid = NULL;
                 goto out;
         }