[PATCH 4.8 035/138] cxl: Fix leaking pid refs in some error paths

[Greg Kroah-Hartman]

4.8-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Vaibhav Jain <vaib...@linux.vnet.ibm.com>

commit a05b82d5149dfeef05254a11c3636a89a854520a upstream.

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")
Reviewed-by: Andrew Donnellan <andrew.donnel...@au1.ibm.com>
Reported-by: Frederic Barrat <fbar...@linux.vnet.ibm.com>
Signed-off-by: Vaibhav Jain <vaib...@linux.vnet.ibm.com>
Acked-by: Frederic Barrat <fbar...@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <m...@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 drivers/misc/cxl/api.c  |    2 ++
 drivers/misc/cxl/file.c |   22 +++++++++++++---------
 2 files changed, 15 insertions(+), 9 deletions(-)

--- a/drivers/misc/cxl/api.c
+++ b/drivers/misc/cxl/api.c
@@ -247,7 +247,9 @@ int cxl_start_context(struct cxl_context
        cxl_ctx_get();
 
        if ((rc = cxl_ops->attach_process(ctx, kernel, wed, 0))) {
+               put_pid(ctx->glpid);
                put_pid(ctx->pid);
+               ctx->glpid = ctx->pid = NULL;
                cxl_adapter_context_put(ctx->afu->adapter);
                cxl_ctx_put();
                goto out;
--- a/drivers/misc/cxl/file.c
+++ b/drivers/misc/cxl/file.c
@@ -194,6 +194,16 @@ static long afu_ioctl_start_work(struct
        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
        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
                                                        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;
        }