[RESEND PATCH] cxl: Fix leaking pid refs in some error paths

* [RESEND PATCH] cxl: Fix leaking pid refs in some error paths
@ 2016-10-21  9:23 Vaibhav Jain
  2016-10-21 17:34   ` Frederic Barrat
  2016-10-26 10:21 ` [RESEND] " Michael Ellerman
  0 siblings, 2 replies; 4+ messages in thread
From: Vaibhav Jain @ 2016-10-21  9:23 UTC (permalink / raw)
  To: Frederic Barrat, linuxppc-dev
  Cc: Vaibhav Jain, Ian Munsie, Andrew Donnellan, Christophe Lombard,
	Philippe Bergheaud, gkurz, stable

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: 7b8ad495("cxl: Fix DSI misses when the context owning task exits")
Cc: stable@vger.kernel.org
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>
---
This patch is based on earlier patch "cxl: Prevent adapter reset
if an active context exists" at
https://patchwork.ozlabs.org/patch/682187/

Changelog:
RESEND ->	* Marked the patch for stable tree.
       		* Moved the patch dependency text under '---' area
		* Added Andrew Donnellan's review sign-off
---
 drivers/misc/cxl/api.c  |  2 ++
 drivers/misc/cxl/file.c | 22 +++++++++++++---------
 2 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/drivers/misc/cxl/api.c b/drivers/misc/cxl/api.c
index af23d7d..2e5233b 100644
--- a/drivers/misc/cxl/api.c
+++ b/drivers/misc/cxl/api.c
@@ -247,7 +247,9 @@ int cxl_start_context(struct cxl_context *ctx, u64 wed,
 	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;
diff --git a/drivers/misc/cxl/file.c b/drivers/misc/cxl/file.c
index d0b421f..77080cc 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;
 	}
 
-- 
2.7.4


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