[PATCH] cxl: Fix struct pid leak when attaching a process through kernel API

[PATCH] cxl: Fix struct pid leak when attaching a process through kernel API

[Frederic Barrat]

When the cxl driver creates a context, it stores the pid of the
calling task, and mistakenly increments the reference count of the
struct pid twice, once through get_task_pid(), once through
get_pid(). The reference count is only decremented once on detach. As
a result, a struct pid is leaked and it reduces the number of
processes that can run simultaneously by one.
The fix is to simply remove the call to get_pid().

There is a separate patch for the user API, since it goes to
different kernel versions.

Signed-off-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Cc: <stable@vger.kernel.org> # 4.3+
---
 drivers/misc/cxl/api.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/misc/cxl/api.c b/drivers/misc/cxl/api.c
index 103baf0..94b6627 100644
--- a/drivers/misc/cxl/api.c
+++ b/drivers/misc/cxl/api.c
@@ -176,7 +176,6 @@ int cxl_start_context(struct cxl_context *ctx, u64 wed,
 
 	if (task) {
 		ctx->pid = get_task_pid(task, PIDTYPE_PID);
-		get_pid(ctx->pid);
 		kernel = false;
 	}
 
-- 
1.9.1

Re: [PATCH] cxl: Fix struct pid leak when attaching a process through kernel API

[Ian Munsie]

Acked-by: Ian Munsie <imunsie@au1.ibm.com>

Re: [PATCH] cxl: Fix struct pid leak when attaching a process through kernel API

[Andrew Donnellan]

On 03/11/15 23:20, Frederic Barrat wrote:
> When the cxl driver creates a context, it stores the pid of the
> calling task, and mistakenly increments the reference count of the
> struct pid twice, once through get_task_pid(), once through
> get_pid(). The reference count is only decremented once on detach. As
> a result, a struct pid is leaked and it reduces the number of
> processes that can run simultaneously by one.
> The fix is to simply remove the call to get_pid().
>
> There is a separate patch for the user API, since it goes to
> different kernel versions.
>
> Signed-off-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
> Cc: <stable@vger.kernel.org> # 4.3+

Reviewed-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>

-- 
Andrew Donnellan              Software Engineer, OzLabs
andrew.donnellan@au1.ibm.com  Australia Development Lab, Canberra
+61 2 6201 8874 (work)        IBM Australia Limited