[PATCH 3/3] cxl: fix leak of ctx->mapping when releasing kernel API contexts

Andrew Donnellan andrew.donnellan at au1.ibm.com
Wed Sep 30 11:58:07 AEST 2015

When a context is created via the kernel API, ctx->mapping is allocated
within the kernel and thus needs to be freed when the context is freed.
reclaim_ctx() attempts to do this for contexts with the ctx->kernelapi flag
set, but afu_release() (which can be called from the kernel API through
cxl_fd_release()) sets ctx->mapping to NULL before calling
cxl_context_free() to free the context.

Add a check to afu_release() so that the mappings in contexts created via
the kernel API are left alone so reclaim_ctx() can free them.

Reported-by: Matthew R. Ochs <mrochs at linux.vnet.ibm.com>
Fixes: 6f7f0b3df6d4 ("cxl: Add AFU virtual PHB and kernel API")
Signed-off-by: Andrew Donnellan <andrew.donnellan at au1.ibm.com>
 drivers/misc/cxl/file.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/misc/cxl/file.c b/drivers/misc/cxl/file.c
index a30bf28..fcda6b0 100644
--- a/drivers/misc/cxl/file.c
+++ b/drivers/misc/cxl/file.c
@@ -120,9 +120,16 @@ int afu_release(struct inode *inode, struct file *file)
 		 __func__, ctx->pe);
-	mutex_lock(&ctx->mapping_lock);
-	ctx->mapping = NULL;
-	mutex_unlock(&ctx->mapping_lock);
+	/* 
+	 * Delete the context's mapping pointer, unless it's created by the
+	 * kernel API, in which case leave it so it can be freed by reclaim_ctx()
+	 */
+	if (!ctx->kernelapi) {
+		mutex_lock(&ctx->mapping_lock);
+		ctx->mapping = NULL;
+		mutex_unlock(&ctx->mapping_lock);
+	}
Andrew Donnellan              Software Engineer, OzLabs
andrew.donnellan at au1.ibm.com  Australia Development Lab, Canberra
+61 2 6201 8874 (work)        IBM Australia Limited

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