[PATCH v2] cxl: Fix null pointer dereference in cxl_get_fd

[Kunwu Chan]

kasprintf() returns a pointer to dynamically allocated memory
which can be NULL upon failure.

Uniformly handle resource release in error paths. And when an
error occurs, an error pointer should be returned.

Fixes: bdecf76e319a ("cxl: Fix coredump generation when cxl_get_fd() is used")
Signed-off-by: Kunwu Chan <chen...@kylinos.cn>
Cc: Kunwu Chan <kunwu.c...@hotmail.com>
Suggested-by: Frederic Barrat <fbar...@linux.ibm.com>
---
v2: Deal with error path
---
 drivers/misc/cxl/api.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/drivers/misc/cxl/api.c b/drivers/misc/cxl/api.c
index d85c56530863..b49bc3d29fc0 100644
--- a/drivers/misc/cxl/api.c
+++ b/drivers/misc/cxl/api.c
@@ -389,19 +389,22 @@ struct file *cxl_get_fd(struct cxl_context *ctx, struct 
file_operations *fops,
                        int *fd)
 {
        struct file *file;
-       int rc, flags, fdtmp;
+       int rc = 0, flags, fdtmp;
        char *name = NULL;
 
        /* only allow one per context */
-       if (ctx->mapping)
-               return ERR_PTR(-EEXIST);
+       if (ctx->mapping) {
+               rc = -EEXIST;
+               goto err;
+       }
 
        flags = O_RDWR | O_CLOEXEC;
 
        /* This code is similar to anon_inode_getfd() */
        rc = get_unused_fd_flags(flags);
        if (rc < 0)
-               return ERR_PTR(rc);
+               goto err;
+
        fdtmp = rc;
 
        /*
@@ -419,6 +422,10 @@ struct file *cxl_get_fd(struct cxl_context *ctx, struct 
file_operations *fops,
                fops = (struct file_operations *)&afu_fops;
 
        name = kasprintf(GFP_KERNEL, "cxl:%d", ctx->pe);
+       if (!name) {
+               rc = -ENOMEM;
+               goto err_fd;
+       }
        file = cxl_getfile(name, fops, ctx, flags);
        kfree(name);
        if (IS_ERR(file))
@@ -430,6 +437,9 @@ struct file *cxl_get_fd(struct cxl_context *ctx, struct 
file_operations *fops,
 
 err_fd:
        put_unused_fd(fdtmp);
+err:
+       if (rc < 0)
+               return ERR_PTR(rc);
        return NULL;
 }
 EXPORT_SYMBOL_GPL(cxl_get_fd);
-- 
2.39.2