2024-01-12 05:49:47

by Kunwu Chan

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

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 <[email protected]>
Cc: Kunwu Chan <[email protected]>
Suggested-by: Frederic Barrat <[email protected]>
---
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

2024-01-15 05:03:48

by Andrew Donnellan

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

On Fri, 2024-01-12 at 13:49 +0800, Kunwu Chan wrote:

> +err:
> + if (rc < 0)
> + return ERR_PTR(rc);
>   return NULL;

I don't think there's a way for this NULL to ever get returned?

Apart from that it looks good:

Reviewed-by: Andrew Donnellan <[email protected]>

--
Andrew Donnellan OzLabs, ADL Canberra
[email protected] IBM Australia Limited

2024-01-15 11:06:03

by Frederic Barrat

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

On 12/01/2024 06:49, Kunwu Chan wrote:
> 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 <[email protected]>
> Cc: Kunwu Chan <[email protected]>
> Suggested-by: Frederic Barrat <[email protected]>
> ---

Thanks!
Acked-by: Frederic Barrat <[email protected]>

Fred


> 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);