2023-06-15 03:35:07

by Jiasheng Jiang

Subject: [PATCH v2] pstore/platform: Add check for kstrdup

Add check for the return value of kstrdup() and return the error
if it fails in order to avoid NULL pointer dereference.

Fixes: 563ca40ddf40 ("pstore/platform: Switch pstore_info::name to const")
Signed-off-by: Jiasheng Jiang <[email protected]>
---
Changelog:

v1 -> v2:

1. Allocate a copy earlier.
---
fs/pstore/platform.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index cbc0b468c1ab..727f8ce71062 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -573,6 +573,8 @@ static int pstore_write_user_compat(struct pstore_record *record,
*/
int pstore_register(struct pstore_info *psi)
{
+ char *new_backend;
+
if (backend && strcmp(backend, psi->name)) {
pr_warn("backend '%s' already in use: ignoring '%s'\n",
backend, psi->name);
@@ -593,6 +595,10 @@ int pstore_register(struct pstore_info *psi)
return -EINVAL;
}

+ new_backend = kstrdup(psi->name, GFP_KERNEL);
+ if (!new_backend)
+ return -ENOMEM;
+
mutex_lock(&psinfo_lock);
if (psinfo) {
pr_warn("backend '%s' already loaded: ignoring '%s'\n",
@@ -630,7 +636,7 @@ int pstore_register(struct pstore_info *psi)
* Update the module parameter backend, so it is visible
* through /sys/module/pstore/parameters/backend
*/
- backend = kstrdup(psi->name, GFP_KERNEL);
+ backend = new_backend;

pr_info("Registered %s as persistent store backend\n", psi->name);

--
2.25.1

2023-06-22 16:32:58

by Kees Cook

Subject: Re: [PATCH v2] pstore/platform: Add check for kstrdup

On Thu, Jun 15, 2023 at 10:53:12AM +0800, Jiasheng Jiang wrote:
> Add check for the return value of kstrdup() and return the error
> if it fails in order to avoid NULL pointer dereference.
>
> Fixes: 563ca40ddf40 ("pstore/platform: Switch pstore_info::name to const")
> Signed-off-by: Jiasheng Jiang <[email protected]>

Thanks, this is looking better!

> ---
> Changelog:
>
> v1 -> v2:
>
> 1. Allocate a copy earlier.
> ---
> fs/pstore/platform.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
> index cbc0b468c1ab..727f8ce71062 100644
> --- a/fs/pstore/platform.c
> +++ b/fs/pstore/platform.c
> @@ -573,6 +573,8 @@ static int pstore_write_user_compat(struct pstore_record *record,
> */
> int pstore_register(struct pstore_info *psi)
> {
> + char *new_backend;
> +
> if (backend && strcmp(backend, psi->name)) {
> pr_warn("backend '%s' already in use: ignoring '%s'\n",
> backend, psi->name);
> @@ -593,6 +595,10 @@ int pstore_register(struct pstore_info *psi)
> return -EINVAL;
> }
>
> + new_backend = kstrdup(psi->name, GFP_KERNEL);
> + if (!new_backend)
> + return -ENOMEM;
> +
> mutex_lock(&psinfo_lock);
> if (psinfo) {
> pr_warn("backend '%s' already loaded: ignoring '%s'\n",

In my suggestion I had included a kfree() for new_backend in this above
error path, which is missing here. Can you respin it with that added?

> @@ -630,7 +636,7 @@ int pstore_register(struct pstore_info *psi)
> * Update the module parameter backend, so it is visible
> * through /sys/module/pstore/parameters/backend
> */
> - backend = kstrdup(psi->name, GFP_KERNEL);
> + backend = new_backend;
>
> pr_info("Registered %s as persistent store backend\n", psi->name);
>
> --
> 2.25.1
>

But otherwise, yeah, looks good. Thanks!

--
Kees Cook