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SubjectRe: [PATCH] security/selinux: fix potential memleak
On Wed, Dec 1, 2021 at 10:35 PM Bernard Zhao <bernard@vivo.com> wrote:
>
> This patch try to fix potential memleak in function
> selinux_fs_context_dup`s error branch.
>
> Signed-off-by: Bernard Zhao <bernard@vivo.com>
> ---
> security/selinux/hooks.c | 22 ++++++++++++++++++----
> 1 file changed, 18 insertions(+), 4 deletions(-)
>
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 62d30c0a30c2..36d7fc373839 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -2856,24 +2856,38 @@ static int selinux_fs_context_dup(struct fs_context *fc,
> if (src->fscontext) {
> opts->fscontext = kstrdup(src->fscontext, GFP_KERNEL);
> if (!opts->fscontext)
> - return -ENOMEM;
> + goto err_fscontext;
> }
> if (src->context) {
> opts->context = kstrdup(src->context, GFP_KERNEL);
> if (!opts->context)
> - return -ENOMEM;
> + goto err_context;
> }
> if (src->rootcontext) {
> opts->rootcontext = kstrdup(src->rootcontext, GFP_KERNEL);
> if (!opts->rootcontext)
> - return -ENOMEM;
> + goto err_rootcontext;
> }
> if (src->defcontext) {
> opts->defcontext = kstrdup(src->defcontext, GFP_KERNEL);
> if (!opts->defcontext)
> - return -ENOMEM;
> + goto err_defcontext;
> }
> return 0;
> +
> +err_defcontext:
> + if (src->rootcontext)
> + kfree(opts->rootcontext);
> +err_rootcontext:
> + if (src->context)
> + kfree(opts->context);
> +err_context:
> + if (src->fscontext)
> + kfree(opts->fscontext);
> +err_fscontext:
> + kfree(fc->security);
> +
> + return -ENOMEM;
> }

Thanks for catching this a providing a patch, however I think the
memory cleanup can be made simpler, see the pseudo code below:

static int selinux_fs_context_dup(...)
{

fc->security = kzalloc(...);
if (!fc->security)
return -ENOMEM;

opts = fc->security;

if (src->fscontext) {
opts->fscontext = kstrdup(...);
if (!opts->fscontext)
goto err;
}

/* ... */

return 0;

err:
kfree(opts->fscontext);
kfree(opts->context);
kfree(opts->rootcontext);
kfree(opts->defcontext);
kfree(opts);
fc->security = NULL;
return -ENOMEM;
}

--
paul moore
www.paul-moore.com

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