linux-kernel - Re: [PATCH -next] selinux: Fix potential memory leak in selinux_add

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Message-ID: <CAHC9VhSwYdrHw8jNYxWApPYMjnmX-ZDN1=CzmRBeS1HoL-KOOA@mail.gmail.com>
Date:   Mon, 13 Jun 2022 16:22:46 -0400
From:   Paul Moore <paul@...l-moore.com>
To:     Xiu Jianfeng <xiujianfeng@...wei.com>
Cc:     stephen.smalley.work@...il.com, eparis@...isplace.org,
        omosnace@...hat.com, selinux@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next] selinux: Fix potential memory leak in selinux_add_opt

On Sat, Jun 11, 2022 at 5:07 AM Xiu Jianfeng <xiujianfeng@...wei.com> wrote:
>
> In the entry of selinux_add_opt, *mnt_opts may be assigned to new
> allocated memory, and also may be freed and reset at the end of the
> function. however, if security_context_str_to_sid failed, it returns
> directly and skips the procedure for free and reset, even if it may be
> handled at the caller of this function, It is better to handle it
> inside.
>
> Fixes: 70f4169ab421 ("selinux: parse contexts for mount options early")
> Signed-off-by: Xiu Jianfeng <xiujianfeng@...wei.com>
> ---
>  security/selinux/hooks.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)

Have you actually observed a memory leak from the selinux_mnt_opts
allocation in selinux_add_opt()?

The selinux_add_opt() function has two callers:
selinux_sb_eat_lsm_opts() and selinux_fs_context_parse_param().  The
former cleans up the selinux_mnt_opts allocation it its error handler
while the latter will end up calling
security_free_mnt_opts()/selinux_free_mnt_opts() to free the
fs_context:security when the fs_context is destroyed.

This patch shouldn't be necessary.

-- 
paul-moore.com