linux-kernel - Re: [PATCH 7/9] Simplify bound checks in capabilities for copy_from

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <21d7e9970909282255y6718b11cvadafae0e1648817c@mail.gmail.com>
Date:	Tue, 29 Sep 2009 15:55:49 +1000
From:	Dave Airlie <airlied@...il.com>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	mingo@...e.hu, jmorris@...i.org
Subject: Re: [PATCH 7/9] Simplify bound checks in capabilities for 
	copy_from_user

On Sun, Sep 27, 2009 at 4:53 AM, Arjan van de Ven <arjan@...radead.org> wrote:
> From: Arjan van de Ven <arjan@...ux.intel.com>
> Subject: [PATCH 7/9] Simplify bound checks in capabilities for copy_from_user
> CC: James Morris <jmorris@...ei.org>
>
> The capabilities syscall has a copy_from_user() call where gcc currently
> cannot prove to itself that the copy is always within bounds.
>
> This patch adds a very explicity bound check to prove to gcc that
> this copy_from_user cannot overflow its destination buffer.
>
> Signed-off-by: Arjan van de Ven <arjan@...ux.intel.com>
>
> diff --git a/kernel/capability.c b/kernel/capability.c
> index 4e17041..204f11f 100644
> --- a/kernel/capability.c
> +++ b/kernel/capability.c
> @@ -238,7 +241,7 @@ SYSCALL_DEFINE2(capget, cap_user_header_t, header, cap_user_data_t, dataptr)
>  SYSCALL_DEFINE2(capset, cap_user_header_t, header, const cap_user_data_t, data)
>  {
>        struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
> -       unsigned i, tocopy;
> +       unsigned i, tocopy, copybytes;
>        kernel_cap_t inheritable, permitted, effective;
>        struct cred *new;
>        int ret;
> @@ -255,8 +258,11 @@ SYSCALL_DEFINE2(capset, cap_user_header_t, header, const cap_user_data_t, data)
>        if (pid != 0 && pid != task_pid_vnr(current))
>                return -EPERM;
>
> -       if (copy_from_user(&kdata, data,
> -                          tocopy * sizeof(struct __user_cap_data_struct)))
> +       copybytes = tocopy * sizeof(struct __user_cap_data_struct);
> +       if (copybytes > _KERNEL_CAPABILITY_U32S)
> +               return -EFAULT;

This is broken, it breaks dbus at least for me. you compare bytes
to u32s wrongly.

Dave.

> +
> +       if (copy_from_user(&kdata, data, copybytes))
>                return -EFAULT;
>
>        for (i = 0; i < tocopy; i++) {
>
>
>
> --
> Arjan van de Ven        Intel Open Source Technology Centre
> For development, discussion and tips for power savings,
> visit http://www.lesswatts.org
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@...r.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/