Re: [PATCH] audit: fix undefined behavior in bit shift for AUDIT_BIT
On 2022-10-31 07:34, Paul Moore wrote:
On Sun, Oct 30, 2022 at 10:10 PM Gaosheng Cui
<cuigaosheng1(a)huawei.com> wrote:
>
> Shifting signed 32-bit value by 31 bits is undefined, so changing
> significant bit to unsigned. The UBSAN warning calltrace like below:
>
> UBSAN: shift-out-of-bounds in kernel/auditfilter.c:179:23
> left shift of 1 by 31 places cannot be represented in type 'int'
> Call Trace:
> <TASK>
> dump_stack_lvl+0x7d/0xa5
> dump_stack+0x15/0x1b
> ubsan_epilogue+0xe/0x4e
> __ubsan_handle_shift_out_of_bounds+0x1e7/0x20c
> audit_register_class+0x9d/0x137
> audit_classes_init+0x4d/0xb8
> do_one_initcall+0x76/0x430
> kernel_init_freeable+0x3b3/0x422
> kernel_init+0x24/0x1e0
> ret_from_fork+0x1f/0x30
> </TASK>
>
> Fixes: 607ca46e97a1 ("UAPI: (Scripted) Disintegrate include/linux")
Thanks, this patch looks good, although the 'Fixes:' line above isn't
correct. The commit you reference may be the commit which created
AUDIT_BIT in include/uapi/linux/audit.h, but before that it was
defined in include/linux/audit.h with the original implementation
shipping in v2.6.6-rc1. As the original AUDIT_BIT implementation
predates git itself, I would suggest removing the 'Fixes' line
entirely and I'll simply add the usual stable marking when I merge it
into audit/stable-6.1. If that is okay with you I'll go ahead and
merge this patch which that tweak - is that okay?
In fact, it is the original kernel audit subsystem commit if you join
the 3 trees that went in to Linux 2.6.6-rc1:
commit b7b0074ca3c9fe22d07b97e42a99c8b27be6307f
Author: Andrew Morton <akpm(a)osdl.org>
AuthorDate: 2004-04-11 23:29:12 -0700
Commit: Linus Torvalds <torvalds(a)ppc970.osdl.org>
CommitDate: 2004-04-11 23:29:12 -0700
[PATCH] Light-weight Auditing Framework
From: Rik Faith <faith(a)redhat.com>
> Signed-off-by: Gaosheng Cui <cuigaosheng1(a)huawei.com>
> ---
> include/uapi/linux/audit.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
> index 7c1dc818b1d5..d676ed2b246e 100644
> --- a/include/uapi/linux/audit.h
> +++ b/include/uapi/linux/audit.h
> @@ -187,7 +187,7 @@
> #define AUDIT_MAX_KEY_LEN 256
> #define AUDIT_BITMASK_SIZE 64
> #define AUDIT_WORD(nr) ((__u32)((nr)/32))
> -#define AUDIT_BIT(nr) (1 << ((nr) - AUDIT_WORD(nr)*32))
> +#define AUDIT_BIT(nr) (1U << ((nr) - AUDIT_WORD(nr)*32))
>
> #define AUDIT_SYSCALL_CLASSES 16
> #define AUDIT_CLASS_DIR_WRITE 0
> --
> 2.25.1
--
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