[PATCH] audit: fix undefined behavior in bit shift for AUDIT_BIT

[Richard Guy Briggs]

On 2022-10-31 07:34, Paul Moore wrote:
> On Sun, Oct 30, 2022 at 10:10 PM Gaosheng Cui <cuigaosheng1 at 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 at osdl.org>
AuthorDate: 2004-04-11 23:29:12 -0700
Commit:     Linus Torvalds <torvalds at ppc970.osdl.org>
CommitDate: 2004-04-11 23:29:12 -0700

    [PATCH] Light-weight Auditing Framework
    
    From: Rik Faith <faith at redhat.com>

> > Signed-off-by: Gaosheng Cui <cuigaosheng1 at 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
> 
> --
> paul-moore.com
> 
> --
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> 

- RGB

--
Richard Guy Briggs <rgb at redhat.com>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
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