Messages in this thread | | | Date | Wed, 10 Dec 2008 21:41:42 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH] fix calls to request_module() |
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On Wed, 10 Dec 2008 21:03:37 -0800 Roland Dreier <rdreier@cisco.com> wrote:
> The kernel has such code eg in init/main.c, which does > > printk(linux_banner); > > when linux_banner is only visible to the compiler as > > extern const char linux_banner[]; > > however the trivial fix > > diff --git a/init/main.c b/init/main.c > index 7e117a2..e471598 100644 > --- a/init/main.c > +++ b/init/main.c > @@ -568,7 +568,7 @@ asmlinkage void __init start_kernel(void) > boot_cpu_init(); > page_address_init(); > printk(KERN_NOTICE); > - printk(linux_banner); > + printk("%s", linux_banner); > setup_arch(&command_line); > mm_init_owner(&init_mm, &init_task); > setup_command_line(command_line); > > doesn't seem that appealing, since it bloats the object code for a > non-bug -- 7 bytes for me on x86_64: > > add/remove: 0/0 grow/shrink: 1/0 up/down: 7/0 (7) > function old new delta > start_kernel 680 687 +7 > > given the number of such warnings I see in a typical compile, this would > be a fairly hefty amount of bloat just to shut up gcc.
yes, that would suck. otoh, our current warning spew actually causes bugs.
I wonder if we could add a printk_stfu() which isn't declared attribute(printf) and which simply calls printk. We might still get a single warning at the interface point.
> On the other hand, gcc warning on such code (untrusted format string > passed into a printf-like function) seems quite legitimate as well.
Yes, we've had actual bugs in the kernel from this, where the control string was user-provided. root-only user, fortunately.
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