Hi! > From: Kees Cook <[email protected]> > > [ Upstream commit 3e1730842f142add55dc658929221521a9ea62b6 ] > > Clang produces a false positive when building with CONFIG_FORTIFY_SOURCE=y > and CONFIG_UBSAN_BOUNDS=y when operating on an array with a dynamic > offset. Work around this by using a direct assignment of an empty > instance. Avoids this warning: > > ../include/linux/fortify-string.h:309:4: warning: call to > __write_overflow_field declared with 'warn > ing' attribute: detected write beyond size of field (1st parameter); maybe > use struct_group()? [-Wat > tribute-warning] > __write_overflow_field(p_size_field, size); > ^ > > which was isolated to the memset() call in xen_load_idt(). > > Note that this looks very much like another bug that was worked around: > https://github.com/ClangBuiltLinux/linux/issues/1592
At least in 4.19, there's no UBSAN_BOUNDS. Sounds like we don't need
it in old kernels?
Best regards,
Pavel
> +++ b/arch/x86/xen/enlighten_pv.c
> @@ -752,6 +752,7 @@ static void xen_load_idt(const struct desc_ptr *desc)
> {
> static DEFINE_SPINLOCK(lock);
> static struct trap_info traps[257];
> + static const struct trap_info zero = { };
> unsigned out;
>
> trace_xen_cpu_load_idt(desc);
> @@ -761,7 +762,7 @@ static void xen_load_idt(const struct desc_ptr *desc)
> memcpy(this_cpu_ptr(&idt_desc), desc, sizeof(idt_desc));
>
> out = xen_convert_trap_info(desc, traps, false);
> - memset(&traps[out], 0, sizeof(traps[0]));
> + traps[out] = zero;
>
> xen_mc_flush();
> if (HYPERVISOR_set_trap_table(traps))
> --
> 2.35.1
--
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