From: Kees Cook keescook@chromium.org
[ 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
Cc: Juergen Gross jgross@suse.com Cc: Boris Ostrovsky boris.ostrovsky@oracle.com Cc: Thomas Gleixner tglx@linutronix.de Cc: Ingo Molnar mingo@redhat.com Cc: Borislav Petkov bp@alien8.de Cc: Dave Hansen dave.hansen@linux.intel.com Cc: x86@kernel.org Cc: "H. Peter Anvin" hpa@zytor.com Cc: xen-devel@lists.xenproject.org Reviewed-by: Boris Ostrovsky boris.ostrovsky@oracle.com Link: https://lore.kernel.org/lkml/41527d69-e8ab-3f86-ff37-6b298c01d5bc@oracle.com Signed-off-by: Kees Cook keescook@chromium.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/xen/enlighten_pv.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c index 804c65d2b95f..815030b7f6fa 100644 --- a/arch/x86/xen/enlighten_pv.c +++ b/arch/x86/xen/enlighten_pv.c @@ -768,6 +768,7 @@ 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); @@ -777,7 +778,7 @@ 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))