This is a note to let you know that I've just added the patch titled
x86/entry: Work around Clang __bdos() bug
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-entry-work-around-clang-__bdos-bug.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 700fcd28dfafb4eb61b209126a99d607b6e7da7c
Author: Kees Cook <keescook@xxxxxxxxxxxx>
Date: Mon Sep 19 19:45:14 2022 -0700
x86/entry: Work around Clang __bdos() bug
[ 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@xxxxxxxx>
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: x86@xxxxxxxxxx
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Link: https://lore.kernel.org/lkml/41527d69-e8ab-3f86-ff37-6b298c01d5bc@xxxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
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))
