stable inclusion
from linux-4.19.164
commit b207caff4176e3a6ba273243da2db2e595e4aad2
CVE: CVE-2021-0938

--------------------------------

commit 3347acc6 upstream.

Commit 815f0ddb ("include/linux/compiler*.h: make compiler-*.h
mutually exclusive") neglected to copy barrier_data() from
compiler-gcc.h into compiler-clang.h.

The definition in compiler-gcc.h was really to work around clang's more
aggressive optimization, so this broke barrier_data() on clang, and
consequently memzero_explicit() as well.

For example, this results in at least the memzero_explicit() call in
lib/crypto/sha256.c:sha256_transform() being optimized away by clang.

Fix this by moving the definition of barrier_data() into compiler.h.

Also move the gcc/clang definition of barrier() into compiler.h,
__memory_barrier() is icc-specific (and barrier() is already defined
using it in compiler-intel.h) and doesn't belong in compiler.h.

[rdunlap@infradead.org: fix ALPHA builds when SMP is not enabled]

Link: https://lkml.kernel.org/r/20201101231835.4589-1-rdunlap@infradead.org
Fixes: 815f0ddb ("include/linux/compiler*.h: make compiler-*.h mutually exclusive")
Signed-off-by: NArvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: NRandy Dunlap <rdunlap@infradead.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Tested-by: NNick Desaulniers <ndesaulniers@google.com>
Reviewed-by: NNick Desaulniers <ndesaulniers@google.com>
Reviewed-by: NKees Cook <keescook@chromium.org>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20201014212631.207844-1-nivedita@alum.mit.eduSigned-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
[nd: backport to account for missing
  commit e506ea45 ("compiler.h: Split {READ,WRITE}_ONCE definitions out into rwonce.h")
  commit d08b9f0c ("scs: Add support for Clang's Shadow Call Stack (SCS)")
  commit a3f8a30f ("Compiler Attributes: use feature checks instead of version checks")]
Signed-off-by: NNick Desaulniers <ndesaulniers@google.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Reviewed-by: NCheng Jian <cj.chengjian@huawei.com>
Reviewed-by: NXiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>