lib/stackdepot.c: fix global out-of-bounds in stack_slabs

stable inclusion
from stable-v4.19.107
commit da3418ad747fa035a1a88c6883dd2c7d7142ffc4
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I787JE
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=305e519ce48e935702c32241f07d393c3c8fed3e

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

[ Upstream commit 305e519c ]

Walter Wu has reported a potential case in which init_stack_slab() is
called after stack_slabs[STACK_ALLOC_MAX_SLABS - 1] has already been
initialized.  In that case init_stack_slab() will overwrite
stack_slabs[STACK_ALLOC_MAX_SLABS], which may result in a memory
corruption.

Link: http://lkml.kernel.org/r/20200218102950.260263-1-glider@google.com


Fixes: cd11016e ("mm, kasan: stackdepot implementation. Enable stackdepot for SLAB")
Signed-off-by: Alexander Potapenko <glider@google.com>
Reported-by: Walter Wu <walter-zh.wu@mediatek.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Ye Weihua <yeweihua4@huawei.com>
Reviewed-by: Nanyong Sun <sunnanyong@huawei.com>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>