From 305e519ce48e935702c32241f07d393c3c8fed3e Mon Sep 17 00:00:00 2001
From: Alexander Potapenko <glider@google.com>
Date: Thu, 20 Feb 2020 20:04:30 -0800
Subject: [PATCH] lib/stackdepot.c: fix global out-of-bounds in stack_slabs
Git-commit: 305e519ce48e935702c32241f07d393c3c8fed3e
Patch-mainline: v5.6-rc3
References: git fixes (block drivers)
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.
(Coly Li: rebased for fixes/linux-4.12 code base)
Link: http://lkml.kernel.org/r/20200218102950.260263-1-glider@google.com
Fixes: cd11016e5f521 ("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: Coly Li <colyli@suse.de>
---
lib/stackdepot.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
--- a/lib/stackdepot.c
+++ b/lib/stackdepot.c
@@ -92,15 +92,19 @@ static bool init_stack_slab(void **preal
return true;
if (stack_slabs[depot_index] == NULL) {
stack_slabs[depot_index] = *prealloc;
+ *prealloc = NULL;
} else {
- stack_slabs[depot_index + 1] = *prealloc;
+ /* If this is the last depot slab, do not touch the next one. */
+ if (depot_index + 1 < STACK_ALLOC_MAX_SLABS) {
+ stack_slabs[depot_index + 1] = *prealloc;
+ *prealloc = NULL;
+ }
/*
* This smp_store_release pairs with smp_load_acquire() from
* |next_slab_inited| above and in depot_save_stack().
*/
smp_store_release(&next_slab_inited, 1);
}
- *prealloc = NULL;
return true;
}