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kcov: kmsan: unpoison area->list in kcov_remote_area_put()

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KMSAN does not instrument kernel/kcov.c for performance reasons (with
CONFIG_KCOV=y virtually every place in the kernel invokes kcov
instrumentation).  Therefore the tool may miss writes from kcov.c that
initialize memory.

When CONFIG_DEBUG_LIST is enabled, list pointers from kernel/kcov.c are
passed to instrumented helpers in lib/list_debug.c, resulting in false
positives.

To work around these reports, we unpoison the contents of area->list after
initializing it.

Link: https://lkml.kernel.org/r/20220915150417.722975-30-glider@google.com
Signed-off-by: Alexander Potapenko <glider@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Ilya Leoshkevich <iii@linux.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Marco Elver <elver@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Alexander Potapenko 2022-09-15 17:04:03 +02:00 committed by Andrew Morton
parent 11b331f857
commit 74d8990988
1 changed files with 7 additions and 0 deletions
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7
kernel/kcov.c
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@ -11,6 +11,7 @@
#include <linux/fs.h>
#include <linux/hashtable.h>
#include <linux/init.h>
#include <linux/kmsan-checks.h>
#include <linux/mm.h>
#include <linux/preempt.h>
#include <linux/printk.h>
@ -152,6 +153,12 @@ static void kcov_remote_area_put(struct kcov_remote_area *area,
INIT_LIST_HEAD(&area->list);
area->size = size;
list_add(&area->list, &kcov_remote_areas);
/*
* KMSAN doesn't instrument this file, so it may not know area->list
* is initialized. Unpoison it explicitly to avoid reports in
* kcov_remote_area_get().
*/
kmsan_unpoison_memory(&area->list, sizeof(area->list));
}
static notrace bool check_kcov_mode(enum kcov_mode needed_mode, struct task_struct *t)