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kmsan: unpoison @tlb in arch_tlb_gather_mmu()

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This is an optimization to reduce stackdepot pressure.

struct mmu_gather contains 7 1-bit fields packed into a 32-bit unsigned
int value.  The remaining 25 bits remain uninitialized and are never used,
but KMSAN updates the origin for them in zap_pXX_range() in mm/memory.c,
thus creating very long origin chains.  This is technically correct, but
consumes too much memory.

Unpoisoning the whole structure will prevent creating such chains.

Link: https://lkml.kernel.org/r/20220905122452.2258262-20-glider@google.com
Signed-off-by: Alexander Potapenko <glider@google.com>
Acked-by: Marco Elver <elver@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 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: Liu Shixin <liushixin2@huawei.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: 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 2022-09-05 14:24:27 +02:00 committed by Andrew Morton
parent 4fa0e3ff21
commit ac801e7e25
1 changed files with 10 additions and 0 deletions
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10
mm/mmu_gather.c
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@ -1,6 +1,7 @@
#include <linux/gfp.h>
#include <linux/highmem.h>
#include <linux/kernel.h>
#include <linux/kmsan-checks.h>
#include <linux/mmdebug.h>
#include <linux/mm_types.h>
#include <linux/mm_inline.h>
@ -265,6 +266,15 @@ void tlb_flush_mmu(struct mmu_gather *tlb)
static void __tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm,
bool fullmm)
{
/*
* struct mmu_gather contains 7 1-bit fields packed into a 32-bit
* unsigned int value. The remaining 25 bits remain uninitialized
* and are never used, but KMSAN updates the origin for them in
* zap_pXX_range() in mm/memory.c, thus creating very long origin
* chains. This is technically correct, but consumes too much memory.
* Unpoisoning the whole structure will prevent creating such chains.
*/
kmsan_unpoison_memory(tlb, sizeof(*tlb));
tlb->mm = mm;
tlb->fullmm = fullmm;