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Date: Fri, 26 Aug 2022 17:07:42 +0200 From: Alexander Potapenko <glider@...gle.com> To: glider@...gle.com Cc: Alexander Viro <viro@...iv.linux.org.uk>, Alexei Starovoitov <ast@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>, Andrey Konovalov <andreyknvl@...gle.com>, Andy Lutomirski <luto@...nel.org>, Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>, Christoph Hellwig <hch@....de>, Christoph Lameter <cl@...ux.com>, David Rientjes <rientjes@...gle.com>, Dmitry Vyukov <dvyukov@...gle.com>, Eric Dumazet <edumazet@...gle.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Herbert Xu <herbert@...dor.apana.org.au>, Ilya Leoshkevich <iii@...ux.ibm.com>, Ingo Molnar <mingo@...hat.com>, Jens Axboe <axboe@...nel.dk>, Joonsoo Kim <iamjoonsoo.kim@....com>, Kees Cook <keescook@...omium.org>, Marco Elver <elver@...gle.com>, Mark Rutland <mark.rutland@....com>, Matthew Wilcox <willy@...radead.org>, "Michael S. Tsirkin" <mst@...hat.com>, Pekka Enberg <penberg@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Petr Mladek <pmladek@...e.com>, Steven Rostedt <rostedt@...dmis.org>, Thomas Gleixner <tglx@...utronix.de>, Vasily Gorbik <gor@...ux.ibm.com>, Vegard Nossum <vegard.nossum@...cle.com>, Vlastimil Babka <vbabka@...e.cz>, kasan-dev@...glegroups.com, linux-mm@...ck.org, linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org Subject: [PATCH v5 19/44] kmsan: unpoison @tlb in arch_tlb_gather_mmu() 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. Signed-off-by: Alexander Potapenko <glider@...gle.com> Acked-by: Marco Elver <elver@...gle.com> --- v5: -- updated description as suggested by Marco Elver Link: https://linux-review.googlesource.com/id/I76abee411b8323acfdbc29bc3a60dca8cff2de77 --- mm/mmu_gather.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/mm/mmu_gather.c b/mm/mmu_gather.c index a71924bd38c0d..add4244e5790d 100644 --- a/mm/mmu_gather.c +++ b/mm/mmu_gather.c @@ -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; -- 2.37.2.672.g94769d06f0-goog
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