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b=IanaUHsbwsrPyXz0XY9VEXXk/gyZBy4mrUr33oo2NC24Ta1Q3FzFfradVZuC9IRKZ knaIeGfU+HOmh2HFBoWNHLsUxN2b6q33uRtLmh74swNkkK5ys4VU8Xtsk3e2esq4gz UeDCfGv8BTlY7sD2R/k5eipIs/M0lXV7Bf0LGB4E= Date: Thu, 25 Jan 2024 17:34:48 -0800 From: Andrew Morton To: Alexander Potapenko Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, kasan-dev@googlegroups.com, Marco Elver , Dmitry Vyukov , Ilya Leoshkevich , Nicholas Miehlbradt Subject: Re: [PATCH v2] mm: kmsan: remove runtime checks from kmsan_unpoison_memory() Message-Id: <20240125173448.e866d84cda146145cbc67c93@linux-foundation.org> In-Reply-To: <20240124173134.1165747-1-glider@google.com> References: <20240124173134.1165747-1-glider@google.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 5A702180009 X-Stat-Signature: p1j74iww56r9i7i53bmogcnwc5ftk87w X-Rspam-User: X-HE-Tag: 1706232897-769930 X-HE-Meta: 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 mXyNFEz0 eSPw/Zp80raKbnDhWzVfNYcNyGwyBwBGpVJ6Wq7GUQqdNDrDKi6e1/Tx3QRu5x6YYxhwEkCFf8vGoJ3GZuruJzvSEbbt9Eong2ROSYlB0IgTrNAbyAiJFOtH9tO/DjPbxQ0tk9wJ9VfuBFt3XZo9or0q8abYfpd4HEiIVXCD71v45stLRyQ70fVokGVzzTfaFmufgXQcVqWXhWjYuHf1xRFQDBi+v1zo1qsxwi635pltWvmircwYi5piPc11xhCCv7WK3fxL2ZScCs/dSZYwPGCDz8G0iSkSZf/p4cWL6FHEdI1A= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, 24 Jan 2024 18:31:34 +0100 Alexander Potapenko wrote: > Similarly to what's been done in commit ff444efbbb9be ("kmsan: allow I make that 85716a80c16d. > using __msan_instrument_asm_store() inside runtime"), it should be safe > to call kmsan_unpoison_memory() from within the runtime, as it does not > allocate memory or take locks. Remove the redundant runtime checks. > > This should fix false positives seen with CONFIG_DEBUG_LIST=y when > the non-instrumented lib/stackdepot.c failed to unpoison the memory > chunks later checked by the instrumented lib/list_debug.c > > Also replace the implementation of kmsan_unpoison_entry_regs() with > a call to kmsan_unpoison_memory(). > "false positives" sound unpleasant. Should this fix be backported into earlier kernels? And can we identify a suitable Fixes: target?