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X-CSE-ConnectionGUID: lgcGYhSRRgi3QWzfFPE5jQ== X-CSE-MsgGUID: TDZ/17PCSu6YY8JA4TTopQ== X-IronPort-AV: E=McAfee;i="6800,10657,11533"; a="68971106" X-IronPort-AV: E=Sophos;i="6.18,214,1751266800"; d="scan'208";a="68971106" Received: from fmviesa008.fm.intel.com ([10.60.135.148]) by fmvoesa105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2025 13:31:11 -0700 X-CSE-ConnectionGUID: MQA+TzInQqevwz5W19OOTw== X-CSE-MsgGUID: GAgjeP88RDmDgTZRoDSocQ== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.18,214,1751266800"; d="scan'208";a="169780957" Received: from bergbenj-mobl1.ger.corp.intel.com (HELO wieczorr-mobl1.intel.com) ([10.245.245.6]) by fmviesa008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Aug 2025 13:30:49 -0700 From: Maciej Wieczor-Retman To: sohil.mehta@intel.com, baohua@kernel.org, david@redhat.com, kbingham@kernel.org, weixugc@google.com, Liam.Howlett@oracle.com, alexandre.chartre@oracle.com, kas@kernel.org, mark.rutland@arm.com, trintaeoitogc@gmail.com, axelrasmussen@google.com, yuanchu@google.com, joey.gouly@arm.com, samitolvanen@google.com, joel.granados@kernel.org, graf@amazon.com, vincenzo.frascino@arm.com, kees@kernel.org, ardb@kernel.org, thiago.bauermann@linaro.org, glider@google.com, thuth@redhat.com, kuan-ying.lee@canonical.com, pasha.tatashin@soleen.com, nick.desaulniers+lkml@gmail.com, vbabka@suse.cz, kaleshsingh@google.com, justinstitt@google.com, catalin.marinas@arm.com, alexander.shishkin@linux.intel.com, samuel.holland@sifive.com, dave.hansen@linux.intel.com, corbet@lwn.net, xin@zytor.com, dvyukov@google.com, tglx@linutronix.de, scott@os.amperecomputing.com, jason.andryuk@amd.com, morbo@google.com, nathan@kernel.org, lorenzo.stoakes@oracle.com, mingo@redhat.com, brgerst@gmail.com, kristina.martsenko@arm.com, bigeasy@linutronix.de, luto@kernel.org, jgross@suse.com, jpoimboe@kernel.org, urezki@gmail.com, mhocko@suse.com, ada.coupriediaz@arm.com, hpa@zytor.com, maciej.wieczor-retman@intel.com, leitao@debian.org, peterz@infradead.org, wangkefeng.wang@huawei.com, surenb@google.com, ziy@nvidia.com, smostafa@google.com, ryabinin.a.a@gmail.com, ubizjak@gmail.com, jbohac@suse.cz, broonie@kernel.org, akpm@linux-foundation.org, guoweikang.kernel@gmail.com, rppt@kernel.org, pcc@google.com, jan.kiszka@siemens.com, nicolas.schier@linux.dev, will@kernel.org, andreyknvl@gmail.com, jhubbard@nvidia.com, bp@alien8.de Cc: x86@kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev, linux-kbuild@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH v5 16/19] kasan: x86: Logical bit shift for kasan_mem_to_shadow Date: Mon, 25 Aug 2025 22:24:41 +0200 Message-ID: <169510f5490cba60916b144398543a489c31e2c1.1756151769.git.maciej.wieczor-retman@intel.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: E991514000F X-Stat-Signature: n99dikh7aeg7ixjazsoxdq44jjyaggkw X-Rspam-User: X-HE-Tag: 1756153872-381798 X-HE-Meta: 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 7f1OI+ZT ilN+WRdVyHGJixSPGqwa9aPvI/j3nBRfwDHXIjzha25ajzBjGOdQzPDKaCagXdrA+skcAaIgxVMdibhIk48IMi7crSslukOamCl0IWapF+BABjSymIC0o+MddH0vQKeIIqab+Dz/ukXFwVDQhf1IIGgcak+H387NPYk74McicT95/mIxaNteYPD7n61P/Srs95RMmR2R87rNemSZJEiCwiTVM6Xm49+69j7eBxxPFNMOnA+6enFK2QNo9bJ97ZsP9DYMsubkfCt4k5v4oWxZMLV5d/3wP9pU28OzkAxnuycVr/BefVh01OPkEDSFVngF9qr5NSS56tF6j35r0e7cRYdgB3Q== 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: While generally tag-based KASAN adopts an arithemitc bit shift to convert a memory address to a shadow memory address, it doesn't work for all cases on x86. Testing different shadow memory offsets proved that either 4 or 5 level paging didn't work correctly or inline mode ran into issues. Thus the best working scheme is the logical bit shift and non-canonical shadow offset that x86 uses for generic KASAN, of course adjusted for the increased granularity from 8 to 16 bytes. Add an arch specific implementation of kasan_mem_to_shadow() that uses the logical bit shift. The non-canonical hook tries to calculate whether an address came from kasan_mem_to_shadow(). First it checks whether this address fits into the legal set of values possible to output from the mem to shadow function. Tie both generic and tag-based x86 KASAN modes to the address range check associated with generic KASAN. Signed-off-by: Maciej Wieczor-Retman --- Changelog v4: - Add this patch to the series. arch/x86/include/asm/kasan.h | 8 ++++++++ mm/kasan/report.c | 5 +++-- 2 files changed, 11 insertions(+), 2 deletions(-) diff --git a/arch/x86/include/asm/kasan.h b/arch/x86/include/asm/kasan.h index 5bf38bb836e1..f3e34a9754d2 100644 --- a/arch/x86/include/asm/kasan.h +++ b/arch/x86/include/asm/kasan.h @@ -53,6 +53,14 @@ #ifdef CONFIG_KASAN_SW_TAGS +static inline void *__kasan_mem_to_shadow(const void *addr) +{ + return (void *)((unsigned long)addr >> KASAN_SHADOW_SCALE_SHIFT) + + KASAN_SHADOW_OFFSET; +} + +#define kasan_mem_to_shadow(addr) __kasan_mem_to_shadow(addr) + #define __tag_shifted(tag) FIELD_PREP(GENMASK_ULL(60, 57), tag) #define __tag_reset(addr) (sign_extend64((u64)(addr), 56)) #define __tag_get(addr) ((u8)FIELD_GET(GENMASK_ULL(60, 57), (u64)addr)) diff --git a/mm/kasan/report.c b/mm/kasan/report.c index 9e830639e1b2..ee440ed1ecd3 100644 --- a/mm/kasan/report.c +++ b/mm/kasan/report.c @@ -648,13 +648,14 @@ void kasan_non_canonical_hook(unsigned long addr) const char *bug_type; /* - * For Generic KASAN, kasan_mem_to_shadow() uses the logical right shift + * For Generic KASAN and Software Tag-Based mode on the x86 + * architecture, kasan_mem_to_shadow() uses the logical right shift * and never overflows with the chosen KASAN_SHADOW_OFFSET values (on * both x86 and arm64). Thus, the possible shadow addresses (even for * bogus pointers) belong to a single contiguous region that is the * result of kasan_mem_to_shadow() applied to the whole address space. */ - if (IS_ENABLED(CONFIG_KASAN_GENERIC)) { + if (IS_ENABLED(CONFIG_KASAN_GENERIC) || IS_ENABLED(CONFIG_X86_64)) { if (addr < (unsigned long)kasan_mem_to_shadow((void *)(0UL)) || addr > (unsigned long)kasan_mem_to_shadow((void *)(~0UL))) return; -- 2.50.1