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04 Apr 2025 06:17:18 -0700 From: Maciej Wieczor-Retman To: hpa@zytor.com, hch@infradead.org, nick.desaulniers+lkml@gmail.com, kuan-ying.lee@canonical.com, masahiroy@kernel.org, samuel.holland@sifive.com, mingo@redhat.com, corbet@lwn.net, ryabinin.a.a@gmail.com, guoweikang.kernel@gmail.com, jpoimboe@kernel.org, ardb@kernel.org, vincenzo.frascino@arm.com, glider@google.com, kirill.shutemov@linux.intel.com, apopple@nvidia.com, samitolvanen@google.com, maciej.wieczor-retman@intel.com, kaleshsingh@google.com, jgross@suse.com, andreyknvl@gmail.com, scott@os.amperecomputing.com, tony.luck@intel.com, dvyukov@google.com, pasha.tatashin@soleen.com, ziy@nvidia.com, broonie@kernel.org, gatlin.newhouse@gmail.com, jackmanb@google.com, wangkefeng.wang@huawei.com, thiago.bauermann@linaro.org, tglx@linutronix.de, kees@kernel.org, akpm@linux-foundation.org, jason.andryuk@amd.com, snovitoll@gmail.com, xin@zytor.com, jan.kiszka@siemens.com, bp@alien8.de, rppt@kernel.org, peterz@infradead.org, pankaj.gupta@amd.com, thuth@redhat.com, andriy.shevchenko@linux.intel.com, joel.granados@kernel.org, kbingham@kernel.org, nicolas@fjasle.eu, mark.rutland@arm.com, surenb@google.com, catalin.marinas@arm.com, morbo@google.com, justinstitt@google.com, ubizjak@gmail.com, jhubbard@nvidia.com, urezki@gmail.com, dave.hansen@linux.intel.com, bhe@redhat.com, luto@kernel.org, baohua@kernel.org, nathan@kernel.org, will@kernel.org, brgerst@gmail.com Cc: llvm@lists.linux.dev, linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, x86@kernel.org Subject: [PATCH v3 11/14] x86: Handle int3 for inline KASAN reports Date: Fri, 4 Apr 2025 15:14:15 +0200 Message-ID: <012c84049b853d6853a7d6c887ce0c2323bcd80a.1743772053.git.maciej.wieczor-retman@intel.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kbuild@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 When a tag mismatch happens in inline software tag-based KASAN on x86 an int3 instruction is executed and needs proper handling. Call kasan_report() from the int3 handler and pass down the proper information from registers - RDI should contain the problematic address and RAX other metadata. Also early return from the int3 selftest if inline KASAN is enabled since it will cause a kernel panic otherwise. Signed-off-by: Maciej Wieczor-Retman --- Changelog v3: - Add this patch to the series. arch/x86/kernel/alternative.c | 3 ++ arch/x86/kernel/traps.c | 52 +++++++++++++++++++++++++++++++++++ 2 files changed, 55 insertions(+) diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index bf82c6f7d690..ba277a25b57f 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -1979,6 +1979,9 @@ static noinline void __init int3_selftest(void) }; unsigned int val = 0; + if (IS_ENABLED(CONFIG_KASAN_INLINE)) + return; + BUG_ON(register_die_notifier(&int3_exception_nb)); /* diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 9f88b8a78e50..32c81fc2d439 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -16,6 +16,7 @@ #include #include #include +#include #include #include #include @@ -849,6 +850,51 @@ DEFINE_IDTENTRY_ERRORCODE(exc_general_protection) cond_local_irq_disable(regs); } +#ifdef CONFIG_KASAN_SW_TAGS + +#define KASAN_RAX_RECOVER 0x20 +#define KASAN_RAX_WRITE 0x10 +#define KASAN_RAX_SIZE_MASK 0x0f +#define KASAN_RAX_SIZE(rax) (1 << ((rax) & KASAN_RAX_SIZE_MASK)) + +static bool kasan_handler(struct pt_regs *regs) +{ + int metadata = regs->ax; + u64 addr = regs->di; + u64 pc = regs->ip; + bool recover = metadata & KASAN_RAX_RECOVER; + bool write = metadata & KASAN_RAX_WRITE; + size_t size = KASAN_RAX_SIZE(metadata); + + if (!IS_ENABLED(CONFIG_KASAN_INLINE)) + return false; + + if (user_mode(regs)) + return false; + + kasan_report((void *)addr, size, write, pc); + + /* + * The instrumentation allows to control whether we can proceed after + * a crash was detected. This is done by passing the -recover flag to + * the compiler. Disabling recovery allows to generate more compact + * code. + * + * Unfortunately disabling recovery doesn't work for the kernel right + * now. KASAN reporting is disabled in some contexts (for example when + * the allocator accesses slab object metadata; this is controlled by + * current->kasan_depth). All these accesses are detected by the tool, + * even though the reports for them are not printed. + * + * This is something that might be fixed at some point in the future. + */ + if (!recover) + die("Oops - KASAN", regs, 0); + return true; +} + +#endif + static bool do_int3(struct pt_regs *regs) { int res; @@ -863,6 +909,12 @@ static bool do_int3(struct pt_regs *regs) if (kprobe_int3_handler(regs)) return true; #endif + +#ifdef CONFIG_KASAN_SW_TAGS + if (kasan_handler(regs)) + return true; +#endif + res = notify_die(DIE_INT3, "int3", regs, 0, X86_TRAP_BP, SIGTRAP); return res == NOTIFY_STOP;