From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 30 Apr 2019 04:17:18 -0700 Sender: tip tree robot From: tip-bot for Nadav Amit Message-ID: In-Reply-To: <20190426001143.4983-5-namit@vmware.com> References: <20190426001143.4983-5-namit@vmware.com> Subject: [tip:x86/mm] x86/mm: Save debug registers when loading a temporary mm MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline To: linux-tip-commits@vger.kernel.org Cc: bp@alien8.de, tglx@linutronix.de, hpa@zytor.com, rick.p.edgecombe@intel.com, peterz@infradead.org, mingo@kernel.org, akpm@linux-foundation.org, will.deacon@arm.com, luto@kernel.org, ard.biesheuvel@linaro.org, deneen.t.dock@intel.com, linux-kernel@vger.kernel.org, namit@vmware.com, riel@surriel.com, kristen@linux.intel.com, linux_dti@icloud.com, torvalds@linux-foundation.org, dave.hansen@linux.intel.com, kernel-hardening@lists.openwall.com List-ID: Commit-ID: d97080ebed7811a53c931032a284166ee46b9565 Gitweb: https://git.kernel.org/tip/d97080ebed7811a53c931032a284166ee46b9565 Author: Nadav Amit AuthorDate: Thu, 25 Apr 2019 17:11:24 -0700 Committer: Ingo Molnar CommitDate: Tue, 30 Apr 2019 12:37:50 +0200 x86/mm: Save debug registers when loading a temporary mm Prevent user watchpoints from mistakenly firing while the temporary mm is being used. As the addresses of the temporary mm might overlap those of the user-process, this is necessary to prevent wrong signals or worse things from happening. Signed-off-by: Nadav Amit Signed-off-by: Rick Edgecombe Signed-off-by: Peter Zijlstra (Intel) Cc: Cc: Cc: Cc: Cc: Cc: Cc: Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Dave Hansen Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Rik van Riel Cc: Thomas Gleixner Link: https://lkml.kernel.org/r/20190426001143.4983-5-namit@vmware.com Signed-off-by: Ingo Molnar --- arch/x86/include/asm/mmu_context.h | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h index 24dc3b810970..93dff1963337 100644 --- a/arch/x86/include/asm/mmu_context.h +++ b/arch/x86/include/asm/mmu_context.h @@ -13,6 +13,7 @@ #include #include #include +#include extern atomic64_t last_mm_ctx_id; @@ -380,6 +381,21 @@ static inline temp_mm_state_t use_temporary_mm(struct mm_struct *mm) lockdep_assert_irqs_disabled(); temp_state.mm = this_cpu_read(cpu_tlbstate.loaded_mm); switch_mm_irqs_off(NULL, mm, current); + + /* + * If breakpoints are enabled, disable them while the temporary mm is + * used. Userspace might set up watchpoints on addresses that are used + * in the temporary mm, which would lead to wrong signals being sent or + * crashes. + * + * Note that breakpoints are not disabled selectively, which also causes + * kernel breakpoints (e.g., perf's) to be disabled. This might be + * undesirable, but still seems reasonable as the code that runs in the + * temporary mm should be short. + */ + if (hw_breakpoint_active()) + hw_breakpoint_disable(); + return temp_state; } @@ -387,6 +403,13 @@ static inline void unuse_temporary_mm(temp_mm_state_t prev_state) { lockdep_assert_irqs_disabled(); switch_mm_irqs_off(NULL, prev_state.mm, current); + + /* + * Restore the breakpoints if they were disabled before the temporary mm + * was loaded. + */ + if (hw_breakpoint_active()) + hw_breakpoint_restore(); } #endif /* _ASM_X86_MMU_CONTEXT_H */