From: Andy Lutomirski <luto@kernel.org> To: x86@kernel.org, linux-kernel@vger.kernel.org Cc: linux-arch@vger.kernel.org, Borislav Petkov <bp@alien8.de>, Nadav Amit <nadav.amit@gmail.com>, Kees Cook <keescook@chromium.org>, Brian Gerst <brgerst@gmail.com>, "kernel-hardening@lists.openwall.com" <kernel-hardening@lists.openwall.com>, Linus Torvalds <torvalds@linux-foundation.org>, Josh Poimboeuf <jpoimboe@redhat.com>, Jann Horn <jann@thejh.net>, Heiko Carstens <heiko.carstens@de.ibm.com>, Andy Lutomirski <luto@kernel.org> Subject: [PATCH v2 08/13] x86/dumpstack: When OOPSing, rewind the stack before do_exit Date: Fri, 17 Jun 2016 13:00:44 -0700 [thread overview] Message-ID: <b22badbe9ebcb6ad283b243f851c1b7d33d5bb2a.1466192946.git.luto@kernel.org> (raw) In-Reply-To: <cover.1466192946.git.luto@kernel.org> In-Reply-To: <cover.1466192946.git.luto@kernel.org> If we call do_exit with a clean stack, we greatly reduce the risk of recursive oopses due to stack overflow in do_exit, and we allow do_exit to work even if we OOPS from an IST stack. The latter gives us a much better chance of surviving long enough after we detect a stack overflow to write out our logs. I intentionally separated this from the preceding patch that disables do_exit-on-OOPS on IST stacks. This way, if we need to revert this patch, we still end up in an acceptable state wrt stack overflow handling. Signed-off-by: Andy Lutomirski <luto@kernel.org> --- arch/x86/entry/entry_32.S | 11 +++++++++++ arch/x86/entry/entry_64.S | 11 +++++++++++ arch/x86/kernel/dumpstack.c | 13 +++++++++---- 3 files changed, 31 insertions(+), 4 deletions(-) diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index 983e5d3a0d27..0b56666e6039 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -1153,3 +1153,14 @@ ENTRY(async_page_fault) jmp error_code END(async_page_fault) #endif + +ENTRY(rewind_stack_do_exit) + /* Prevent any naive code from trying to unwind to our caller. */ + xorl %ebp, %ebp + + movl PER_CPU_VAR(cpu_current_top_of_stack), %esi + leal -TOP_OF_KERNEL_STACK_PADDING-PTREGS_SIZE(%esi), %esp + + call do_exit +1: jmp 1b +END(rewind_stack_do_exit) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 9ee0da1807ed..b846875aeea6 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -1423,3 +1423,14 @@ ENTRY(ignore_sysret) mov $-ENOSYS, %eax sysret END(ignore_sysret) + +ENTRY(rewind_stack_do_exit) + /* Prevent any naive code from trying to unwind to our caller. */ + xorl %ebp, %ebp + + movq PER_CPU_VAR(cpu_current_top_of_stack), %rax + leaq -TOP_OF_KERNEL_STACK_PADDING-PTREGS_SIZE(%rax), %rsp + + call do_exit +1: jmp 1b +END(rewind_stack_do_exit) diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c index 36effb39c9c9..d4d085e27d04 100644 --- a/arch/x86/kernel/dumpstack.c +++ b/arch/x86/kernel/dumpstack.c @@ -228,6 +228,8 @@ unsigned long oops_begin(void) EXPORT_SYMBOL_GPL(oops_begin); NOKPROBE_SYMBOL(oops_begin); +extern void __noreturn rewind_stack_do_exit(int signr); + void oops_end(unsigned long flags, struct pt_regs *regs, int signr) { if (regs && kexec_should_crash(current)) @@ -247,12 +249,15 @@ void oops_end(unsigned long flags, struct pt_regs *regs, int signr) return; if (in_interrupt()) panic("Fatal exception in interrupt"); - if (((current_stack_pointer() ^ (current_top_of_stack() - 1)) - & ~(THREAD_SIZE - 1)) != 0) - panic("Fatal exception on special stack"); if (panic_on_oops) panic("Fatal exception"); - do_exit(signr); + + /* + * We're not going to return, but we might be on an IST stack or + * have very little stack space left. Rewind the stack and kill + * the task. + */ + rewind_stack_do_exit(signr); } NOKPROBE_SYMBOL(oops_end); -- 2.5.5
WARNING: multiple messages have this Message-ID (diff)
From: Andy Lutomirski <luto@kernel.org> To: x86@kernel.org, linux-kernel@vger.kernel.org Cc: linux-arch@vger.kernel.org, Borislav Petkov <bp@alien8.de>, Nadav Amit <nadav.amit@gmail.com>, Kees Cook <keescook@chromium.org>, Brian Gerst <brgerst@gmail.com>, "kernel-hardening@lists.openwall.com" <kernel-hardening@lists.openwall.com>, Linus Torvalds <torvalds@linux-foundation.org>, Josh Poimboeuf <jpoimboe@redhat.com>, Jann Horn <jann@thejh.net>, Heiko Carstens <heiko.carstens@de.ibm.com>, Andy Lutomirski <luto@kernel.org> Subject: [kernel-hardening] [PATCH v2 08/13] x86/dumpstack: When OOPSing, rewind the stack before do_exit Date: Fri, 17 Jun 2016 13:00:44 -0700 [thread overview] Message-ID: <b22badbe9ebcb6ad283b243f851c1b7d33d5bb2a.1466192946.git.luto@kernel.org> (raw) In-Reply-To: <cover.1466192946.git.luto@kernel.org> In-Reply-To: <cover.1466192946.git.luto@kernel.org> If we call do_exit with a clean stack, we greatly reduce the risk of recursive oopses due to stack overflow in do_exit, and we allow do_exit to work even if we OOPS from an IST stack. The latter gives us a much better chance of surviving long enough after we detect a stack overflow to write out our logs. I intentionally separated this from the preceding patch that disables do_exit-on-OOPS on IST stacks. This way, if we need to revert this patch, we still end up in an acceptable state wrt stack overflow handling. Signed-off-by: Andy Lutomirski <luto@kernel.org> --- arch/x86/entry/entry_32.S | 11 +++++++++++ arch/x86/entry/entry_64.S | 11 +++++++++++ arch/x86/kernel/dumpstack.c | 13 +++++++++---- 3 files changed, 31 insertions(+), 4 deletions(-) diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index 983e5d3a0d27..0b56666e6039 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -1153,3 +1153,14 @@ ENTRY(async_page_fault) jmp error_code END(async_page_fault) #endif + +ENTRY(rewind_stack_do_exit) + /* Prevent any naive code from trying to unwind to our caller. */ + xorl %ebp, %ebp + + movl PER_CPU_VAR(cpu_current_top_of_stack), %esi + leal -TOP_OF_KERNEL_STACK_PADDING-PTREGS_SIZE(%esi), %esp + + call do_exit +1: jmp 1b +END(rewind_stack_do_exit) diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 9ee0da1807ed..b846875aeea6 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -1423,3 +1423,14 @@ ENTRY(ignore_sysret) mov $-ENOSYS, %eax sysret END(ignore_sysret) + +ENTRY(rewind_stack_do_exit) + /* Prevent any naive code from trying to unwind to our caller. */ + xorl %ebp, %ebp + + movq PER_CPU_VAR(cpu_current_top_of_stack), %rax + leaq -TOP_OF_KERNEL_STACK_PADDING-PTREGS_SIZE(%rax), %rsp + + call do_exit +1: jmp 1b +END(rewind_stack_do_exit) diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c index 36effb39c9c9..d4d085e27d04 100644 --- a/arch/x86/kernel/dumpstack.c +++ b/arch/x86/kernel/dumpstack.c @@ -228,6 +228,8 @@ unsigned long oops_begin(void) EXPORT_SYMBOL_GPL(oops_begin); NOKPROBE_SYMBOL(oops_begin); +extern void __noreturn rewind_stack_do_exit(int signr); + void oops_end(unsigned long flags, struct pt_regs *regs, int signr) { if (regs && kexec_should_crash(current)) @@ -247,12 +249,15 @@ void oops_end(unsigned long flags, struct pt_regs *regs, int signr) return; if (in_interrupt()) panic("Fatal exception in interrupt"); - if (((current_stack_pointer() ^ (current_top_of_stack() - 1)) - & ~(THREAD_SIZE - 1)) != 0) - panic("Fatal exception on special stack"); if (panic_on_oops) panic("Fatal exception"); - do_exit(signr); + + /* + * We're not going to return, but we might be on an IST stack or + * have very little stack space left. Rewind the stack and kill + * the task. + */ + rewind_stack_do_exit(signr); } NOKPROBE_SYMBOL(oops_end); -- 2.5.5
next prev parent reply other threads:[~2016-06-17 20:01 UTC|newest] Thread overview: 93+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-06-17 20:00 [PATCH v2 00/13] Virtually mapped stacks with guard pages (x86, core) Andy Lutomirski 2016-06-17 20:00 ` [kernel-hardening] " Andy Lutomirski 2016-06-17 20:00 ` Andy Lutomirski 2016-06-17 20:00 ` [PATCH v2 01/13] x86/mm/hotplug: Don't remove PGD entries in remove_pagetable() Andy Lutomirski 2016-06-17 20:00 ` [kernel-hardening] " Andy Lutomirski 2016-06-17 20:00 ` Andy Lutomirski 2016-06-17 20:00 ` Andy Lutomirski 2016-06-17 20:00 ` [PATCH v2 02/13] x86/cpa: In populate_pgd, don't set the pgd entry until it's populated Andy Lutomirski 2016-06-17 20:00 ` [kernel-hardening] " Andy Lutomirski 2016-06-17 20:00 ` Andy Lutomirski 2016-06-17 20:00 ` [PATCH v2 03/13] x86/cpa: Warn if kernel_unmap_pages_in_pgd is used inappropriately Andy Lutomirski 2016-06-17 20:00 ` [kernel-hardening] " Andy Lutomirski 2016-06-17 20:00 ` Andy Lutomirski 2016-06-17 20:30 ` Borislav Petkov 2016-06-17 20:30 ` [kernel-hardening] " Borislav Petkov 2016-06-17 20:30 ` Borislav Petkov 2016-06-18 10:29 ` Andy Lutomirski 2016-06-18 10:29 ` [kernel-hardening] " Andy Lutomirski 2016-06-18 10:29 ` Andy Lutomirski 2016-06-18 10:37 ` Borislav Petkov 2016-06-18 10:37 ` [kernel-hardening] " Borislav Petkov 2016-06-18 10:37 ` Borislav Petkov 2016-06-17 20:00 ` [PATCH v2 04/13] mm: Track NR_KERNEL_STACK in KiB instead of number of stacks Andy Lutomirski 2016-06-17 20:00 ` [kernel-hardening] " Andy Lutomirski 2016-06-17 20:00 ` Andy Lutomirski 2016-06-17 20:00 ` Andy Lutomirski 2016-06-20 13:16 ` Michal Hocko 2016-06-20 13:16 ` [kernel-hardening] " Michal Hocko 2016-06-20 13:16 ` Michal Hocko 2016-06-20 13:16 ` Michal Hocko 2016-06-17 20:00 ` [PATCH v2 05/13] mm: Move memcg stack accounting to account_kernel_stack Andy Lutomirski 2016-06-17 20:00 ` [kernel-hardening] " Andy Lutomirski 2016-06-17 20:00 ` Andy Lutomirski 2016-06-17 20:00 ` Andy Lutomirski 2016-06-17 20:55 ` Josh Poimboeuf 2016-06-17 20:55 ` [kernel-hardening] " Josh Poimboeuf 2016-06-17 20:55 ` Josh Poimboeuf 2016-06-17 20:55 ` Josh Poimboeuf 2016-06-17 22:18 ` Andy Lutomirski 2016-06-17 22:18 ` [kernel-hardening] " Andy Lutomirski 2016-06-17 22:18 ` Andy Lutomirski 2016-06-17 22:18 ` Andy Lutomirski 2016-06-20 13:02 ` Michal Hocko 2016-06-20 13:02 ` [kernel-hardening] " Michal Hocko 2016-06-20 13:02 ` Michal Hocko 2016-06-20 13:02 ` Michal Hocko 2016-06-20 16:05 ` Andy Lutomirski 2016-06-20 16:05 ` [kernel-hardening] " Andy Lutomirski 2016-06-20 16:05 ` Andy Lutomirski 2016-06-20 16:05 ` Andy Lutomirski 2016-06-17 20:00 ` [PATCH v2 06/13] fork: Add generic vmalloced stack support Andy Lutomirski 2016-06-17 20:00 ` [kernel-hardening] " Andy Lutomirski 2016-06-17 20:00 ` Andy Lutomirski 2016-06-17 20:57 ` Josh Poimboeuf 2016-06-17 20:57 ` [kernel-hardening] " Josh Poimboeuf 2016-06-17 20:57 ` Josh Poimboeuf 2016-06-17 22:18 ` Andy Lutomirski 2016-06-17 22:18 ` [kernel-hardening] " Andy Lutomirski 2016-06-17 22:18 ` Andy Lutomirski 2016-06-20 13:36 ` Michal Hocko 2016-06-20 13:36 ` [kernel-hardening] " Michal Hocko 2016-06-20 13:36 ` Michal Hocko 2016-06-20 13:36 ` Michal Hocko 2016-06-20 16:13 ` Andy Lutomirski 2016-06-20 16:13 ` [kernel-hardening] " Andy Lutomirski 2016-06-20 16:13 ` Andy Lutomirski 2016-06-21 8:46 ` Michal Hocko 2016-06-21 8:46 ` [kernel-hardening] " Michal Hocko 2016-06-21 8:46 ` Michal Hocko 2016-06-21 17:01 ` Andy Lutomirski 2016-06-21 17:01 ` [kernel-hardening] " Andy Lutomirski 2016-06-21 17:01 ` Andy Lutomirski 2016-06-17 20:00 ` [PATCH v2 07/13] x86/die: Don't try to recover from an OOPS on a non-default stack Andy Lutomirski 2016-06-17 20:00 ` [kernel-hardening] " Andy Lutomirski 2016-06-17 20:00 ` Andy Lutomirski 2016-06-17 20:00 ` Andy Lutomirski [this message] 2016-06-17 20:00 ` [kernel-hardening] [PATCH v2 08/13] x86/dumpstack: When OOPSing, rewind the stack before do_exit Andy Lutomirski 2016-06-17 20:00 ` Andy Lutomirski 2016-06-17 20:00 ` [PATCH v2 09/13] x86/dumpstack: When dumping stack bytes due to OOPS, start with regs->sp Andy Lutomirski 2016-06-17 20:00 ` [kernel-hardening] " Andy Lutomirski 2016-06-17 20:00 ` Andy Lutomirski 2016-06-17 20:00 ` [PATCH v2 10/13] x86/dumpstack: Try harder to get a call trace on stack overflow Andy Lutomirski 2016-06-17 20:00 ` [kernel-hardening] " Andy Lutomirski 2016-06-17 20:00 ` Andy Lutomirski 2016-06-17 20:00 ` [PATCH v2 11/13] x86/dumpstack/64: Handle faults when printing the "Stack:" part of an OOPS Andy Lutomirski 2016-06-17 20:00 ` [kernel-hardening] " Andy Lutomirski 2016-06-17 20:00 ` Andy Lutomirski 2016-06-17 20:00 ` [PATCH v2 12/13] x86/mm/64: Enable vmapped stacks Andy Lutomirski 2016-06-17 20:00 ` [kernel-hardening] " Andy Lutomirski 2016-06-17 20:00 ` Andy Lutomirski 2016-06-17 20:00 ` [PATCH v2 13/13] x86/mm: Improve stack-overflow #PF handling Andy Lutomirski 2016-06-17 20:00 ` [kernel-hardening] " Andy Lutomirski 2016-06-17 20:00 ` Andy Lutomirski
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