| Message ID | 20240529022043.3661757-1-gatlin.newhouse@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | x86/traps: Enable UBSAN traps on x86 | expand |
On Wed, 29 May 2024 at 04:20, Gatlin Newhouse <gatlin.newhouse@gmail.com> wrote: [...] > if (regs->flags & X86_EFLAGS_IF) > raw_local_irq_enable(); > - if (report_bug(regs->ip, regs) == BUG_TRAP_TYPE_WARN || > - handle_cfi_failure(regs) == BUG_TRAP_TYPE_WARN) { > - regs->ip += LEN_UD2; > - handled = true; > + > + if (insn == INSN_UD2) { > + if (report_bug(regs->ip, regs) == BUG_TRAP_TYPE_WARN || > + handle_cfi_failure(regs) == BUG_TRAP_TYPE_WARN) { > + regs->ip += LEN_UD2; > + handled = true; > + } > + } else { > + if (handle_ubsan_failure(regs, insn) == BUG_TRAP_TYPE_WARN) { handle_ubsan_failure currently only returns BUG_TRAP_TYPE_NONE? > + if (insn == INSN_REX) > + regs->ip += LEN_REX; > + regs->ip += LEN_UD1; > + handled = true; > + } > } > if (regs->flags & X86_EFLAGS_IF) > raw_local_irq_disable(); > diff --git a/arch/x86/kernel/ubsan.c b/arch/x86/kernel/ubsan.c > new file mode 100644 > index 000000000000..6cae11f4fe23 > --- /dev/null > +++ b/arch/x86/kernel/ubsan.c > @@ -0,0 +1,32 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Clang Undefined Behavior Sanitizer trap mode support. > + */ > +#include <linux/bug.h> > +#include <linux/string.h> > +#include <linux/printk.h> > +#include <linux/ubsan.h> > +#include <asm/ptrace.h> > +#include <asm/ubsan.h> > + > +/* > + * Checks for the information embedded in the UD1 trap instruction > + * for the UB Sanitizer in order to pass along debugging output. > + */ > +enum bug_trap_type handle_ubsan_failure(struct pt_regs *regs, int insn) > +{ > + u32 type = 0; > + > + if (insn == INSN_REX) { > + type = (*(u16 *)(regs->ip + LEN_REX + LEN_UD1)); > + if ((type & 0xFF) == 0x40) > + type = (type >> 8) & 0xFF; > + } else { > + type = (*(u16 *)(regs->ip + LEN_UD1)); > + if ((type & 0xFF) == 0x40) > + type = (type >> 8) & 0xFF; > + } > + pr_crit("%s at %pS\n", report_ubsan_failure(regs, type), (void *)regs->ip); > + > + return BUG_TRAP_TYPE_NONE; > +} Shouldn't this return BUG_TRAP_TYPE_WARN?
On Wed, May 29, 2024 at 09:25:21AM UTC, Marco Elver wrote: > On Wed, 29 May 2024 at 04:20, Gatlin Newhouse <gatlin.newhouse@gmail.com> wrote: > [...] > > if (regs->flags & X86_EFLAGS_IF) > > raw_local_irq_enable(); > > - if (report_bug(regs->ip, regs) == BUG_TRAP_TYPE_WARN || > > - handle_cfi_failure(regs) == BUG_TRAP_TYPE_WARN) { > > - regs->ip += LEN_UD2; > > - handled = true; > > + > > + if (insn == INSN_UD2) { > > + if (report_bug(regs->ip, regs) == BUG_TRAP_TYPE_WARN || > > + handle_cfi_failure(regs) == BUG_TRAP_TYPE_WARN) { > > + regs->ip += LEN_UD2; > > + handled = true; > > + } > > + } else { > > + if (handle_ubsan_failure(regs, insn) == BUG_TRAP_TYPE_WARN) { > > handle_ubsan_failure currently only returns BUG_TRAP_TYPE_NONE? > > > + if (insn == INSN_REX) > > + regs->ip += LEN_REX; > > + regs->ip += LEN_UD1; > > + handled = true; > > + } > > } > > if (regs->flags & X86_EFLAGS_IF) > > raw_local_irq_disable(); > > diff --git a/arch/x86/kernel/ubsan.c b/arch/x86/kernel/ubsan.c > > new file mode 100644 > > index 000000000000..6cae11f4fe23 > > --- /dev/null > > +++ b/arch/x86/kernel/ubsan.c > > @@ -0,0 +1,32 @@ > > +// SPDX-License-Identifier: GPL-2.0 > > +/* > > + * Clang Undefined Behavior Sanitizer trap mode support. > > + */ > > +#include <linux/bug.h> > > +#include <linux/string.h> > > +#include <linux/printk.h> > > +#include <linux/ubsan.h> > > +#include <asm/ptrace.h> > > +#include <asm/ubsan.h> > > + > > +/* > > + * Checks for the information embedded in the UD1 trap instruction > > + * for the UB Sanitizer in order to pass along debugging output. > > + */ > > +enum bug_trap_type handle_ubsan_failure(struct pt_regs *regs, int insn) > > +{ > > + u32 type = 0; > > + > > + if (insn == INSN_REX) { > > + type = (*(u16 *)(regs->ip + LEN_REX + LEN_UD1)); > > + if ((type & 0xFF) == 0x40) > > + type = (type >> 8) & 0xFF; > > + } else { > > + type = (*(u16 *)(regs->ip + LEN_UD1)); > > + if ((type & 0xFF) == 0x40) > > + type = (type >> 8) & 0xFF; > > + } > > + pr_crit("%s at %pS\n", report_ubsan_failure(regs, type), (void *)regs->ip); > > + > > + return BUG_TRAP_TYPE_NONE; > > +} > > Shouldn't this return BUG_TRAP_TYPE_WARN? So as far as I understand, UBSAN trap mode never warns. Perhaps it does on arm64, although it calls die() so I am unsure. Maybe the condition in handle_bug() should be rewritten in the case of UBSAN ud1s? Do you have any suggestions?
On Wed, 29 May 2024 at 20:17, Gatlin Newhouse <gatlin.newhouse@gmail.com> wrote: > > On Wed, May 29, 2024 at 09:25:21AM UTC, Marco Elver wrote: > > On Wed, 29 May 2024 at 04:20, Gatlin Newhouse <gatlin.newhouse@gmail.com> wrote: > > [...] > > > if (regs->flags & X86_EFLAGS_IF) > > > raw_local_irq_enable(); > > > - if (report_bug(regs->ip, regs) == BUG_TRAP_TYPE_WARN || > > > - handle_cfi_failure(regs) == BUG_TRAP_TYPE_WARN) { > > > - regs->ip += LEN_UD2; > > > - handled = true; > > > + > > > + if (insn == INSN_UD2) { > > > + if (report_bug(regs->ip, regs) == BUG_TRAP_TYPE_WARN || > > > + handle_cfi_failure(regs) == BUG_TRAP_TYPE_WARN) { > > > + regs->ip += LEN_UD2; > > > + handled = true; > > > + } > > > + } else { > > > + if (handle_ubsan_failure(regs, insn) == BUG_TRAP_TYPE_WARN) { > > > > handle_ubsan_failure currently only returns BUG_TRAP_TYPE_NONE? > > > > > + if (insn == INSN_REX) > > > + regs->ip += LEN_REX; > > > + regs->ip += LEN_UD1; > > > + handled = true; > > > + } > > > } > > > if (regs->flags & X86_EFLAGS_IF) > > > raw_local_irq_disable(); > > > diff --git a/arch/x86/kernel/ubsan.c b/arch/x86/kernel/ubsan.c > > > new file mode 100644 > > > index 000000000000..6cae11f4fe23 > > > --- /dev/null > > > +++ b/arch/x86/kernel/ubsan.c > > > @@ -0,0 +1,32 @@ > > > +// SPDX-License-Identifier: GPL-2.0 > > > +/* > > > + * Clang Undefined Behavior Sanitizer trap mode support. > > > + */ > > > +#include <linux/bug.h> > > > +#include <linux/string.h> > > > +#include <linux/printk.h> > > > +#include <linux/ubsan.h> > > > +#include <asm/ptrace.h> > > > +#include <asm/ubsan.h> > > > + > > > +/* > > > + * Checks for the information embedded in the UD1 trap instruction > > > + * for the UB Sanitizer in order to pass along debugging output. > > > + */ > > > +enum bug_trap_type handle_ubsan_failure(struct pt_regs *regs, int insn) > > > +{ > > > + u32 type = 0; > > > + > > > + if (insn == INSN_REX) { > > > + type = (*(u16 *)(regs->ip + LEN_REX + LEN_UD1)); > > > + if ((type & 0xFF) == 0x40) > > > + type = (type >> 8) & 0xFF; > > > + } else { > > > + type = (*(u16 *)(regs->ip + LEN_UD1)); > > > + if ((type & 0xFF) == 0x40) > > > + type = (type >> 8) & 0xFF; > > > + } > > > + pr_crit("%s at %pS\n", report_ubsan_failure(regs, type), (void *)regs->ip); > > > + > > > + return BUG_TRAP_TYPE_NONE; > > > +} > > > > Shouldn't this return BUG_TRAP_TYPE_WARN? > > So as far as I understand, UBSAN trap mode never warns. Perhaps it does on > arm64, although it calls die() so I am unsure. Maybe the condition in > handle_bug() should be rewritten in the case of UBSAN ud1s? Do you have any > suggestions? AFAIK on arm64 it's basically a kernel OOPS. The main thing I just wanted to point out though is that your newly added branch > if (handle_ubsan_failure(regs, insn) == BUG_TRAP_TYPE_WARN) { will never be taken, because I don't see where handle_ubsan_failure() returns BUG_TRAP_TYPE_WARN. That means 'handled' will be false, and the code in exc_invalid_op will proceed to call handle_invalid_op() which is probably not what you intended - i.e. it's definitely not BUG_TRAP_TYPE_NONE, but one of TYPE_WARN of TYPE_BUG. Did you test it and you got the behaviour you expected?
On Wed, May 29, 2024 at 08:30:20PM UTC, Marco Elver wrote: > On Wed, 29 May 2024 at 20:17, Gatlin Newhouse <gatlin.newhouse@gmail.com> wrote: > > > > On Wed, May 29, 2024 at 09:25:21AM UTC, Marco Elver wrote: > > > On Wed, 29 May 2024 at 04:20, Gatlin Newhouse <gatlin.newhouse@gmail.com> wrote: > > > [...] > > > > if (regs->flags & X86_EFLAGS_IF) > > > > raw_local_irq_enable(); > > > > - if (report_bug(regs->ip, regs) == BUG_TRAP_TYPE_WARN || > > > > - handle_cfi_failure(regs) == BUG_TRAP_TYPE_WARN) { > > > > - regs->ip += LEN_UD2; > > > > - handled = true; > > > > + > > > > + if (insn == INSN_UD2) { > > > > + if (report_bug(regs->ip, regs) == BUG_TRAP_TYPE_WARN || > > > > + handle_cfi_failure(regs) == BUG_TRAP_TYPE_WARN) { > > > > + regs->ip += LEN_UD2; > > > > + handled = true; > > > > + } > > > > + } else { > > > > + if (handle_ubsan_failure(regs, insn) == BUG_TRAP_TYPE_WARN) { > > > > > > handle_ubsan_failure currently only returns BUG_TRAP_TYPE_NONE? > > > > > > > + if (insn == INSN_REX) > > > > + regs->ip += LEN_REX; > > > > + regs->ip += LEN_UD1; > > > > + handled = true; > > > > + } > > > > } > > > > if (regs->flags & X86_EFLAGS_IF) > > > > raw_local_irq_disable(); > > > > diff --git a/arch/x86/kernel/ubsan.c b/arch/x86/kernel/ubsan.c > > > > new file mode 100644 > > > > index 000000000000..6cae11f4fe23 > > > > --- /dev/null > > > > +++ b/arch/x86/kernel/ubsan.c > > > > @@ -0,0 +1,32 @@ > > > > +// SPDX-License-Identifier: GPL-2.0 > > > > +/* > > > > + * Clang Undefined Behavior Sanitizer trap mode support. > > > > + */ > > > > +#include <linux/bug.h> > > > > +#include <linux/string.h> > > > > +#include <linux/printk.h> > > > > +#include <linux/ubsan.h> > > > > +#include <asm/ptrace.h> > > > > +#include <asm/ubsan.h> > > > > + > > > > +/* > > > > + * Checks for the information embedded in the UD1 trap instruction > > > > + * for the UB Sanitizer in order to pass along debugging output. > > > > + */ > > > > +enum bug_trap_type handle_ubsan_failure(struct pt_regs *regs, int insn) > > > > +{ > > > > + u32 type = 0; > > > > + > > > > + if (insn == INSN_REX) { > > > > + type = (*(u16 *)(regs->ip + LEN_REX + LEN_UD1)); > > > > + if ((type & 0xFF) == 0x40) > > > > + type = (type >> 8) & 0xFF; > > > > + } else { > > > > + type = (*(u16 *)(regs->ip + LEN_UD1)); > > > > + if ((type & 0xFF) == 0x40) > > > > + type = (type >> 8) & 0xFF; > > > > + } > > > > + pr_crit("%s at %pS\n", report_ubsan_failure(regs, type), (void *)regs->ip); > > > > + > > > > + return BUG_TRAP_TYPE_NONE; > > > > +} > > > > > > Shouldn't this return BUG_TRAP_TYPE_WARN? > > > > So as far as I understand, UBSAN trap mode never warns. Perhaps it does on > > arm64, although it calls die() so I am unsure. Maybe the condition in > > handle_bug() should be rewritten in the case of UBSAN ud1s? Do you have any > > suggestions? > > AFAIK on arm64 it's basically a kernel OOPS. > > The main thing I just wanted to point out though is that your newly added branch > > > if (handle_ubsan_failure(regs, insn) == BUG_TRAP_TYPE_WARN) { > > will never be taken, because I don't see where handle_ubsan_failure() > returns BUG_TRAP_TYPE_WARN. > Initially I wrote this with some symmetry to the KCFI checks nearby, but I was unsure if this would be considered handled or not. > > That means 'handled' will be false, and the code in exc_invalid_op > will proceed to call handle_invalid_op() which is probably not what > you intended - i.e. it's definitely not BUG_TRAP_TYPE_NONE, but one of > TYPE_WARN of TYPE_BUG. > This remains a question to me as to whether it should be considered handled or not. Which is why I'm happy to change this branch which is never taken to something else that still outputs the UBSAN type information before calling handle_invalid_op(). > > Did you test it and you got the behaviour you expected? > Testing with LKDTM provided the output I expected. The UBSAN type information along with file and offsets are output before an illegal op and trace.
On Wed, May 29, 2024 at 01:36:39PM -0700, Gatlin Newhouse wrote: > On Wed, May 29, 2024 at 08:30:20PM UTC, Marco Elver wrote: > > On Wed, 29 May 2024 at 20:17, Gatlin Newhouse <gatlin.newhouse@gmail.com> wrote: > > > > > > On Wed, May 29, 2024 at 09:25:21AM UTC, Marco Elver wrote: > > > > On Wed, 29 May 2024 at 04:20, Gatlin Newhouse <gatlin.newhouse@gmail.com> wrote: > > > > [...] > > > > > if (regs->flags & X86_EFLAGS_IF) > > > > > raw_local_irq_enable(); > > > > > - if (report_bug(regs->ip, regs) == BUG_TRAP_TYPE_WARN || > > > > > - handle_cfi_failure(regs) == BUG_TRAP_TYPE_WARN) { > > > > > - regs->ip += LEN_UD2; > > > > > - handled = true; > > > > > + > > > > > + if (insn == INSN_UD2) { > > > > > + if (report_bug(regs->ip, regs) == BUG_TRAP_TYPE_WARN || > > > > > + handle_cfi_failure(regs) == BUG_TRAP_TYPE_WARN) { > > > > > + regs->ip += LEN_UD2; > > > > > + handled = true; > > > > > + } > > > > > + } else { > > > > > + if (handle_ubsan_failure(regs, insn) == BUG_TRAP_TYPE_WARN) { > > > > > > > > handle_ubsan_failure currently only returns BUG_TRAP_TYPE_NONE? > > > > > > > > > + if (insn == INSN_REX) > > > > > + regs->ip += LEN_REX; > > > > > + regs->ip += LEN_UD1; > > > > > + handled = true; > > > > > + } > > > > > } > > > > > if (regs->flags & X86_EFLAGS_IF) > > > > > raw_local_irq_disable(); > > > > > diff --git a/arch/x86/kernel/ubsan.c b/arch/x86/kernel/ubsan.c > > > > > new file mode 100644 > > > > > index 000000000000..6cae11f4fe23 > > > > > --- /dev/null > > > > > +++ b/arch/x86/kernel/ubsan.c > > > > > @@ -0,0 +1,32 @@ > > > > > +// SPDX-License-Identifier: GPL-2.0 > > > > > +/* > > > > > + * Clang Undefined Behavior Sanitizer trap mode support. > > > > > + */ > > > > > +#include <linux/bug.h> > > > > > +#include <linux/string.h> > > > > > +#include <linux/printk.h> > > > > > +#include <linux/ubsan.h> > > > > > +#include <asm/ptrace.h> > > > > > +#include <asm/ubsan.h> > > > > > + > > > > > +/* > > > > > + * Checks for the information embedded in the UD1 trap instruction > > > > > + * for the UB Sanitizer in order to pass along debugging output. > > > > > + */ > > > > > +enum bug_trap_type handle_ubsan_failure(struct pt_regs *regs, int insn) > > > > > +{ > > > > > + u32 type = 0; > > > > > + > > > > > + if (insn == INSN_REX) { > > > > > + type = (*(u16 *)(regs->ip + LEN_REX + LEN_UD1)); > > > > > + if ((type & 0xFF) == 0x40) > > > > > + type = (type >> 8) & 0xFF; > > > > > + } else { > > > > > + type = (*(u16 *)(regs->ip + LEN_UD1)); > > > > > + if ((type & 0xFF) == 0x40) > > > > > + type = (type >> 8) & 0xFF; > > > > > + } > > > > > + pr_crit("%s at %pS\n", report_ubsan_failure(regs, type), (void *)regs->ip); > > > > > + > > > > > + return BUG_TRAP_TYPE_NONE; > > > > > +} > > > > > > > > Shouldn't this return BUG_TRAP_TYPE_WARN? > > > > > > So as far as I understand, UBSAN trap mode never warns. Perhaps it does on > > > arm64, although it calls die() so I am unsure. Maybe the condition in > > > handle_bug() should be rewritten in the case of UBSAN ud1s? Do you have any > > > suggestions? > > > > AFAIK on arm64 it's basically a kernel OOPS. > > > > The main thing I just wanted to point out though is that your newly added branch > > > > > if (handle_ubsan_failure(regs, insn) == BUG_TRAP_TYPE_WARN) { > > > > will never be taken, because I don't see where handle_ubsan_failure() > > returns BUG_TRAP_TYPE_WARN. > > > > Initially I wrote this with some symmetry to the KCFI checks nearby, but I > was unsure if this would be considered handled or not. Yeah, that seemed like the right "style" to me too. Perhaps, since it can never warn, we could just rewrite it so it's a void function avoid the checking, etc.
On 29/05/2024 3:20 am, Gatlin Newhouse wrote: > diff --git a/arch/x86/include/asm/bug.h b/arch/x86/include/asm/bug.h > index a3ec87d198ac..e3fbed9073f8 100644 > --- a/arch/x86/include/asm/bug.h > +++ b/arch/x86/include/asm/bug.h > @@ -13,6 +13,14 @@ > #define INSN_UD2 0x0b0f > #define LEN_UD2 2 > > +/* > + * In clang we have UD1s reporting UBSAN failures on X86, 64 and 32bit. > + */ > +#define INSN_UD1 0xb90f > +#define LEN_UD1 2 > +#define INSN_REX 0x67 > +#define LEN_REX 1 That's an address size override prefix, not a REX prefix. What information is actually encoded in this UD1 instruction? I can't find anything any documentation which actually discusses how the ModRM byte is encoded. ~Andrew
On Thu, May 30, 2024 at 01:24:56AM UTC, Andrew Cooper wrote: > On 29/05/2024 3:20 am, Gatlin Newhouse wrote: > > diff --git a/arch/x86/include/asm/bug.h b/arch/x86/include/asm/bug.h > > index a3ec87d198ac..e3fbed9073f8 100644 > > --- a/arch/x86/include/asm/bug.h > > +++ b/arch/x86/include/asm/bug.h > > @@ -13,6 +13,14 @@ > > #define INSN_UD2 0x0b0f > > #define LEN_UD2 2 > > > > +/* > > + * In clang we have UD1s reporting UBSAN failures on X86, 64 and 32bit. > > + */ > > +#define INSN_UD1 0xb90f > > +#define LEN_UD1 2 > > +#define INSN_REX 0x67 > > +#define LEN_REX 1 > > That's an address size override prefix, not a REX prefix. Good to know, thanks. > What information is actually encoded in this UD1 instruction? I can't > find anything any documentation which actually discusses how the ModRM > byte is encoded. lib/ubsan.h has a comment before the ubsan_checks enum which links to line 113 in LLVM's clang/lib/CodeGen/CodeGenFunction.h which defines the values for the ModRM byte. I think the Undefined Behavior Sanitizer pass does the actual encoding of UB type to values but I'm not an expert in LLVM. > ~Andrew
diff --git a/MAINTAINERS b/MAINTAINERS index 28e20975c26f..b8512887ffb1 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -22635,6 +22635,8 @@ L: kasan-dev@googlegroups.com L: linux-hardening@vger.kernel.org S: Supported T: git git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git for-next/hardening +F: arch/x86/include/asm/ubsan.h +F: arch/x86/kernel/ubsan.c F: Documentation/dev-tools/ubsan.rst F: include/linux/ubsan.h F: lib/Kconfig.ubsan diff --git a/arch/x86/include/asm/bug.h b/arch/x86/include/asm/bug.h index a3ec87d198ac..e3fbed9073f8 100644 --- a/arch/x86/include/asm/bug.h +++ b/arch/x86/include/asm/bug.h @@ -13,6 +13,14 @@ #define INSN_UD2 0x0b0f #define LEN_UD2 2 +/* + * In clang we have UD1s reporting UBSAN failures on X86, 64 and 32bit. + */ +#define INSN_UD1 0xb90f +#define LEN_UD1 2 +#define INSN_REX 0x67 +#define LEN_REX 1 + #ifdef CONFIG_GENERIC_BUG #ifdef CONFIG_X86_32 diff --git a/arch/x86/include/asm/ubsan.h b/arch/x86/include/asm/ubsan.h new file mode 100644 index 000000000000..5235822eb4ae --- /dev/null +++ b/arch/x86/include/asm/ubsan.h @@ -0,0 +1,21 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_X86_UBSAN_H +#define _ASM_X86_UBSAN_H + +/* + * Clang Undefined Behavior Sanitizer trap mode support. + */ +#include <linux/bug.h> +#include <linux/ubsan.h> +#include <asm/ptrace.h> + +#ifdef CONFIG_UBSAN_TRAP +enum bug_trap_type handle_ubsan_failure(struct pt_regs *regs, int insn); +#else +static inline enum bug_trap_type handle_ubsan_failure(struct pt_regs *regs, int insn) +{ + return BUG_TRAP_TYPE_NONE; +} +#endif /* CONFIG_UBSAN_TRAP */ + +#endif /* _ASM_X86_UBSAN_H */ diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile index 74077694da7d..fe1d9db27500 100644 --- a/arch/x86/kernel/Makefile +++ b/arch/x86/kernel/Makefile @@ -145,6 +145,7 @@ obj-$(CONFIG_UNWINDER_GUESS) += unwind_guess.o obj-$(CONFIG_AMD_MEM_ENCRYPT) += sev.o obj-$(CONFIG_CFI_CLANG) += cfi.o +obj-$(CONFIG_UBSAN_TRAP) += ubsan.o obj-$(CONFIG_CALL_THUNKS) += callthunks.o diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 4fa0b17e5043..7876449e97a0 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -67,6 +67,7 @@ #include <asm/vdso.h> #include <asm/tdx.h> #include <asm/cfi.h> +#include <asm/ubsan.h> #ifdef CONFIG_X86_64 #include <asm/x86_init.h> @@ -79,6 +80,9 @@ DECLARE_BITMAP(system_vectors, NR_VECTORS); +/* + * Check for UD1, UD2, with or without REX instructions. + */ __always_inline int is_valid_bugaddr(unsigned long addr) { if (addr < TASK_SIZE_MAX) @@ -88,7 +92,13 @@ __always_inline int is_valid_bugaddr(unsigned long addr) * We got #UD, if the text isn't readable we'd have gotten * a different exception. */ - return *(unsigned short *)addr == INSN_UD2; + if (*(u16 *)addr == INSN_UD2) + return INSN_UD2; + if (*(u16 *)addr == INSN_UD1) + return INSN_UD1; + if (*(u8 *)addr == INSN_REX && *(u16 *)(addr + 1) == INSN_UD1) + return INSN_REX; + return 0; } static nokprobe_inline int @@ -216,6 +226,7 @@ static inline void handle_invalid_op(struct pt_regs *regs) static noinstr bool handle_bug(struct pt_regs *regs) { bool handled = false; + int insn; /* * Normally @regs are unpoisoned by irqentry_enter(), but handle_bug() @@ -223,7 +234,8 @@ static noinstr bool handle_bug(struct pt_regs *regs) * irqentry_enter(). */ kmsan_unpoison_entry_regs(regs); - if (!is_valid_bugaddr(regs->ip)) + insn = is_valid_bugaddr(regs->ip); + if (insn == 0) return handled; /* @@ -236,10 +248,20 @@ static noinstr bool handle_bug(struct pt_regs *regs) */ if (regs->flags & X86_EFLAGS_IF) raw_local_irq_enable(); - if (report_bug(regs->ip, regs) == BUG_TRAP_TYPE_WARN || - handle_cfi_failure(regs) == BUG_TRAP_TYPE_WARN) { - regs->ip += LEN_UD2; - handled = true; + + if (insn == INSN_UD2) { + if (report_bug(regs->ip, regs) == BUG_TRAP_TYPE_WARN || + handle_cfi_failure(regs) == BUG_TRAP_TYPE_WARN) { + regs->ip += LEN_UD2; + handled = true; + } + } else { + if (handle_ubsan_failure(regs, insn) == BUG_TRAP_TYPE_WARN) { + if (insn == INSN_REX) + regs->ip += LEN_REX; + regs->ip += LEN_UD1; + handled = true; + } } if (regs->flags & X86_EFLAGS_IF) raw_local_irq_disable(); diff --git a/arch/x86/kernel/ubsan.c b/arch/x86/kernel/ubsan.c new file mode 100644 index 000000000000..6cae11f4fe23 --- /dev/null +++ b/arch/x86/kernel/ubsan.c @@ -0,0 +1,32 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Clang Undefined Behavior Sanitizer trap mode support. + */ +#include <linux/bug.h> +#include <linux/string.h> +#include <linux/printk.h> +#include <linux/ubsan.h> +#include <asm/ptrace.h> +#include <asm/ubsan.h> + +/* + * Checks for the information embedded in the UD1 trap instruction + * for the UB Sanitizer in order to pass along debugging output. + */ +enum bug_trap_type handle_ubsan_failure(struct pt_regs *regs, int insn) +{ + u32 type = 0; + + if (insn == INSN_REX) { + type = (*(u16 *)(regs->ip + LEN_REX + LEN_UD1)); + if ((type & 0xFF) == 0x40) + type = (type >> 8) & 0xFF; + } else { + type = (*(u16 *)(regs->ip + LEN_UD1)); + if ((type & 0xFF) == 0x40) + type = (type >> 8) & 0xFF; + } + pr_crit("%s at %pS\n", report_ubsan_failure(regs, type), (void *)regs->ip); + + return BUG_TRAP_TYPE_NONE; +}
Bring x86 to parity with arm64, similar to commit 25b84002afb9 ("arm64: Support Clang UBSAN trap codes for better reporting"). Enable the output of UBSAN type information on x86 architectures compiled with clang when CONFIG_UBSAN_TRAP=y. Currently ARM architectures output which specific sanitizer caused the trap, via the encoded data in the trap instruction. Clang on x86 currently encodes the same data in ud1 instructions but the x86 handle_bug() and is_valid_bugaddr() functions currently only look at ud2s. Signed-off-by: Gatlin Newhouse <gatlin.newhouse@gmail.com> --- MAINTAINERS | 2 ++ arch/x86/include/asm/bug.h | 8 ++++++++ arch/x86/include/asm/ubsan.h | 21 +++++++++++++++++++++ arch/x86/kernel/Makefile | 1 + arch/x86/kernel/traps.c | 34 ++++++++++++++++++++++++++++------ arch/x86/kernel/ubsan.c | 32 ++++++++++++++++++++++++++++++++ 6 files changed, 92 insertions(+), 6 deletions(-) create mode 100644 arch/x86/include/asm/ubsan.h create mode 100644 arch/x86/kernel/ubsan.c