| Message ID | 20201119190921.3589081-1-pcc@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v20] arm64: expose FAR_EL1 tag bits in siginfo | expand |
Peter Collingbourne <pcc@google.com> writes: > The kernel currently clears the tag bits (i.e. bits 56-63) in the fault > address exposed via siginfo.si_addr and sigcontext.fault_address. However, > the tag bits may be needed by tools in order to accurately diagnose > memory errors, such as HWASan [1] or future tools based on the Memory > Tagging Extension (MTE). > > We should not stop clearing these bits in the existing fault address > fields, because there may be existing userspace applications that are > expecting the tag bits to be cleared. Instead, introduce a flag in > sigaction.sa_flags, SA_EXPOSE_TAGBITS, and only expose the tag bits > there if the signal handler has this flag set. > > [1] http://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html For the generic bits: Acked-by: "Eric W. Biederman" <ebiederm@xmission.com> Some of the arm bits look wrong. There are a couple of cases where it looks like you are deliberately passing an untagged address into functions that normally take tagged addresses. It might be a good idea to have a type distinction between the two. Perhaps "(void __user *)" vs "(unsigned long)" so that accidentally using the wrong one generates a type error. I don't think I am really qualified to review all of the arm details, and I certainly don't want to be in the middle of any arm bugs this code might introduce. If you will split out the generic bits of this patch I will take it. The this whole thing can be merged into the arm tree and you can ensure the arm bits are correct. Eric > diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c > index 1ee94002801f..c5375cb7763d 100644 > --- a/arch/arm64/mm/fault.c > +++ b/arch/arm64/mm/fault.c > @@ -596,33 +596,35 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, > return 0; > } > > -static int __kprobes do_translation_fault(unsigned long addr, > +static int __kprobes do_translation_fault(unsigned long far, > unsigned int esr, > struct pt_regs *regs) > { > + unsigned long addr = untagged_addr(far); > + > if (is_ttbr0_addr(addr)) > - return do_page_fault(addr, esr, regs); > + return do_page_fault(far, esr, regs); > > - do_bad_area(addr, esr, regs); > + do_bad_area(far, esr, regs); > return 0; > } > > -static int do_alignment_fault(unsigned long addr, unsigned int esr, > +static int do_alignment_fault(unsigned long far, unsigned int esr, > struct pt_regs *regs) > { > - do_bad_area(addr, esr, regs); > + do_bad_area(far, esr, regs); > return 0; > } > > -static int do_bad(unsigned long addr, unsigned int esr, struct pt_regs *regs) > +static int do_bad(unsigned long far, unsigned int esr, struct pt_regs *regs) > { > return 1; /* "fault" */ > } > > -static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs) > +static int do_sea(unsigned long far, unsigned int esr, struct pt_regs *regs) > { > const struct fault_info *inf; > - void __user *siaddr; > + unsigned long siaddr; > > inf = esr_to_fault_info(esr); > > @@ -635,18 +637,23 @@ static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs) > } > > if (esr & ESR_ELx_FnV) > - siaddr = NULL; > + siaddr = 0; > else > - siaddr = (void __user *)addr; > + siaddr = untagged_addr(far); > arm64_notify_die(inf->name, regs, inf->sig, inf->code, siaddr, esr); > What is going on in this function? Are you deliberately removing the tag bits? > return 0; > } > > -static int do_tag_check_fault(unsigned long addr, unsigned int esr, > +static int do_tag_check_fault(unsigned long far, unsigned int esr, > struct pt_regs *regs) > { > - do_bad_area(addr, esr, regs); > + /* > + * The architecture specifies that bits 63:60 of FAR_EL1 are UNKNOWN for tag > + * check faults. Mask them out now so that userspace doesn't see them. > + */ > + far &= (1UL << 60) - 1; > + do_bad_area(far, esr, regs); > return 0; > } > > @@ -717,11 +724,12 @@ static const struct fault_info fault_info[] = { > { do_bad, SIGKILL, SI_KERNEL, "unknown 63" }, > }; > > -void do_mem_abort(unsigned long addr, unsigned int esr, struct pt_regs *regs) > +void do_mem_abort(unsigned long far, unsigned int esr, struct pt_regs *regs) > { > const struct fault_info *inf = esr_to_fault_info(esr); > + unsigned long addr = untagged_addr(far); > > - if (!inf->fn(addr, esr, regs)) > + if (!inf->fn(far, esr, regs)) > return; > > if (!user_mode(regs)) { > @@ -730,8 +738,7 @@ void do_mem_abort(unsigned long addr, unsigned int esr, struct pt_regs *regs) > show_pte(addr); > } > > - arm64_notify_die(inf->name, regs, > - inf->sig, inf->code, (void __user *)addr, esr); > + arm64_notify_die(inf->name, regs, inf->sig, inf->code, addr, esr); What is going on in this function? Are you deliberately removing the tag bits? > } > NOKPROBE_SYMBOL(do_mem_abort); >
On Fri, Nov 20, 2020 at 9:44 AM Eric W. Biederman <ebiederm@xmission.com> wrote: > > Peter Collingbourne <pcc@google.com> writes: > > > The kernel currently clears the tag bits (i.e. bits 56-63) in the fault > > address exposed via siginfo.si_addr and sigcontext.fault_address. However, > > the tag bits may be needed by tools in order to accurately diagnose > > memory errors, such as HWASan [1] or future tools based on the Memory > > Tagging Extension (MTE). > > > > We should not stop clearing these bits in the existing fault address > > fields, because there may be existing userspace applications that are > > expecting the tag bits to be cleared. Instead, introduce a flag in > > sigaction.sa_flags, SA_EXPOSE_TAGBITS, and only expose the tag bits > > there if the signal handler has this flag set. > > > > [1] http://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html > > For the generic bits: > Acked-by: "Eric W. Biederman" <ebiederm@xmission.com> Thanks for the review. > Some of the arm bits look wrong. There are a couple of cases where > it looks like you are deliberately passing an untagged address into > functions that normally take tagged addresses. > > It might be a good idea to have a type distinction between the two. > Perhaps "(void __user *)" vs "(unsigned long)" so that accidentally > using the wrong one generates a type error. > > I don't think I am really qualified to review all of the arm details, > and I certainly don't want to be in the middle of any arm bugs this > code might introduce. If you will split out the generic bits of this > patch I will take it. The this whole thing can be merged into the arm Okay, I'll do that. > tree and you can ensure the arm bits are correct. So you want Catalin to merge your signal-for-v5.11 branch with the generic patches into the arm64 tree and then add the arm64-specific patch on top? Works for me. > Eric > > > > diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c > > index 1ee94002801f..c5375cb7763d 100644 > > --- a/arch/arm64/mm/fault.c > > +++ b/arch/arm64/mm/fault.c > > @@ -596,33 +596,35 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, > > return 0; > > } > > > > -static int __kprobes do_translation_fault(unsigned long addr, > > +static int __kprobes do_translation_fault(unsigned long far, > > unsigned int esr, > > struct pt_regs *regs) > > { > > + unsigned long addr = untagged_addr(far); > > + > > if (is_ttbr0_addr(addr)) > > - return do_page_fault(addr, esr, regs); > > + return do_page_fault(far, esr, regs); > > > > - do_bad_area(addr, esr, regs); > > + do_bad_area(far, esr, regs); > > return 0; > > } > > > > -static int do_alignment_fault(unsigned long addr, unsigned int esr, > > +static int do_alignment_fault(unsigned long far, unsigned int esr, > > struct pt_regs *regs) > > { > > - do_bad_area(addr, esr, regs); > > + do_bad_area(far, esr, regs); > > return 0; > > } > > > > -static int do_bad(unsigned long addr, unsigned int esr, struct pt_regs *regs) > > +static int do_bad(unsigned long far, unsigned int esr, struct pt_regs *regs) > > { > > return 1; /* "fault" */ > > } > > > > -static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs) > > +static int do_sea(unsigned long far, unsigned int esr, struct pt_regs *regs) > > { > > const struct fault_info *inf; > > - void __user *siaddr; > > + unsigned long siaddr; > > > > inf = esr_to_fault_info(esr); > > > > @@ -635,18 +637,23 @@ static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs) > > } > > > > if (esr & ESR_ELx_FnV) > > - siaddr = NULL; > > + siaddr = 0; > > else > > - siaddr = (void __user *)addr; > > + siaddr = untagged_addr(far); > > arm64_notify_die(inf->name, regs, inf->sig, inf->code, siaddr, esr); > > > What is going on in this function? > > Are you deliberately removing the tag bits? Yes, this function handles synchronous external aborts, and the architecture defines the tag bits as UNKNOWN for these types of aborts. This is similar to the tag check fault case where bits 63:60 are UNKNOWN. > > return 0; > > } > > > > -static int do_tag_check_fault(unsigned long addr, unsigned int esr, > > +static int do_tag_check_fault(unsigned long far, unsigned int esr, > > struct pt_regs *regs) > > { > > - do_bad_area(addr, esr, regs); > > + /* > > + * The architecture specifies that bits 63:60 of FAR_EL1 are UNKNOWN for tag > > + * check faults. Mask them out now so that userspace doesn't see them. > > + */ > > + far &= (1UL << 60) - 1; > > + do_bad_area(far, esr, regs); > > return 0; > > } > > > > @@ -717,11 +724,12 @@ static const struct fault_info fault_info[] = { > > { do_bad, SIGKILL, SI_KERNEL, "unknown 63" }, > > }; > > > > -void do_mem_abort(unsigned long addr, unsigned int esr, struct pt_regs *regs) > > +void do_mem_abort(unsigned long far, unsigned int esr, struct pt_regs *regs) > > { > > const struct fault_info *inf = esr_to_fault_info(esr); > > + unsigned long addr = untagged_addr(far); > > > > - if (!inf->fn(addr, esr, regs)) > > + if (!inf->fn(far, esr, regs)) > > return; > > > > if (!user_mode(regs)) { > > @@ -730,8 +738,7 @@ void do_mem_abort(unsigned long addr, unsigned int esr, struct pt_regs *regs) > > show_pte(addr); > > } > > > > - arm64_notify_die(inf->name, regs, > > - inf->sig, inf->code, (void __user *)addr, esr); > > + arm64_notify_die(inf->name, regs, inf->sig, inf->code, addr, esr); > > What is going on in this function? > > Are you deliberately removing the tag bits? This part of the function handles the case where the type of the abort is unrecognized. In this case we conservatively remove the tag bits since they may have been defined as UNKNOWN. Peter
Peter Collingbourne <pcc@google.com> writes: > On Fri, Nov 20, 2020 at 9:44 AM Eric W. Biederman <ebiederm@xmission.com> wrote: >> >> Peter Collingbourne <pcc@google.com> writes: >> >> > The kernel currently clears the tag bits (i.e. bits 56-63) in the fault >> > address exposed via siginfo.si_addr and sigcontext.fault_address. However, >> > the tag bits may be needed by tools in order to accurately diagnose >> > memory errors, such as HWASan [1] or future tools based on the Memory >> > Tagging Extension (MTE). >> > >> > We should not stop clearing these bits in the existing fault address >> > fields, because there may be existing userspace applications that are >> > expecting the tag bits to be cleared. Instead, introduce a flag in >> > sigaction.sa_flags, SA_EXPOSE_TAGBITS, and only expose the tag bits >> > there if the signal handler has this flag set. >> > >> > [1] http://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html >> >> For the generic bits: >> Acked-by: "Eric W. Biederman" <ebiederm@xmission.com> > > Thanks for the review. > >> Some of the arm bits look wrong. There are a couple of cases where >> it looks like you are deliberately passing an untagged address into >> functions that normally take tagged addresses. >> >> It might be a good idea to have a type distinction between the two. >> Perhaps "(void __user *)" vs "(unsigned long)" so that accidentally >> using the wrong one generates a type error. >> >> I don't think I am really qualified to review all of the arm details, >> and I certainly don't want to be in the middle of any arm bugs this >> code might introduce. If you will split out the generic bits of this >> patch I will take it. The this whole thing can be merged into the arm > > Okay, I'll do that. Thank you. >> tree and you can ensure the arm bits are correct. > > So you want Catalin to merge your signal-for-v5.11 branch with the > generic patches into the arm64 tree and then add the arm64-specific > patch on top? Works for me. I think that is what we discussed. Unless he has objections I would prefer that. I based the branch on -rc3 in hopes that I would not cause problems for his process. In the cases where I was confused you probably want comments describing why the tag bits are being cleared. It may be obvious when you know the architecture intimately but it certainly was not for me. I certainly don't know the details of arm64 well enough to understand the architecture specific nuances. Eric
On Fri, Nov 20, 2020 at 11:24 AM Eric W. Biederman <ebiederm@xmission.com> wrote: > > Peter Collingbourne <pcc@google.com> writes: > > > On Fri, Nov 20, 2020 at 9:44 AM Eric W. Biederman <ebiederm@xmission.com> wrote: > >> > >> Peter Collingbourne <pcc@google.com> writes: > >> > >> > The kernel currently clears the tag bits (i.e. bits 56-63) in the fault > >> > address exposed via siginfo.si_addr and sigcontext.fault_address. However, > >> > the tag bits may be needed by tools in order to accurately diagnose > >> > memory errors, such as HWASan [1] or future tools based on the Memory > >> > Tagging Extension (MTE). > >> > > >> > We should not stop clearing these bits in the existing fault address > >> > fields, because there may be existing userspace applications that are > >> > expecting the tag bits to be cleared. Instead, introduce a flag in > >> > sigaction.sa_flags, SA_EXPOSE_TAGBITS, and only expose the tag bits > >> > there if the signal handler has this flag set. > >> > > >> > [1] http://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html > >> > >> For the generic bits: > >> Acked-by: "Eric W. Biederman" <ebiederm@xmission.com> > > > > Thanks for the review. > > > >> Some of the arm bits look wrong. There are a couple of cases where > >> it looks like you are deliberately passing an untagged address into > >> functions that normally take tagged addresses. > >> > >> It might be a good idea to have a type distinction between the two. > >> Perhaps "(void __user *)" vs "(unsigned long)" so that accidentally > >> using the wrong one generates a type error. > >> > >> I don't think I am really qualified to review all of the arm details, > >> and I certainly don't want to be in the middle of any arm bugs this > >> code might introduce. If you will split out the generic bits of this > >> patch I will take it. The this whole thing can be merged into the arm > > > > Okay, I'll do that. > > Thank you. Sent out v21 with the generic parts split out. > >> tree and you can ensure the arm bits are correct. > > > > So you want Catalin to merge your signal-for-v5.11 branch with the > > generic patches into the arm64 tree and then add the arm64-specific > > patch on top? Works for me. > > I think that is what we discussed. Unless he has objections I would > prefer that. I based the branch on -rc3 in hopes that I would > not cause problems for his process. > > In the cases where I was confused you probably want comments describing > why the tag bits are being cleared. It may be obvious when you know the > architecture intimately but it certainly was not for me. I certainly > don't know the details of arm64 well enough to understand the > architecture specific nuances. I think that makes sense. I've added comments to those two cases. Peter
diff --git a/Documentation/arm64/tagged-pointers.rst b/Documentation/arm64/tagged-pointers.rst index eab4323609b9..19d284b70384 100644 --- a/Documentation/arm64/tagged-pointers.rst +++ b/Documentation/arm64/tagged-pointers.rst @@ -53,12 +53,25 @@ visibility. Preserving tags --------------- -Non-zero tags are not preserved when delivering signals. This means that -signal handlers in applications making use of tags cannot rely on the -tag information for user virtual addresses being maintained for fields -inside siginfo_t. One exception to this rule is for signals raised in -response to watchpoint debug exceptions, where the tag information will -be preserved. +When delivering signals, non-zero tags are not preserved in +siginfo.si_addr unless the flag SA_EXPOSE_TAGBITS was set in +sigaction.sa_flags when the signal handler was installed. This means +that signal handlers in applications making use of tags cannot rely +on the tag information for user virtual addresses being maintained +in these fields unless the flag was set. + +Due to architecture limitations, bits 63:60 of the fault address +are not preserved in response to synchronous tag check faults +(SEGV_MTESERR) even if SA_EXPOSE_TAGBITS was set. Applications should +treat the values of these bits as undefined in order to accommodate +future architecture revisions which may preserve the bits. + +For signals raised in response to watchpoint debug exceptions, the +tag information will be preserved regardless of the SA_EXPOSE_TAGBITS +flag setting. + +Non-zero tags are never preserved in sigcontext.fault_address +regardless of the SA_EXPOSE_TAGBITS flag setting. The architecture prevents the use of a tagged PC, so the upper byte will be set to a sign-extension of bit 55 on exception return. diff --git a/arch/arm64/include/asm/exception.h b/arch/arm64/include/asm/exception.h index 99b9383cd036..2a8aa1884d8a 100644 --- a/arch/arm64/include/asm/exception.h +++ b/arch/arm64/include/asm/exception.h @@ -32,7 +32,7 @@ static inline u32 disr_to_esr(u64 disr) } asmlinkage void enter_from_user_mode(void); -void do_mem_abort(unsigned long addr, unsigned int esr, struct pt_regs *regs); +void do_mem_abort(unsigned long far, unsigned int esr, struct pt_regs *regs); void do_undefinstr(struct pt_regs *regs); void do_bti(struct pt_regs *regs); asmlinkage void bad_mode(struct pt_regs *regs, int reason, unsigned int esr); diff --git a/arch/arm64/include/asm/signal.h b/arch/arm64/include/asm/signal.h new file mode 100644 index 000000000000..ef449f5f4ba8 --- /dev/null +++ b/arch/arm64/include/asm/signal.h @@ -0,0 +1,25 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __ARM64_ASM_SIGNAL_H +#define __ARM64_ASM_SIGNAL_H + +#include <asm/memory.h> +#include <uapi/asm/signal.h> +#include <uapi/asm/siginfo.h> + +static inline void __user *arch_untagged_si_addr(void __user *addr, + unsigned long sig, + unsigned long si_code) +{ + /* + * For historical reasons, all bits of the fault address are exposed as + * address bits for watchpoint exceptions. New architectures should + * handle the tag bits consistently. + */ + if (sig == SIGTRAP && si_code == TRAP_BRKPT) + return addr; + + return untagged_addr(addr); +} +#define arch_untagged_si_addr arch_untagged_si_addr + +#endif diff --git a/arch/arm64/include/asm/system_misc.h b/arch/arm64/include/asm/system_misc.h index 1ab63cfbbaf1..673be2d1263c 100644 --- a/arch/arm64/include/asm/system_misc.h +++ b/arch/arm64/include/asm/system_misc.h @@ -22,7 +22,7 @@ void die(const char *msg, struct pt_regs *regs, int err); struct siginfo; void arm64_notify_die(const char *str, struct pt_regs *regs, - int signo, int sicode, void __user *addr, + int signo, int sicode, unsigned long far, int err); void hook_debug_fault_code(int nr, int (*fn)(unsigned long, unsigned int, diff --git a/arch/arm64/include/asm/traps.h b/arch/arm64/include/asm/traps.h index d96dc2c7c09d..54f32a0675df 100644 --- a/arch/arm64/include/asm/traps.h +++ b/arch/arm64/include/asm/traps.h @@ -26,9 +26,9 @@ void register_undef_hook(struct undef_hook *hook); void unregister_undef_hook(struct undef_hook *hook); void force_signal_inject(int signal, int code, unsigned long address, unsigned int err); void arm64_notify_segfault(unsigned long addr); -void arm64_force_sig_fault(int signo, int code, void __user *addr, const char *str); -void arm64_force_sig_mceerr(int code, void __user *addr, short lsb, const char *str); -void arm64_force_sig_ptrace_errno_trap(int errno, void __user *addr, const char *str); +void arm64_force_sig_fault(int signo, int code, unsigned long far, const char *str); +void arm64_force_sig_mceerr(int code, unsigned long far, short lsb, const char *str); +void arm64_force_sig_ptrace_errno_trap(int errno, unsigned long far, const char *str); /* * Move regs->pc to next instruction and do necessary setup before it diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c index fa76151de6ff..4f3661eeb7ec 100644 --- a/arch/arm64/kernel/debug-monitors.c +++ b/arch/arm64/kernel/debug-monitors.c @@ -234,9 +234,8 @@ static void send_user_sigtrap(int si_code) if (interrupts_enabled(regs)) local_irq_enable(); - arm64_force_sig_fault(SIGTRAP, si_code, - (void __user *)instruction_pointer(regs), - "User debug trap"); + arm64_force_sig_fault(SIGTRAP, si_code, instruction_pointer(regs), + "User debug trap"); } static int single_step_handler(unsigned long unused, unsigned int esr, diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c index 43d4c329775f..dbbddfbf4a72 100644 --- a/arch/arm64/kernel/entry-common.c +++ b/arch/arm64/kernel/entry-common.c @@ -22,7 +22,6 @@ static void notrace el1_abort(struct pt_regs *regs, unsigned long esr) unsigned long far = read_sysreg(far_el1); local_daif_inherit(regs); - far = untagged_addr(far); do_mem_abort(far, esr, regs); } NOKPROBE_SYMBOL(el1_abort); @@ -114,7 +113,6 @@ static void notrace el0_da(struct pt_regs *regs, unsigned long esr) user_exit_irqoff(); local_daif_restore(DAIF_PROCCTX); - far = untagged_addr(far); do_mem_abort(far, esr, regs); } NOKPROBE_SYMBOL(el0_da); diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c index f49b349e16a3..8ac487c84e37 100644 --- a/arch/arm64/kernel/ptrace.c +++ b/arch/arm64/kernel/ptrace.c @@ -192,14 +192,11 @@ static void ptrace_hbptriggered(struct perf_event *bp, break; } } - arm64_force_sig_ptrace_errno_trap(si_errno, - (void __user *)bkpt->trigger, + arm64_force_sig_ptrace_errno_trap(si_errno, bkpt->trigger, desc); } #endif - arm64_force_sig_fault(SIGTRAP, TRAP_HWBKPT, - (void __user *)(bkpt->trigger), - desc); + arm64_force_sig_fault(SIGTRAP, TRAP_HWBKPT, bkpt->trigger, desc); } /* diff --git a/arch/arm64/kernel/sys_compat.c b/arch/arm64/kernel/sys_compat.c index 3c18c2454089..265fe3eb1069 100644 --- a/arch/arm64/kernel/sys_compat.c +++ b/arch/arm64/kernel/sys_compat.c @@ -68,7 +68,7 @@ do_compat_cache_op(unsigned long start, unsigned long end, int flags) */ long compat_arm_syscall(struct pt_regs *regs, int scno) { - void __user *addr; + unsigned long addr; switch (scno) { /* @@ -111,8 +111,7 @@ long compat_arm_syscall(struct pt_regs *regs, int scno) break; } - addr = (void __user *)instruction_pointer(regs) - - (compat_thumb_mode(regs) ? 2 : 4); + addr = instruction_pointer(regs) - (compat_thumb_mode(regs) ? 2 : 4); arm64_notify_die("Oops - bad compat syscall(2)", regs, SIGILL, ILL_ILLTRP, addr, scno); diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c index 8af4e0e85736..f4ddbe9ed3f1 100644 --- a/arch/arm64/kernel/traps.c +++ b/arch/arm64/kernel/traps.c @@ -170,32 +170,32 @@ static void arm64_show_signal(int signo, const char *str) __show_regs(regs); } -void arm64_force_sig_fault(int signo, int code, void __user *addr, +void arm64_force_sig_fault(int signo, int code, unsigned long far, const char *str) { arm64_show_signal(signo, str); if (signo == SIGKILL) force_sig(SIGKILL); else - force_sig_fault(signo, code, addr); + force_sig_fault(signo, code, (void __user *)far); } -void arm64_force_sig_mceerr(int code, void __user *addr, short lsb, +void arm64_force_sig_mceerr(int code, unsigned long far, short lsb, const char *str) { arm64_show_signal(SIGBUS, str); - force_sig_mceerr(code, addr, lsb); + force_sig_mceerr(code, (void __user *)far, lsb); } -void arm64_force_sig_ptrace_errno_trap(int errno, void __user *addr, +void arm64_force_sig_ptrace_errno_trap(int errno, unsigned long far, const char *str) { arm64_show_signal(SIGTRAP, str); - force_sig_ptrace_errno_trap(errno, addr); + force_sig_ptrace_errno_trap(errno, (void __user *)far); } void arm64_notify_die(const char *str, struct pt_regs *regs, - int signo, int sicode, void __user *addr, + int signo, int sicode, unsigned long far, int err) { if (user_mode(regs)) { @@ -203,7 +203,7 @@ void arm64_notify_die(const char *str, struct pt_regs *regs, current->thread.fault_address = 0; current->thread.fault_code = err; - arm64_force_sig_fault(signo, sicode, addr, str); + arm64_force_sig_fault(signo, sicode, far, str); } else { die(str, regs, err); } @@ -374,7 +374,7 @@ void force_signal_inject(int signal, int code, unsigned long address, unsigned i signal = SIGKILL; } - arm64_notify_die(desc, regs, signal, code, (void __user *)address, err); + arm64_notify_die(desc, regs, signal, code, address, err); } /* @@ -385,7 +385,7 @@ void arm64_notify_segfault(unsigned long addr) int code; mmap_read_lock(current->mm); - if (find_vma(current->mm, addr) == NULL) + if (find_vma(current->mm, untagged_addr(addr)) == NULL) code = SEGV_MAPERR; else code = SEGV_ACCERR; @@ -448,12 +448,13 @@ NOKPROBE_SYMBOL(do_ptrauth_fault); static void user_cache_maint_handler(unsigned int esr, struct pt_regs *regs) { - unsigned long address; + unsigned long tagged_address, address; int rt = ESR_ELx_SYS64_ISS_RT(esr); int crm = (esr & ESR_ELx_SYS64_ISS_CRM_MASK) >> ESR_ELx_SYS64_ISS_CRM_SHIFT; int ret = 0; - address = untagged_addr(pt_regs_read_reg(regs, rt)); + tagged_address = pt_regs_read_reg(regs, rt); + address = untagged_addr(tagged_address); switch (crm) { case ESR_ELx_SYS64_ISS_CRM_DC_CVAU: /* DC CVAU, gets promoted */ @@ -480,7 +481,7 @@ static void user_cache_maint_handler(unsigned int esr, struct pt_regs *regs) } if (ret) - arm64_notify_segfault(address); + arm64_notify_segfault(tagged_address); else arm64_skip_faulting_instruction(regs, AARCH64_INSN_SIZE); } @@ -772,7 +773,7 @@ asmlinkage void bad_mode(struct pt_regs *regs, int reason, unsigned int esr) */ void bad_el0_sync(struct pt_regs *regs, int reason, unsigned int esr) { - void __user *pc = (void __user *)instruction_pointer(regs); + unsigned long pc = instruction_pointer(regs); current->thread.fault_address = 0; current->thread.fault_code = esr; diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index 1ee94002801f..c5375cb7763d 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -40,7 +40,7 @@ #include <asm/traps.h> struct fault_info { - int (*fn)(unsigned long addr, unsigned int esr, + int (*fn)(unsigned long far, unsigned int esr, struct pt_regs *regs); int sig; int code; @@ -385,8 +385,11 @@ static void set_thread_esr(unsigned long address, unsigned int esr) current->thread.fault_code = esr; } -static void do_bad_area(unsigned long addr, unsigned int esr, struct pt_regs *regs) +static void do_bad_area(unsigned long far, unsigned int esr, + struct pt_regs *regs) { + unsigned long addr = untagged_addr(far); + /* * If we are in kernel mode at this point, we have no context to * handle this fault with. @@ -395,8 +398,7 @@ static void do_bad_area(unsigned long addr, unsigned int esr, struct pt_regs *re const struct fault_info *inf = esr_to_fault_info(esr); set_thread_esr(addr, esr); - arm64_force_sig_fault(inf->sig, inf->code, (void __user *)addr, - inf->name); + arm64_force_sig_fault(inf->sig, inf->code, far, inf->name); } else { __do_kernel_fault(addr, esr, regs); } @@ -448,7 +450,7 @@ static bool is_write_abort(unsigned int esr) return (esr & ESR_ELx_WNR) && !(esr & ESR_ELx_CM); } -static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, +static int __kprobes do_page_fault(unsigned long far, unsigned int esr, struct pt_regs *regs) { const struct fault_info *inf; @@ -456,6 +458,7 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, vm_fault_t fault; unsigned long vm_flags = VM_ACCESS_FLAGS; unsigned int mm_flags = FAULT_FLAG_DEFAULT; + unsigned long addr = untagged_addr(far); if (kprobe_page_fault(regs, esr)) return 0; @@ -567,8 +570,7 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, * We had some memory, but were unable to successfully fix up * this page fault. */ - arm64_force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)addr, - inf->name); + arm64_force_sig_fault(SIGBUS, BUS_ADRERR, far, inf->name); } else if (fault & (VM_FAULT_HWPOISON_LARGE | VM_FAULT_HWPOISON)) { unsigned int lsb; @@ -576,8 +578,7 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, if (fault & VM_FAULT_HWPOISON_LARGE) lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault)); - arm64_force_sig_mceerr(BUS_MCEERR_AR, (void __user *)addr, lsb, - inf->name); + arm64_force_sig_mceerr(BUS_MCEERR_AR, far, lsb, inf->name); } else { /* * Something tried to access memory that isn't in our memory @@ -585,8 +586,7 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, */ arm64_force_sig_fault(SIGSEGV, fault == VM_FAULT_BADACCESS ? SEGV_ACCERR : SEGV_MAPERR, - (void __user *)addr, - inf->name); + far, inf->name); } return 0; @@ -596,33 +596,35 @@ static int __kprobes do_page_fault(unsigned long addr, unsigned int esr, return 0; } -static int __kprobes do_translation_fault(unsigned long addr, +static int __kprobes do_translation_fault(unsigned long far, unsigned int esr, struct pt_regs *regs) { + unsigned long addr = untagged_addr(far); + if (is_ttbr0_addr(addr)) - return do_page_fault(addr, esr, regs); + return do_page_fault(far, esr, regs); - do_bad_area(addr, esr, regs); + do_bad_area(far, esr, regs); return 0; } -static int do_alignment_fault(unsigned long addr, unsigned int esr, +static int do_alignment_fault(unsigned long far, unsigned int esr, struct pt_regs *regs) { - do_bad_area(addr, esr, regs); + do_bad_area(far, esr, regs); return 0; } -static int do_bad(unsigned long addr, unsigned int esr, struct pt_regs *regs) +static int do_bad(unsigned long far, unsigned int esr, struct pt_regs *regs) { return 1; /* "fault" */ } -static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs) +static int do_sea(unsigned long far, unsigned int esr, struct pt_regs *regs) { const struct fault_info *inf; - void __user *siaddr; + unsigned long siaddr; inf = esr_to_fault_info(esr); @@ -635,18 +637,23 @@ static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs) } if (esr & ESR_ELx_FnV) - siaddr = NULL; + siaddr = 0; else - siaddr = (void __user *)addr; + siaddr = untagged_addr(far); arm64_notify_die(inf->name, regs, inf->sig, inf->code, siaddr, esr); return 0; } -static int do_tag_check_fault(unsigned long addr, unsigned int esr, +static int do_tag_check_fault(unsigned long far, unsigned int esr, struct pt_regs *regs) { - do_bad_area(addr, esr, regs); + /* + * The architecture specifies that bits 63:60 of FAR_EL1 are UNKNOWN for tag + * check faults. Mask them out now so that userspace doesn't see them. + */ + far &= (1UL << 60) - 1; + do_bad_area(far, esr, regs); return 0; } @@ -717,11 +724,12 @@ static const struct fault_info fault_info[] = { { do_bad, SIGKILL, SI_KERNEL, "unknown 63" }, }; -void do_mem_abort(unsigned long addr, unsigned int esr, struct pt_regs *regs) +void do_mem_abort(unsigned long far, unsigned int esr, struct pt_regs *regs) { const struct fault_info *inf = esr_to_fault_info(esr); + unsigned long addr = untagged_addr(far); - if (!inf->fn(addr, esr, regs)) + if (!inf->fn(far, esr, regs)) return; if (!user_mode(regs)) { @@ -730,8 +738,7 @@ void do_mem_abort(unsigned long addr, unsigned int esr, struct pt_regs *regs) show_pte(addr); } - arm64_notify_die(inf->name, regs, - inf->sig, inf->code, (void __user *)addr, esr); + arm64_notify_die(inf->name, regs, inf->sig, inf->code, addr, esr); } NOKPROBE_SYMBOL(do_mem_abort); @@ -744,8 +751,8 @@ NOKPROBE_SYMBOL(do_el0_irq_bp_hardening); void do_sp_pc_abort(unsigned long addr, unsigned int esr, struct pt_regs *regs) { - arm64_notify_die("SP/PC alignment exception", regs, - SIGBUS, BUS_ADRALN, (void __user *)addr, esr); + arm64_notify_die("SP/PC alignment exception", regs, SIGBUS, BUS_ADRALN, + addr, esr); } NOKPROBE_SYMBOL(do_sp_pc_abort); @@ -871,8 +878,7 @@ void do_debug_exception(unsigned long addr_if_watchpoint, unsigned int esr, arm64_apply_bp_hardening(); if (inf->fn(addr_if_watchpoint, esr, regs)) { - arm64_notify_die(inf->name, regs, - inf->sig, inf->code, (void __user *)pc, esr); + arm64_notify_die(inf->name, regs, inf->sig, inf->code, pc, esr); } debug_exception_exit(regs); diff --git a/include/linux/signal.h b/include/linux/signal.h index b256f9c65661..205526c4003a 100644 --- a/include/linux/signal.h +++ b/include/linux/signal.h @@ -469,4 +469,18 @@ struct seq_file; extern void render_sigset_t(struct seq_file *, const char *, sigset_t *); #endif +#ifndef arch_untagged_si_addr +/* + * Given a fault address and a signal and si_code which correspond to the + * _sigfault union member, returns the address that must appear in si_addr if + * the signal handler does not have SA_EXPOSE_TAGBITS enabled in sa_flags. + */ +static inline void __user *arch_untagged_si_addr(void __user *addr, + unsigned long sig, + unsigned long si_code) +{ + return addr; +} +#endif + #endif /* _LINUX_SIGNAL_H */ diff --git a/include/linux/signal_types.h b/include/linux/signal_types.h index a7887ad84d36..68e06c75c5b2 100644 --- a/include/linux/signal_types.h +++ b/include/linux/signal_types.h @@ -78,6 +78,6 @@ struct ksignal { #define UAPI_SA_FLAGS \ (SA_NOCLDSTOP | SA_NOCLDWAIT | SA_SIGINFO | SA_ONSTACK | SA_RESTART | \ - SA_NODEFER | SA_RESETHAND | __ARCH_UAPI_SA_FLAGS) + SA_NODEFER | SA_RESETHAND | SA_EXPOSE_TAGBITS | __ARCH_UAPI_SA_FLAGS) #endif /* _LINUX_SIGNAL_TYPES_H */ diff --git a/include/uapi/asm-generic/signal-defs.h b/include/uapi/asm-generic/signal-defs.h index c790f67304ba..fe929e7b77ca 100644 --- a/include/uapi/asm-generic/signal-defs.h +++ b/include/uapi/asm-generic/signal-defs.h @@ -20,6 +20,8 @@ * so this bit allows flag bit support to be detected from userspace while * allowing an old kernel to be distinguished from a kernel that supports every * flag bit. + * SA_EXPOSE_TAGBITS exposes an architecture-defined set of tag bits in + * siginfo.si_addr. * * SA_ONESHOT and SA_NOMASK are the historical Linux names for the Single * Unix names RESETHAND and NODEFER respectively. @@ -41,6 +43,7 @@ /* 0x00000100 used on sparc */ /* 0x00000200 used on sparc */ #define SA_UNSUPPORTED 0x00000400 +#define SA_EXPOSE_TAGBITS 0x00000800 /* 0x00010000 used on mips */ /* 0x01000000 used on x86 */ /* 0x02000000 used on x86 */ diff --git a/kernel/signal.c b/kernel/signal.c index 8f34819e80de..26018c59821d 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -2524,6 +2524,26 @@ static int ptrace_signal(int signr, kernel_siginfo_t *info) return signr; } +static void hide_si_addr_tag_bits(struct ksignal *ksig) +{ + switch (siginfo_layout(ksig->sig, ksig->info.si_code)) { + case SIL_FAULT: + case SIL_FAULT_MCEERR: + case SIL_FAULT_BNDERR: + case SIL_FAULT_PKUERR: + ksig->info.si_addr = arch_untagged_si_addr( + ksig->info.si_addr, ksig->sig, ksig->info.si_code); + break; + case SIL_KILL: + case SIL_TIMER: + case SIL_POLL: + case SIL_CHLD: + case SIL_RT: + case SIL_SYS: + break; + } +} + bool get_signal(struct ksignal *ksig) { struct sighand_struct *sighand = current->sighand; @@ -2761,6 +2781,10 @@ bool get_signal(struct ksignal *ksig) spin_unlock_irq(&sighand->siglock); ksig->sig = signr; + + if (!(ksig->ka.sa.sa_flags & SA_EXPOSE_TAGBITS)) + hide_si_addr_tag_bits(ksig); + return ksig->sig > 0; }