On Thu, Nov 12, 2020 at 6:46 PM Peter Collingbourne <pcc@xxxxxxxxxx> wrote: > > 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 > > Signed-off-by: Peter Collingbourne <pcc@xxxxxxxxxx> > Link: https://linux-review.googlesource.com/id/Ia8876bad8c798e0a32df7c2ce1256c4771c81446 > --- > v15: > - switched to the SA_EXPOSE_TAGBITS approach > proposed by Eric > - rebased to 5.10-rc3 > > v14: > - fix an inaccuracy in the commit message > - add some comments to arch_addr_tag_bits_mask > > v13: > - renamed si_xflags to si_faultflags > - rebased to 5.10-rc2 > > v12: > - add new fields to signal_compat.c test cases > - rebased to 5.10-rc1 > - mask out bits 63:60 for tag check faults > > v11: > - add a comment explaining what the arch hook should do > - rename ignored bits to tag bits > > v10: > - rename the flag to SIFAULTFLAG_ADDR_IGNORED_BITS > - use an arch hook to specify which bits are ignored, instead > of passing them explicitly > - while refactoring for the arch hook, noticed that my previous > patches missed a case involving cache maintenance instructions, > so expose the tag bits for that signal as well > > v9: > - make the ignored bits fields generic > - add some new dependent patches that prepare us to store the > field in such a way that userspace can detect their presence > > v8: > - rebase onto 5.8rc2 > > v7: > - switch to a new siginfo field instead of using sigcontext > - merge the patch back into one since the other patches are now > unnecessary > > v6: > - move fault address and fault code into the kernel_siginfo data structure > - split the patch in three since it was getting large and now has > generic and arch-specific parts > > v5: > - add padding to fault_addr_top_byte_context in order to ensure the correct > size and preserve sp alignment > > v4: > - expose only the tag bits in the context instead of the entire FAR_EL1 > - remove mention of the new context from the sigcontext.__reserved[] note > > v3: > - add documentation to tagged-pointers.rst > - update comments in sigcontext.h > > v2: > - revert changes to hw_breakpoint.c > - rename set_thread_esr to set_thread_far_esr > > Documentation/arm64/tagged-pointers.rst | 25 ++++++--- > arch/arm64/include/asm/exception.h | 2 +- > arch/arm64/include/asm/system_misc.h | 2 +- > arch/arm64/include/asm/traps.h | 6 +-- > arch/arm64/kernel/debug-monitors.c | 5 +- > arch/arm64/kernel/entry-common.c | 2 - > arch/arm64/kernel/ptrace.c | 7 +-- > arch/arm64/kernel/sys_compat.c | 5 +- > arch/arm64/kernel/traps.c | 29 ++++++----- > arch/arm64/mm/fault.c | 68 ++++++++++++++----------- > include/linux/signal.h | 14 +++++ > include/linux/signal_types.h | 2 +- > include/uapi/asm-generic/signal-defs.h | 3 ++ > kernel/signal.c | 23 ++++++--- > 14 files changed, 116 insertions(+), 77 deletions(-) I forgot to add the file arch/arm64/include/asm/signal.h to this patch. Will send a v16 with this fixed. Sorry for the noise. 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/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 0126ebda4d31..5276bdd4a9e2 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. > @@ -49,6 +51,7 @@ > #define SA_RESETHAND 0x80000000 > #endif > #define SA_UNSUPPORTED 0x00000400 > +#define SA_EXPOSE_TAGBITS 0x00000800 > > #define SA_NOMASK SA_NODEFER > #define SA_ONESHOT SA_RESETHAND > diff --git a/kernel/signal.c b/kernel/signal.c > index 8f34819e80de..16be62e6d341 100644 > --- a/kernel/signal.c > +++ b/kernel/signal.c > @@ -1650,6 +1650,15 @@ void force_sigsegv(int sig) > force_sig(SIGSEGV); > } > > +static void __user *get_si_addr(void __user *addr, unsigned long sig, > + unsigned long si_code) > +{ > + if (current->sighand->action[sig - 1].sa.sa_flags & SA_EXPOSE_TAGBITS) > + return addr; > + > + return arch_untagged_si_addr(addr, sig, si_code); > +} > + > int force_sig_fault_to_task(int sig, int code, void __user *addr > ___ARCH_SI_TRAPNO(int trapno) > ___ARCH_SI_IA64(int imm, unsigned int flags, unsigned long isr) > @@ -1661,7 +1670,7 @@ int force_sig_fault_to_task(int sig, int code, void __user *addr > info.si_signo = sig; > info.si_errno = 0; > info.si_code = code; > - info.si_addr = addr; > + info.si_addr = get_si_addr(addr, sig, code); > #ifdef __ARCH_SI_TRAPNO > info.si_trapno = trapno; > #endif > @@ -1693,7 +1702,7 @@ int send_sig_fault(int sig, int code, void __user *addr > info.si_signo = sig; > info.si_errno = 0; > info.si_code = code; > - info.si_addr = addr; > + info.si_addr = get_si_addr(addr, sig, code); > #ifdef __ARCH_SI_TRAPNO > info.si_trapno = trapno; > #endif > @@ -1714,7 +1723,7 @@ int force_sig_mceerr(int code, void __user *addr, short lsb) > info.si_signo = SIGBUS; > info.si_errno = 0; > info.si_code = code; > - info.si_addr = addr; > + info.si_addr = get_si_addr(addr, SIGBUS, code); > info.si_addr_lsb = lsb; > return force_sig_info(&info); > } > @@ -1728,7 +1737,7 @@ int send_sig_mceerr(int code, void __user *addr, short lsb, struct task_struct * > info.si_signo = SIGBUS; > info.si_errno = 0; > info.si_code = code; > - info.si_addr = addr; > + info.si_addr = get_si_addr(addr, SIGBUS, code); > info.si_addr_lsb = lsb; > return send_sig_info(info.si_signo, &info, t); > } > @@ -1742,7 +1751,7 @@ int force_sig_bnderr(void __user *addr, void __user *lower, void __user *upper) > info.si_signo = SIGSEGV; > info.si_errno = 0; > info.si_code = SEGV_BNDERR; > - info.si_addr = addr; > + info.si_addr = get_si_addr(addr, SIGSEGV, SEGV_BNDERR); > info.si_lower = lower; > info.si_upper = upper; > return force_sig_info(&info); > @@ -1757,7 +1766,7 @@ int force_sig_pkuerr(void __user *addr, u32 pkey) > info.si_signo = SIGSEGV; > info.si_errno = 0; > info.si_code = SEGV_PKUERR; > - info.si_addr = addr; > + info.si_addr = get_si_addr(addr, SIGSEGV, SEGV_PKUERR); > info.si_pkey = pkey; > return force_sig_info(&info); > } > @@ -1774,7 +1783,7 @@ int force_sig_ptrace_errno_trap(int errno, void __user *addr) > info.si_signo = SIGTRAP; > info.si_errno = errno; > info.si_code = TRAP_HWBKPT; > - info.si_addr = addr; > + info.si_addr = get_si_addr(addr, SIGTRAP, TRAP_HWBKPT); > return force_sig_info(&info); > } > > -- > 2.29.2.299.gdc1121823c-goog >
