From abd4f7505bafdd6c5319fe3cb5caf9af6104e17a Mon Sep 17 00:00:00 2001 From: Masoud Asgharifard Sharbiani Date: Sun, 22 Jul 2007 11:12:28 +0200 Subject: [PATCH] x86: i386-show-unhandled-signals-v3 This patch makes the i386 behave the same way that x86_64 does when a segfault happens. A line gets printed to the kernel log so that tools that need to check for failures can behave more uniformly between debug.show_unhandled_signals sysctl variable to 0 (or by doing echo 0 > /proc/sys/debug/exception-trace) Also, all of the lines being printed are now using printk_ratelimit() to deny the ability of DoS from a local user with a program like the following: main() { while (1) if (!fork()) *(int *)0 = 0; } This new revision also includes the fix that Andrew did which got rid of new sysctl that was added to the system in earlier versions of this. Also, 'show-unhandled-signals' sysctl has been renamed back to the old 'exception-trace' to avoid breakage of people's scripts. AK: Enabling by default for i386 will be likely controversal, but let's see what happens AK: Really folks, before complaining just fix your segfaults AK: I bet this will find a lot of silent issues Signed-off-by: Masoud Sharbiani Signed-off-by: Andi Kleen [ Personally, I've found the complaints useful on x86-64, so I'm all for this. That said, I wonder if we could do it more prettily.. -Linus ] Signed-off-by: Linus Torvalds --- arch/i386/kernel/signal.c | 7 +++++++ arch/i386/kernel/traps.c | 7 +++++++ arch/i386/mm/fault.c | 10 ++++++++++ arch/x86_64/kernel/signal.c | 2 +- arch/x86_64/kernel/traps.c | 6 ++++-- arch/x86_64/mm/fault.c | 15 +++------------ arch/x86_64/mm/init.c | 33 --------------------------------- include/asm-x86_64/proto.h | 2 -- include/linux/signal.h | 3 +++ kernel/signal.c | 10 ++++++++++ kernel/sysctl.c | 10 ++++++++++ 11 files changed, 55 insertions(+), 50 deletions(-) diff --git a/arch/i386/kernel/signal.c b/arch/i386/kernel/signal.c index d574e38f0f7..f5dd85656c1 100644 --- a/arch/i386/kernel/signal.c +++ b/arch/i386/kernel/signal.c @@ -199,6 +199,13 @@ asmlinkage int sys_sigreturn(unsigned long __unused) return eax; badframe: + if (show_unhandled_signals && printk_ratelimit()) + printk("%s%s[%d] bad frame in sigreturn frame:%p eip:%lx" + " esp:%lx oeax:%lx\n", + current->pid > 1 ? KERN_INFO : KERN_EMERG, + current->comm, current->pid, frame, regs->eip, + regs->esp, regs->orig_eax); + force_sig(SIGSEGV, current); return 0; } diff --git a/arch/i386/kernel/traps.c b/arch/i386/kernel/traps.c index 57772a18c39..438949da3b6 100644 --- a/arch/i386/kernel/traps.c +++ b/arch/i386/kernel/traps.c @@ -618,6 +618,13 @@ fastcall void __kprobes do_general_protection(struct pt_regs * regs, current->thread.error_code = error_code; current->thread.trap_no = 13; + if (show_unhandled_signals && unhandled_signal(current, SIGSEGV) && + printk_ratelimit()) + printk(KERN_INFO + "%s[%d] general protection eip:%lx esp:%lx error:%lx\n", + current->comm, current->pid, + regs->eip, regs->esp, error_code); + force_sig(SIGSEGV, current); return; diff --git a/arch/i386/mm/fault.c b/arch/i386/mm/fault.c index e92a1012493..01ffdd4964f 100644 --- a/arch/i386/mm/fault.c +++ b/arch/i386/mm/fault.c @@ -283,6 +283,8 @@ static inline int vmalloc_fault(unsigned long address) return 0; } +int show_unhandled_signals = 1; + /* * This routine handles page faults. It determines the address, * and the problem, and then passes it off to one of the appropriate @@ -469,6 +471,14 @@ bad_area_nosemaphore: if (is_prefetch(regs, address, error_code)) return; + if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) && + printk_ratelimit()) { + printk("%s%s[%d]: segfault at %08lx eip %08lx " + "esp %08lx error %lx\n", + tsk->pid > 1 ? KERN_INFO : KERN_EMERG, + tsk->comm, tsk->pid, address, regs->eip, + regs->esp, error_code); + } tsk->thread.cr2 = address; /* Kernel addresses are always protection faults */ tsk->thread.error_code = error_code | (address >= TASK_SIZE); diff --git a/arch/x86_64/kernel/signal.c b/arch/x86_64/kernel/signal.c index 4886afcd628..739175b01e0 100644 --- a/arch/x86_64/kernel/signal.c +++ b/arch/x86_64/kernel/signal.c @@ -487,7 +487,7 @@ do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags) void signal_fault(struct pt_regs *regs, void __user *frame, char *where) { struct task_struct *me = current; - if (exception_trace) + if (show_unhandled_signals && printk_ratelimit()) printk("%s[%d] bad frame in %s frame:%p rip:%lx rsp:%lx orax:%lx\n", me->comm,me->pid,where,frame,regs->rip,regs->rsp,regs->orig_rax); diff --git a/arch/x86_64/kernel/traps.c b/arch/x86_64/kernel/traps.c index 8713ad4a4db..03888420775 100644 --- a/arch/x86_64/kernel/traps.c +++ b/arch/x86_64/kernel/traps.c @@ -584,7 +584,8 @@ static void __kprobes do_trap(int trapnr, int signr, char *str, tsk->thread.error_code = error_code; tsk->thread.trap_no = trapnr; - if (exception_trace && unhandled_signal(tsk, signr)) + if (show_unhandled_signals && unhandled_signal(tsk, signr) && + printk_ratelimit()) printk(KERN_INFO "%s[%d] trap %s rip:%lx rsp:%lx error:%lx\n", tsk->comm, tsk->pid, str, @@ -688,7 +689,8 @@ asmlinkage void __kprobes do_general_protection(struct pt_regs * regs, tsk->thread.error_code = error_code; tsk->thread.trap_no = 13; - if (exception_trace && unhandled_signal(tsk, SIGSEGV)) + if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) && + printk_ratelimit()) printk(KERN_INFO "%s[%d] general protection rip:%lx rsp:%lx error:%lx\n", tsk->comm, tsk->pid, diff --git a/arch/x86_64/mm/fault.c b/arch/x86_64/mm/fault.c index 2074bddd4f0..5e9ac70c135 100644 --- a/arch/x86_64/mm/fault.c +++ b/arch/x86_64/mm/fault.c @@ -221,16 +221,6 @@ static int is_errata93(struct pt_regs *regs, unsigned long address) return 0; } -int unhandled_signal(struct task_struct *tsk, int sig) -{ - if (is_init(tsk)) - return 1; - if (tsk->ptrace & PT_PTRACED) - return 0; - return (tsk->sighand->action[sig-1].sa.sa_handler == SIG_IGN) || - (tsk->sighand->action[sig-1].sa.sa_handler == SIG_DFL); -} - static noinline void pgtable_bad(unsigned long address, struct pt_regs *regs, unsigned long error_code) { @@ -302,7 +292,7 @@ static int vmalloc_fault(unsigned long address) } static int page_fault_trace; -int exception_trace = 1; +int show_unhandled_signals = 1; /* * This routine handles page faults. It determines the address, @@ -494,7 +484,8 @@ bad_area_nosemaphore: (address >> 32)) return; - if (exception_trace && unhandled_signal(tsk, SIGSEGV)) { + if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) && + printk_ratelimit()) { printk( "%s%s[%d]: segfault at %016lx rip %016lx rsp %016lx error %lx\n", tsk->pid > 1 ? KERN_INFO : KERN_EMERG, diff --git a/arch/x86_64/mm/init.c b/arch/x86_64/mm/init.c index 381c2ecd407..88678e82e23 100644 --- a/arch/x86_64/mm/init.c +++ b/arch/x86_64/mm/init.c @@ -697,39 +697,6 @@ int kern_addr_valid(unsigned long addr) return pfn_valid(pte_pfn(*pte)); } -#ifdef CONFIG_SYSCTL -#include - -static ctl_table debug_table2[] = { - { - .ctl_name = 99, - .procname = "exception-trace", - .data = &exception_trace, - .maxlen = sizeof(int), - .mode = 0644, - .proc_handler = proc_dointvec - }, - {} -}; - -static ctl_table debug_root_table2[] = { - { - .ctl_name = CTL_DEBUG, - .procname = "debug", - .mode = 0555, - .child = debug_table2 - }, - {} -}; - -static __init int x8664_sysctl_init(void) -{ - register_sysctl_table(debug_root_table2); - return 0; -} -__initcall(x8664_sysctl_init); -#endif - /* A pseudo VMA to allow ptrace access for the vsyscall page. This only covers the 64bit vsyscall page now. 32bit has a real VMA now and does not need special handling anymore. */ diff --git a/include/asm-x86_64/proto.h b/include/asm-x86_64/proto.h index d6e3225549c..31f20ad6587 100644 --- a/include/asm-x86_64/proto.h +++ b/include/asm-x86_64/proto.h @@ -75,8 +75,6 @@ extern void setup_node_bootmem(int nodeid, unsigned long start, unsigned long en extern void early_quirks(void); extern void check_efer(void); -extern int unhandled_signal(struct task_struct *tsk, int sig); - extern void select_idle_routine(const struct cpuinfo_x86 *c); extern unsigned long table_start, table_end; diff --git a/include/linux/signal.h b/include/linux/signal.h index ea91abe740d..0ae33886624 100644 --- a/include/linux/signal.h +++ b/include/linux/signal.h @@ -237,12 +237,15 @@ extern int group_send_sig_info(int sig, struct siginfo *info, struct task_struct extern int __group_send_sig_info(int, struct siginfo *, struct task_struct *); extern long do_sigpending(void __user *, unsigned long); extern int sigprocmask(int, sigset_t *, sigset_t *); +extern int show_unhandled_signals; struct pt_regs; extern int get_signal_to_deliver(siginfo_t *info, struct k_sigaction *return_ka, struct pt_regs *regs, void *cookie); extern struct kmem_cache *sighand_cachep; +int unhandled_signal(struct task_struct *tsk, int sig); + /* * In POSIX a signal is sent either to a specific thread (Linux task) * or to the process as a whole (Linux thread group). How the signal diff --git a/kernel/signal.c b/kernel/signal.c index 39d122753ba..ef8156a6aad 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -255,6 +255,16 @@ flush_signal_handlers(struct task_struct *t, int force_default) } } +int unhandled_signal(struct task_struct *tsk, int sig) +{ + if (is_init(tsk)) + return 1; + if (tsk->ptrace & PT_PTRACED) + return 0; + return (tsk->sighand->action[sig-1].sa.sa_handler == SIG_IGN) || + (tsk->sighand->action[sig-1].sa.sa_handler == SIG_DFL); +} + /* Notify the system that a driver wants to block all signals for this * process, and wants to be notified if any signals at all were to be diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 222299844ad..ddebf3f2aff 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -1203,6 +1203,16 @@ static ctl_table fs_table[] = { }; static ctl_table debug_table[] = { +#ifdef CONFIG_X86 + { + .ctl_name = CTL_UNNUMBERED, + .procname = "exception-trace", + .data = &show_unhandled_signals, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec + }, +#endif { .ctl_name = 0 } };