Make i386 kernel show the unhandled signals
PATCH 1/1 Make i386 kernel show the unhandled signals
Hello,
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 different kernels. Like x86_64, it can be disabled by setting debug.show_unhandled_signals sysctl variable to 0 (or by doing echo 0 > /proc/sys/debug/show_unhandled_signals)
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;
}cheers,
Masoud
Signed-off-by Masoud Sharbiani <[email protected]>
arch/i386/kernel/signal.c | 5 +++++ arch/i386/kernel/traps.c | 7 +++++++ arch/i386/mm/fault.c | 11 +++++++++++ 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 | 35 ----------------------------------- include/asm-x86_64/proto.h | 2 -- include/linux/signal.h | 3 +++ include/linux/sysctl.h | 3 +++ kernel/signal.c | 10 ++++++++++ kernel/sysctl.c | 10 ++++++++++ 12 files changed, 57 insertions(+), 52 deletions(-)
arch/i386/kernel/signal.c +5 -0
@@ -199,6 +199,11 @@ asmlinkage int sys_sigreturn(unsigned long __unused)return eax; badframe: +if (show_unhandled_signals &&printk_ratelimit ()) +printk ("%s[%d] bad frame in sigreturn frame:%p eip:%lx esp:%lx oeax:%lx\n" , + current->comm, current->pid, frame, regs->eip, regs->esp, + regs->orig_eax); +force_sig (SIGSEGV , current);return 0 ; }
arch/i386/kernel/traps.c +7 -0
@@ -610,6 +610,13 @@ 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 ;
arch/i386/mm/fault.c +11 -0
@@ -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
@@ -465,6 +467,15 @@ 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 );
arch/i386/mm/init.c +0 -0
arch/x86_64/kernel/signal.c +1 -1
@@ -480,7 +480,7 @@ 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);
arch/x86_64/kernel/traps.c +4 -2
@@ -577,7 +577,8 @@ 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,
@@ -681,7 +682,8 @@ 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,
arch/x86_64/mm/fault.c +3 -12
@@ -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) }int page_fault_trace =0 ; -int exception_trace =1 ; +int show_unhandled_signals =1 ;/* * This routine handles page faults. It determines the address,
@@ -489,7 +479,8 @@ 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,
arch/x86_64/mm/init.c +0 -35
@@ -690,41 +690,6 @@ int kern_addr_valid(unsigned long addr)return pfn_valid (pte_pfn (*pte)); } -#ifdef CONFIG_SYSCTL -#include <linux/sysctl.h> - -extern int exception_trace, page_fault_trace; - -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. */
include/asm-x86_64/proto.h +0 -2
@@ -75,8 +75,6 @@ extern void setup_node_bootmem(int nodeid, unsigned long start, unsigned long enextern 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;
include/linux/signal.h +3 -0
@@ -238,12 +238,15 @@ extern int group_send_sig_info(int sig, struct siginfo *info, struct task_structextern 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
include/linux/sysctl.h +3 -0
@@ -835,6 +835,9 @@ enum { };/* CTL_DEBUG names: */ +enum { +DEBUG_UNHANDLED_SIGNALS =1 , +};/* CTL_DEV names: */ enum {
kernel/signal.c +10 -0
@@ -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
kernel/sysctl.c +10 -0
@@ -1026,6 +1026,16 @@ static ctl_table fs_table[] = { }; static ctl_table debug_table[] = { +#ifdef CONFIG_X86 + { + .ctl_name = DEBUG_UNHANDLED_SIGNALS, + .procname = "show-unhandled-signals", + .data = &show_unhandled_signals, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec + }, +#endif { .ctl_name = 0 } };