Commit abd4f750 authored by Masoud Asgharifard Sharbiani's avatar Masoud Asgharifard Sharbiani Committed by Linus Torvalds

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: default avatarMasoud Sharbiani <masouds@google.com>
Signed-off-by: default avatarAndi Kleen <ak@suse.de>
[ 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: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5fa63fcc
......@@ -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;
}
......
......@@ -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;
......
......@@ -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);
......
......@@ -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);
......
......@@ -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,
......
......@@ -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,
......
......@@ -697,39 +697,6 @@ int kern_addr_valid(unsigned long addr)
return pfn_valid(pte_pfn(*pte));
}
#ifdef CONFIG_SYSCTL
#include <linux/sysctl.h>
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. */
......
......@@ -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;
......
......@@ -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
......
......@@ -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
......
......@@ -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 }
};
......
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