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parisc: fix kernel crash when unwinding a userspace process

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Any user on existing parisc 32- and 64bit-kernels can easily crash
the kernel and as such enforce a DSO.
A simple testcase is available here:
        http://gsyprf10.external.hp.com/~deller/crash.tgz

The problem is introduced by the fact, that the handle_interruption()
crash handler calls the show_regs() function, which in turn tries to
unwind the stack by calling parisc_show_stack().  Since the stack contains
userspace addresses, a try to unwind the stack is dangerous and useless
and leads to the crash.

The fix is trivial: For userspace processes
a) avoid to unwind the stack, and
b) avoid to resolve userspace addresses to kernel symbol names.

While touching this code, I converted print_symbol() to %pS
printk formats and made parisc_show_stack() static.

An initial patch for this was written by Kyle McMartin back in August:
http://marc.info/?l=linux-parisc&m=121805168830283&w=2

Compile and run-tested with a 64bit parisc kernel.

Signed-off-by: Helge Deller <deller@gmx.de>
Cc: Grant Grundler <grundler@parisc-linux.org>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: <stable@kernel.org>		[2.6.25.x, 2.6.26.x, 2.6.27.x, earlier...]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Kyle McMartin <kyle@mcmartin.ca>
This commit is contained in:
Helge Deller 2008-11-26 12:46:22 -08:00 committed by Kyle McMartin
parent 9860d1b08b
commit 7a3f5134a8
1 changed files with 20 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

41
arch/parisc/kernel/traps.c
View File

@ -24,7 +24,6 @@
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/console.h>
#include <linux/kallsyms.h>
#include <linux/bug.h>
#include <asm/assembly.h>
@ -51,7 +50,7 @@
DEFINE_SPINLOCK(pa_dbit_lock);
#endif
void parisc_show_stack(struct task_struct *t, unsigned long *sp,
static void parisc_show_stack(struct task_struct *task, unsigned long *sp,
struct pt_regs *regs);
static int printbinary(char *buf, unsigned long x, int nbits)
@ -121,18 +120,19 @@ static void print_fr(char *level, struct pt_regs *regs)
void show_regs(struct pt_regs *regs)
{
int i;
int i, user;
char *level;
unsigned long cr30, cr31;
level = user_mode(regs) ? KERN_DEBUG : KERN_CRIT;
user = user_mode(regs);
level = user ? KERN_DEBUG : KERN_CRIT;
print_gr(level, regs);
for (i = 0; i < 8; i += 4)
PRINTREGS(level, regs->sr, "sr", RFMT, i);
if (user_mode(regs))
if (user)
print_fr(level, regs);
cr30 = mfctl(30);
@ -145,14 +145,18 @@ void show_regs(struct pt_regs *regs)
printk("%s CPU: %8d CR30: " RFMT " CR31: " RFMT "\n",
level, current_thread_info()->cpu, cr30, cr31);
printk("%s ORIG_R28: " RFMT "\n", level, regs->orig_r28);
printk(level);
print_symbol(" IAOQ[0]: %s\n", regs->iaoq[0]);
printk(level);
print_symbol(" IAOQ[1]: %s\n", regs->iaoq[1]);
printk(level);
print_symbol(" RP(r2): %s\n", regs->gr[2]);
parisc_show_stack(current, NULL, regs);
if (user) {
printk("%s IAOQ[0]: " RFMT "\n", level, regs->iaoq[0]);
printk("%s IAOQ[1]: " RFMT "\n", level, regs->iaoq[1]);
printk("%s RP(r2): " RFMT "\n", level, regs->gr[2]);
} else {
printk("%s IAOQ[0]: %pS\n", level, (void *) regs->iaoq[0]);
printk("%s IAOQ[1]: %pS\n", level, (void *) regs->iaoq[1]);
printk("%s RP(r2): %pS\n", level, (void *) regs->gr[2]);
parisc_show_stack(current, NULL, regs);
}
}
@ -173,20 +177,15 @@ static void do_show_stack(struct unwind_frame_info *info)
break;
if (__kernel_text_address(info->ip)) {
printk("%s [<" RFMT ">] ", (i&0x3)==1 ? KERN_CRIT : "", info->ip);
#ifdef CONFIG_KALLSYMS
print_symbol("%s\n", info->ip);
#else
if ((i & 0x03) == 0)
printk("\n");
#endif
printk(KERN_CRIT " [<" RFMT ">] %pS\n",
info->ip, (void *) info->ip);
i++;
}
}
printk("\n");
printk(KERN_CRIT "\n");
}
void parisc_show_stack(struct task_struct *task, unsigned long *sp,
static void parisc_show_stack(struct task_struct *task, unsigned long *sp,
struct pt_regs *regs)
{
struct unwind_frame_info info;