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Subject[patch] x86_64: fix compat mode ptrace() bug
ptrace(PTRACE_[GS]ETSIGINFO) is broken in ia32 mode on 64-bit kernel,
as reported by Albert Cahalan.

Below patch fixes it; should the new code be moved to kernel/compat.c?
I only added it to x86_64 for now; it was copied from kernel/ptrace.c
with minor changes.

Test program:

/* ptrace() test program: does tracer get the correct pid and uid?
* Run this test in 32-bit compat environment on 64-bit kernel.
*/
#define _GNU_SOURCE
#include <stdio.h>
#include <unistd.h>
#include <sys/ptrace.h>
#include <linux/ptrace.h>
#include <sys/wait.h>

static void handler(int nr, siginfo_t *si, void *vuc)
{
printf("child %u in signal handler: signal %d from pid %d, uid %d\n",
getpid(), si->si_signo, si->si_pid, si->si_uid);
}

static void do_child()
{
struct sigaction sa = {
.sa_sigaction = handler,
.sa_flags = SA_SIGINFO,
};
sigaction(SIGUSR1, &sa, NULL);
ptrace(PTRACE_TRACEME, 0, 0, 0);
kill(getpid(), SIGUSR1);
}

static void do_parent()
{
int children = 1, child, status;
siginfo_t si;
again:
child = wait(&status);
if (WIFSTOPPED(status)) {
unsigned int signo = WSTOPSIG(status) & 0x7f;
ptrace(PTRACE_GETSIGINFO, child, 0, &si);
fprintf(stderr, "child %u stopped in parent: signal %u from pid %d, uid %d\n",
child, signo, si.si_pid, si.si_uid);
ptrace(PTRACE_CONT, child, NULL, (void *)signo);
}
if (!WIFEXITED(status) && !(WIFSIGNALED(status)))
goto again;
fprintf(stderr, "child %u gone\n", child);
if (--children > 0)
goto again;
fprintf(stderr, "exiting: no children left\n");
}


int main(int argc, char * const argv[])
{
if (fork())
do_parent();
else
do_child();

return 0;
}


arch/x86_64/ia32/ptrace32.c | 60 ++++++++++++++++++++++++++++++++++++++++++--
1 files changed, 58 insertions(+), 2 deletions(-)

--- 2.6.17-rc6-64.orig/arch/x86_64/ia32/ptrace32.c
+++ 2.6.17-rc6-64/arch/x86_64/ia32/ptrace32.c
@@ -18,6 +18,7 @@
#include <linux/unistd.h>
#include <linux/mm.h>
#include <linux/ptrace.h>
+#include <linux/compat.h>
#include <asm/ptrace.h>
#include <asm/compat.h>
#include <asm/uaccess.h>
@@ -199,6 +200,51 @@ static int getreg32(struct task_struct *

#undef R32

+static int compat_ptrace_getsiginfo(struct task_struct *child,
+ struct compat_siginfo __user *data)
+{
+ siginfo_t lastinfo;
+ int error = -ESRCH;
+
+ read_lock(&tasklist_lock);
+ if (likely(child->sighand != NULL)) {
+ error = -EINVAL;
+ spin_lock_irq(&child->sighand->siglock);
+ if (likely(child->last_siginfo != NULL)) {
+ lastinfo = *child->last_siginfo;
+ error = 0;
+ }
+ spin_unlock_irq(&child->sighand->siglock);
+ }
+ read_unlock(&tasklist_lock);
+ if (!error)
+ return copy_siginfo_to_user32(data, &lastinfo);
+ return error;
+}
+
+static int compat_ptrace_setsiginfo(struct task_struct *child,
+ struct compat_siginfo __user *data)
+{
+ siginfo_t newinfo;
+ int error = -ESRCH;
+
+ if (copy_siginfo_from_user32(&newinfo, data))
+ return -EFAULT;
+
+ read_lock(&tasklist_lock);
+ if (likely(child->sighand != NULL)) {
+ error = -EINVAL;
+ spin_lock_irq(&child->sighand->siglock);
+ if (likely(child->last_siginfo != NULL)) {
+ *child->last_siginfo = newinfo;
+ error = 0;
+ }
+ spin_unlock_irq(&child->sighand->siglock);
+ }
+ read_unlock(&tasklist_lock);
+ return error;
+}
+
asmlinkage long sys32_ptrace(long request, u32 pid, u32 addr, u32 data)
{
struct task_struct *child;
@@ -207,7 +253,7 @@ asmlinkage long sys32_ptrace(long reques
int ret;
__u32 val;

- switch (request) {
+ switch (request) {
default:
return sys_ptrace(request, pid, addr, data);

@@ -223,6 +269,8 @@ asmlinkage long sys32_ptrace(long reques
case PTRACE_GETFPREGS:
case PTRACE_SETFPXREGS:
case PTRACE_GETFPXREGS:
+ case PTRACE_GETSIGINFO:
+ case PTRACE_SETSIGINFO:
case PTRACE_GETEVENTMSG:
break;
}
@@ -344,8 +392,16 @@ asmlinkage long sys32_ptrace(long reques
break;
}

+ case PTRACE_GETSIGINFO:
+ ret = compat_ptrace_getsiginfo(child, datap);
+ break;
+
+ case PTRACE_SETSIGINFO:
+ ret = compat_ptrace_setsiginfo(child, datap);
+ break;
+
case PTRACE_GETEVENTMSG:
- ret = put_user(child->ptrace_message,(unsigned int __user *)compat_ptr(data));
+ ret = put_user(child->ptrace_message, (unsigned int __user *)datap);
break;

default:
--
Chuck
-
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