ptrace: compat_ptrace_request siginfo

This adds support for PTRACE_GETSIGINFO and PTRACE_SETSIGINFO in
compat_ptrace_request.  It relies on existing arch definitions for
copy_siginfo_to_user32 and copy_siginfo_from_user32.

On powerpc, this fixes a longstanding regression of 32-bit ptrace
calls on 64-bit kernels vs native calls (64-bit calls or 32-bit
kernels).  This can be seen in a 32-bit call using PTRACE_GETSIGINFO
to examine e.g. siginfo_t.si_addr from a signal that sets it.
(This was broken as of 2.6.24 and, I presume, many or all prior versions.)

Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 35 insertions, 13 deletions

diff --git a/kernel/ptrace.c b/kernel/ptrace.c
index fdb34e86f923..67e392ed5496 100644
--- a/kernel/ptrace.c
+++ b/kernel/ptrace.c
@@ -323,9 +323,8 @@ static int ptrace_setoptions(struct task_struct *child, long data)
         return (data & ~PTRACE_O_MASK) ? -EINVAL : 0;
 }
 
-static int ptrace_getsiginfo(struct task_struct *child, siginfo_t __user * data)
+static int ptrace_getsiginfo(struct task_struct *child, siginfo_t *info)
 {
-        siginfo_t lastinfo;
         int error = -ESRCH;
 
         read_lock(&tasklist_lock);
@@ -333,31 +332,25 @@ static int ptrace_getsiginfo(struct task_struct *child, siginfo_t __user * data)
                 error = -EINVAL;
                 spin_lock_irq(&child->sighand->siglock);
                 if (likely(child->last_siginfo != NULL)) {
-                        lastinfo = *child->last_siginfo;
+                        *info = *child->last_siginfo;
                         error = 0;
                 }
                 spin_unlock_irq(&child->sighand->siglock);
         }
         read_unlock(&tasklist_lock);
-        if (!error)
-                return copy_siginfo_to_user(data, &lastinfo);
         return error;
 }
 
-static int ptrace_setsiginfo(struct task_struct *child, siginfo_t __user * data)
+static int ptrace_setsiginfo(struct task_struct *child, const siginfo_t *info)
 {
-        siginfo_t newinfo;
         int error = -ESRCH;
 
-        if (copy_from_user(&newinfo, data, sizeof (siginfo_t)))
-                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;
+                        *child->last_siginfo = *info;
                         error = 0;
                 }
                 spin_unlock_irq(&child->sighand->siglock);
@@ -424,6 +417,7 @@ int ptrace_request(struct task_struct *child, long request,
                    long addr, long data)
 {
         int ret = -EIO;
+        siginfo_t siginfo;
 
         switch (request) {
         case PTRACE_PEEKTEXT:
@@ -442,12 +436,22 @@ int ptrace_request(struct task_struct *child, long request,
         case PTRACE_GETEVENTMSG:
                 ret = put_user(child->ptrace_message, (unsigned long __user *) data);
                 break;
+
         case PTRACE_GETSIGINFO:
-                ret = ptrace_getsiginfo(child, (siginfo_t __user *) data);
+                ret = ptrace_getsiginfo(child, &siginfo);
+                if (!ret)
+                        ret = copy_siginfo_to_user((siginfo_t __user *) data,
+                                                   &siginfo);
                 break;
+
         case PTRACE_SETSIGINFO:
-                ret = ptrace_setsiginfo(child, (siginfo_t __user *) data);
+                if (copy_from_user(&siginfo, (siginfo_t __user *) data,
+                                   sizeof siginfo))
+                        ret = -EFAULT;
+                else
+                        ret = ptrace_setsiginfo(child, &siginfo);
                 break;
+
         case PTRACE_DETACH:      /* detach a process that was attached. */
                 ret = ptrace_detach(child, data);
                 break;
@@ -616,6 +620,7 @@ int compat_ptrace_request(struct task_struct *child, compat_long_t request,
 {
         compat_ulong_t __user *datap = compat_ptr(data);
         compat_ulong_t word;
+        siginfo_t siginfo;
         int ret;
 
         switch (request) {
@@ -638,6 +643,23 @@ int compat_ptrace_request(struct task_struct *child, compat_long_t request,
                 ret = put_user((compat_ulong_t) child->ptrace_message, datap);
                 break;
 
+        case PTRACE_GETSIGINFO:
+                ret = ptrace_getsiginfo(child, &siginfo);
+                if (!ret)
+                        ret = copy_siginfo_to_user32(
+                                (struct compat_siginfo __user *) datap,
+                                &siginfo);
+                break;
+
+        case PTRACE_SETSIGINFO:
+                memset(&siginfo, 0, sizeof siginfo);
+                if (copy_siginfo_from_user32(
+                            &siginfo, (struct compat_siginfo __user *) datap))
+                        ret = -EFAULT;
+                else
+                        ret = ptrace_setsiginfo(child, &siginfo);
+                break;
+
         default:
                 ret = ptrace_request(child, request, addr, data);
         }