x86, ptrace: add buffer size checks

Pass the buffer size for (most) ptrace commands that pass user-allocated buffers and check that size before accessing the buffer. Unfortunately, PTRACE_BTS_GET already uses all 4 parameters.
Commands that access user buffers return the number of bytes or records read or written.

Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

2 files changed, 29 insertions, 10 deletions

diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 236528bec6eb..e19a91db9b35 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -591,6 +591,7 @@ static int ptrace_bts_clear(struct task_struct *child)
 }
 
 static int ptrace_bts_drain(struct task_struct *child,
+                            long size,
                             struct bts_struct __user *out)
 {
         int end, i;
@@ -603,6 +604,9 @@ static int ptrace_bts_drain(struct task_struct *child,
         if (end <= 0)
                 return end;
 
+        if (size < (end * sizeof(struct bts_struct)))
+                return -EIO;
+
         for (i = 0; i < end; i++, out++) {
                 struct bts_struct ret;
                 int retval;
@@ -617,7 +621,7 @@ static int ptrace_bts_drain(struct task_struct *child,
 
         ds_clear(ds);
 
-        return i;
+        return end;
 }
 
 static int ptrace_bts_realloc(struct task_struct *child,
@@ -690,15 +694,22 @@ out:
 }
 
 static int ptrace_bts_config(struct task_struct *child,
+                             long cfg_size,
                              const struct ptrace_bts_config __user *ucfg)
 {
         struct ptrace_bts_config cfg;
         int bts_size, ret = 0;
         void *ds;
 
+        if (cfg_size < sizeof(cfg))
+                return -EIO;
+
         if (copy_from_user(&cfg, ucfg, sizeof(cfg)))
                 return -EFAULT;
 
+        if ((int)cfg.size < 0)
+                return -EINVAL;
+
         bts_size = 0;
         ds = (void *)child->thread.ds_area_msr;
         if (ds) {
@@ -734,6 +745,8 @@ static int ptrace_bts_config(struct task_struct *child,
         else
                 clear_tsk_thread_flag(child, TIF_BTS_TRACE_TS);
 
+        ret = sizeof(cfg);
+
 out:
         if (child->thread.debugctlmsr)
                 set_tsk_thread_flag(child, TIF_DEBUGCTLMSR);
@@ -749,11 +762,15 @@ errout:
 }
 
 static int ptrace_bts_status(struct task_struct *child,
+                             long cfg_size,
                              struct ptrace_bts_config __user *ucfg)
 {
         void *ds = (void *)child->thread.ds_area_msr;
         struct ptrace_bts_config cfg;
 
+        if (cfg_size < sizeof(cfg))
+                return -EIO;
+
         memset(&cfg, 0, sizeof(cfg));
 
         if (ds) {
@@ -923,12 +940,12 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data)
 
         case PTRACE_BTS_CONFIG:
                 ret = ptrace_bts_config
-                        (child, (struct ptrace_bts_config __user *)addr);
+                        (child, data, (struct ptrace_bts_config __user *)addr);
                 break;
 
         case PTRACE_BTS_STATUS:
                 ret = ptrace_bts_status
-                        (child, (struct ptrace_bts_config __user *)addr);
+                        (child, data, (struct ptrace_bts_config __user *)addr);
                 break;
 
         case PTRACE_BTS_SIZE:
@@ -946,7 +963,7 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data)
 
         case PTRACE_BTS_DRAIN:
                 ret = ptrace_bts_drain
-                        (child, (struct bts_struct __user *) addr);
+                        (child, data, (struct bts_struct __user *) addr);
                 break;
 
         default:
diff --git a/include/asm-x86/ptrace-abi.h b/include/asm-x86/ptrace-abi.h
index 32fe137822bf..bcf67044754c 100644
--- a/include/asm-x86/ptrace-abi.h
+++ b/include/asm-x86/ptrace-abi.h
@@ -99,13 +99,15 @@ struct ptrace_bts_config {
 
 #define PTRACE_BTS_CONFIG       40
 /* Configure branch trace recording.
-   DATA is ignored, ADDR points to a struct ptrace_bts_config.
+   ADDR points to a struct ptrace_bts_config.
+   DATA gives the size of that buffer.
    A new buffer is allocated, iff the size changes.
+   Returns the number of bytes read.
 */
 #define PTRACE_BTS_STATUS       41
-/* Return the current configuration.
-   DATA is ignored, ADDR points to a struct ptrace_bts_config
-   that will contain the result.
+/* Return the current configuration in a struct ptrace_bts_config
+   pointed to by ADDR; DATA gives the size of that buffer.
+   Returns the number of bytes written.
 */
 #define PTRACE_BTS_SIZE         42
 /* Return the number of available BTS records.
@@ -123,8 +125,8 @@ struct ptrace_bts_config {
 */
 #define PTRACE_BTS_DRAIN        45
 /* Read all available BTS records and clear the buffer.
-   DATA is ignored. ADDR points to an array of struct bts_struct of
-   suitable size.
+   ADDR points to an array of struct bts_struct.
+   DATA gives the size of that buffer.
    BTS records are read from oldest to newest.
    Returns number of BTS records drained.
 */