[PATCH] fault injection: process filtering for fault-injection capabilities

This patch provides process filtering feature.
The process filter allows failing only permitted processes
by /proc/<pid>/make-it-fail

Please see the example that demostrates how to inject slab allocation
failures into module init/cleanup code
in Documentation/fault-injection/fault-injection.txt

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

4 files changed, 86 insertions, 1 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index a3b5074118a7..fd959d5b5a80 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -853,6 +853,65 @@ static struct file_operations proc_seccomp_operations = {
 };
 #endif /* CONFIG_SECCOMP */
 
+#ifdef CONFIG_FAULT_INJECTION
+static ssize_t proc_fault_inject_read(struct file * file, char __user * buf,
+                                      size_t count, loff_t *ppos)
+{
+        struct task_struct *task = get_proc_task(file->f_dentry->d_inode);
+        char buffer[PROC_NUMBUF];
+        size_t len;
+        int make_it_fail;
+        loff_t __ppos = *ppos;
+
+        if (!task)
+                return -ESRCH;
+        make_it_fail = task->make_it_fail;
+        put_task_struct(task);
+
+        len = snprintf(buffer, sizeof(buffer), "%i\n", make_it_fail);
+        if (__ppos >= len)
+                return 0;
+        if (count > len-__ppos)
+                count = len-__ppos;
+        if (copy_to_user(buf, buffer + __ppos, count))
+                return -EFAULT;
+        *ppos = __ppos + count;
+        return count;
+}
+
+static ssize_t proc_fault_inject_write(struct file * file,
+                        const char __user * buf, size_t count, loff_t *ppos)
+{
+        struct task_struct *task;
+        char buffer[PROC_NUMBUF], *end;
+        int make_it_fail;
+
+        if (!capable(CAP_SYS_RESOURCE))
+                return -EPERM;
+        memset(buffer, 0, sizeof(buffer));
+        if (count > sizeof(buffer) - 1)
+                count = sizeof(buffer) - 1;
+        if (copy_from_user(buffer, buf, count))
+                return -EFAULT;
+        make_it_fail = simple_strtol(buffer, &end, 0);
+        if (*end == '\n')
+                end++;
+        task = get_proc_task(file->f_dentry->d_inode);
+        if (!task)
+                return -ESRCH;
+        task->make_it_fail = make_it_fail;
+        put_task_struct(task);
+        if (end - buffer == 0)
+                return -EIO;
+        return end - buffer;
+}
+
+static struct file_operations proc_fault_inject_operations = {
+        .read           = proc_fault_inject_read,
+        .write          = proc_fault_inject_write,
+};
+#endif
+
 static void *proc_pid_follow_link(struct dentry *dentry, struct nameidata *nd)
 {
         struct inode *inode = dentry->d_inode;
@@ -1793,6 +1852,9 @@ static struct pid_entry tgid_base_stuff[] = {
 #ifdef CONFIG_AUDITSYSCALL
         REG("loginuid",   S_IWUSR|S_IRUGO, loginuid),
 #endif
+#ifdef CONFIG_FAULT_INJECTION
+        REG("make-it-fail", S_IRUGO|S_IWUSR, fault_inject),
+#endif
 };
 
 static int proc_tgid_base_readdir(struct file * filp,
@@ -2068,6 +2130,9 @@ static struct pid_entry tid_base_stuff[] = {
 #ifdef CONFIG_AUDITSYSCALL
         REG("loginuid",  S_IWUSR|S_IRUGO, loginuid),
 #endif
+#ifdef CONFIG_FAULT_INJECTION
+        REG("make-it-fail", S_IRUGO|S_IWUSR, fault_inject),
+#endif
 };
 
 static int proc_tid_base_readdir(struct file * filp,
diff --git a/include/linux/fault-inject.h b/include/linux/fault-inject.h
index 4df4902bc8d8..a525f9b9f015 100644
--- a/include/linux/fault-inject.h
+++ b/include/linux/fault-inject.h
@@ -17,6 +17,7 @@ struct fault_attr {
         atomic_t times;
         atomic_t space;
         unsigned long verbose;
+        u32 task_filter;
 
         unsigned long count;
 
@@ -30,6 +31,7 @@ struct fault_attr {
                 struct dentry *times_file;
                 struct dentry *space_file;
                 struct dentry *verbose_file;
+                struct dentry *task_filter_file;
         } dentries;
 
 #endif
diff --git a/include/linux/sched.h b/include/linux/sched.h
index f0317edea141..ad9c46071ff8 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1045,6 +1045,9 @@ struct task_struct {
 #ifdef  CONFIG_TASK_DELAY_ACCT
         struct task_delay_info *delays;
 #endif
+#ifdef CONFIG_FAULT_INJECTION
+        int make_it_fail;
+#endif
 };
 
 static inline pid_t process_group(struct task_struct *tsk)
diff --git a/lib/fault-inject.c b/lib/fault-inject.c
index a7cb3afd132a..03468609d701 100644
--- a/lib/fault-inject.c
+++ b/lib/fault-inject.c
@@ -5,6 +5,7 @@
 #include <linux/types.h>
 #include <linux/fs.h>
 #include <linux/module.h>
+#include <linux/interrupt.h>
 #include <linux/fault-inject.h>
 
 /*
@@ -44,6 +45,11 @@ static void fail_dump(struct fault_attr *attr)
 
 #define atomic_dec_not_zero(v)          atomic_add_unless((v), -1, 0)
 
+static int fail_task(struct fault_attr *attr, struct task_struct *task)
+{
+        return !in_interrupt() && task->make_it_fail;
+}
+
 /*
  * This code is stolen from failmalloc-1.0
  * http://www.nongnu.org/failmalloc/
@@ -51,6 +57,9 @@ static void fail_dump(struct fault_attr *attr)
 
 int should_fail(struct fault_attr *attr, ssize_t size)
 {
+        if (attr->task_filter && !fail_task(attr, current))
+                return 0;
+
         if (atomic_read(&attr->times) == 0)
                 return 0;
 
@@ -135,6 +144,9 @@ void cleanup_fault_attr_dentries(struct fault_attr *attr)
         debugfs_remove(attr->dentries.verbose_file);
         attr->dentries.verbose_file = NULL;
 
+        debugfs_remove(attr->dentries.task_filter_file);
+        attr->dentries.task_filter_file = NULL;
+
         if (attr->dentries.dir)
                 WARN_ON(!simple_empty(attr->dentries.dir));
 
@@ -169,9 +181,12 @@ int init_fault_attr_dentries(struct fault_attr *attr, const char *name)
         attr->dentries.verbose_file =
                 debugfs_create_ul("verbose", mode, dir, &attr->verbose);
 
+        attr->dentries.task_filter_file = debugfs_create_bool("task-filter",
+                                                mode, dir, &attr->task_filter);
+
         if (!attr->dentries.probability_file || !attr->dentries.interval_file
             || !attr->dentries.times_file || !attr->dentries.space_file
-            || !attr->dentries.verbose_file)
+            || !attr->dentries.verbose_file || !attr->dentries.task_filter_file)
                 goto fail;
 
         return 0;