net/core/skb_fault_injection.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2
   3 #include <linux/debugfs.h>
   4 #include <linux/fault-inject.h>
   5 #include <linux/netdevice.h>
   6 #include <linux/skbuff.h>
   7
   8 static struct {
   9         struct fault_attr attr;
  10         char devname[IFNAMSIZ];
  11         bool filtered;
  12 } skb_realloc = {
  13         .attr = FAULT_ATTR_INITIALIZER,
  14         .filtered = false,
  15 };
  16
  17 static bool should_fail_net_realloc_skb(struct sk_buff *skb)
  18 {
  19         struct net_device *net = skb->dev;
  20
  21         if (skb_realloc.filtered &&
  22             strncmp(net->name, skb_realloc.devname, IFNAMSIZ))
  23                 /* device name filter set, but names do not match */
  24                 return false;
  25
  26         if (!should_fail(&skb_realloc.attr, 1))
  27                 return false;
  28
  29         return true;
  30 }
  31 ALLOW_ERROR_INJECTION(should_fail_net_realloc_skb, TRUE);
  32
  33 void skb_might_realloc(struct sk_buff *skb)
  34 {
  35         if (!should_fail_net_realloc_skb(skb))
  36                 return;
  37
  38         pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
  39 }
  40 EXPORT_SYMBOL(skb_might_realloc);
  41
  42 static int __init fail_skb_realloc_setup(char *str)
  43 {
  44         return setup_fault_attr(&skb_realloc.attr, str);
  45 }
  46 __setup("fail_skb_realloc=", fail_skb_realloc_setup);
  47
  48 static void reset_settings(void)
  49 {
  50         skb_realloc.filtered = false;
  51         memset(&skb_realloc.devname, 0, IFNAMSIZ);
  52 }
  53
  54 static ssize_t devname_write(struct file *file, const char __user *buffer,
  55                              size_t count, loff_t *ppos)
  56 {
  57         ssize_t ret;
  58
  59         reset_settings();
  60         ret = simple_write_to_buffer(&skb_realloc.devname, IFNAMSIZ,
  61                                      ppos, buffer, count);
  62         if (ret < 0)
  63                 return ret;
  64
  65         skb_realloc.devname[IFNAMSIZ - 1] = '\0';
  66         /* Remove a possible \n at the end of devname */
  67         strim(skb_realloc.devname);
  68
  69         if (strnlen(skb_realloc.devname, IFNAMSIZ))
  70                 skb_realloc.filtered = true;
  71
  72         return count;
  73 }
  74
  75 static ssize_t devname_read(struct file *file,
  76                             char __user *buffer,
  77                             size_t size, loff_t *ppos)
  78 {
  79         if (!skb_realloc.filtered)
  80                 return 0;
  81
  82         return simple_read_from_buffer(buffer, size, ppos, &skb_realloc.devname,
  83                                        strlen(skb_realloc.devname));
  84 }
  85
  86 static const struct file_operations devname_ops = {
  87         .write = devname_write,
  88         .read = devname_read,
  89 };
  90
  91 static int __init fail_skb_realloc_debugfs(void)
  92 {
  93         umode_t mode = S_IFREG | 0600;
  94         struct dentry *dir;
  95
  96         dir = fault_create_debugfs_attr("fail_skb_realloc", NULL,
  97                                         &skb_realloc.attr);
  98         if (IS_ERR(dir))
  99                 return PTR_ERR(dir);
 100
 101         debugfs_create_file("devname", mode, dir, NULL, &devname_ops);
 102
 103         return 0;
 104 }
 105
 106 late_initcall(fail_skb_realloc_debugfs);