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fs.v6.3

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Merge tag 'fs.v6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/idmapping

Pull vfs hardening update from Christian Brauner:
 "Jan pointed out that during shutdown both filp_close() and super block
  destruction will use basic printk logging when bugs are detected. This
  causes issues in a few scenarios:

   - Tools like syzkaller cannot figure out that the logged message
     indicates a bug.

   - Users that explicitly opt in to have the kernel bug on data
     corruption by selecting CONFIG_BUG_ON_DATA_CORRUPTION should see
     the kernel crash when they did actually select that option.

   - When there are busy inodes after the superblock is shut down later
     access to such a busy inodes walks through freed memory. It would
     be better to cleanly crash instead.

  All of this can be addressed by using the already existing
  CHECK_DATA_CORRUPTION() macro in these places when kernel bugs are
  detected. Its logging improvement is useful for all users.

  Otherwise this only has a meaningful behavioral effect when users do
  select CONFIG_BUG_ON_DATA_CORRUPTION which means this is backward
  compatible for regular users"

* tag 'fs.v6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/idmapping:
  fs: Use CHECK_DATA_CORRUPTION() when kernel bugs are detected
This commit is contained in:
Linus Torvalds 2023-02-20 12:03:55 -08:00
commit ea5aac6fae
3 changed files with 23 additions and 6 deletions
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5
fs/open.c
View File

@ -1413,8 +1413,9 @@ int filp_close(struct file *filp, fl_owner_t id)
{
int retval = 0;
if (!file_count(filp)) {
printk(KERN_ERR "VFS: Close: file count is 0\n");
if (CHECK_DATA_CORRUPTION(file_count(filp) == 0,
"VFS: Close: file count is 0 (f_op=%ps)",
filp->f_op)) {
return 0;
}

21
fs/super.c
View File

@ -491,10 +491,23 @@ void generic_shutdown_super(struct super_block *sb)
if (sop->put_super)
sop->put_super(sb);
if (!list_empty(&sb->s_inodes)) {
printk("VFS: Busy inodes after unmount of %s. "
"Self-destruct in 5 seconds. Have a nice day...\n",
sb->s_id);
if (CHECK_DATA_CORRUPTION(!list_empty(&sb->s_inodes),
"VFS: Busy inodes after unmount of %s (%s)",
sb->s_id, sb->s_type->name)) {
/*
* Adding a proper bailout path here would be hard, but
* we can at least make it more likely that a later
* iput_final() or such crashes cleanly.
*/
struct inode *inode;
spin_lock(&sb->s_inode_list_lock);
list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
inode->i_op = VFS_PTR_POISON;
inode->i_sb = VFS_PTR_POISON;
inode->i_mapping = VFS_PTR_POISON;
}
spin_unlock(&sb->s_inode_list_lock);
}
}
spin_lock(&sb_lock);

3
include/linux/poison.h
View File

@ -84,4 +84,7 @@
/********** kernel/bpf/ **********/
#define BPF_PTR_POISON ((void *)(0xeB9FUL + POISON_POINTER_DELTA))
/********** VFS **********/
#define VFS_PTR_POISON ((void *)(0xF5 + POISON_POINTER_DELTA))
#endif