Revision 0ace17d56824165c7f4c68785d6b58971db954dd authored by Richard Palethorpe on 21 January 2020, 13:42:58 UTC, committed by David S. Miller on 22 January 2020, 19:32:03 UTC
write_wakeup can happen in parallel with close/hangup where tty->disc_data is set to NULL and the netdevice is freed thus also freeing disc_data. write_wakeup accesses disc_data so we must prevent close from freeing the netdev while write_wakeup has a non-NULL view of tty->disc_data. We also need to make sure that accesses to disc_data are atomic. Which can all be done with RCU. This problem was found by Syzkaller on SLCAN, but the same issue is reproducible with the SLIP line discipline using an LTP test based on the Syzkaller reproducer. A fix which didn't use RCU was posted by Hillf Danton. Fixes: 661f7fda21b1 ("slip: Fix deadlock in write_wakeup") Fixes: a8e83b17536a ("slcan: Port write_wakeup deadlock fix from slip") Reported-by: syzbot+017e491ae13c0068598a@syzkaller.appspotmail.com Signed-off-by: Richard Palethorpe <rpalethorpe@suse.com> Cc: Wolfgang Grandegger <wg@grandegger.com> Cc: Marc Kleine-Budde <mkl@pengutronix.de> Cc: "David S. Miller" <davem@davemloft.net> Cc: Tyler Hall <tylerwhall@gmail.com> Cc: linux-can@vger.kernel.org Cc: netdev@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: syzkaller@googlegroups.com Signed-off-by: David S. Miller <davem@davemloft.net>
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bad_inode.c
// SPDX-License-Identifier: GPL-2.0
/*
* linux/fs/bad_inode.c
*
* Copyright (C) 1997, Stephen Tweedie
*
* Provide stub functions for unreadable inodes
*
* Fabian Frederick : August 2003 - All file operations assigned to EIO
*/
#include <linux/fs.h>
#include <linux/export.h>
#include <linux/stat.h>
#include <linux/time.h>
#include <linux/namei.h>
#include <linux/poll.h>
static int bad_file_open(struct inode *inode, struct file *filp)
{
return -EIO;
}
static const struct file_operations bad_file_ops =
{
.open = bad_file_open,
};
static int bad_inode_create (struct inode *dir, struct dentry *dentry,
umode_t mode, bool excl)
{
return -EIO;
}
static struct dentry *bad_inode_lookup(struct inode *dir,
struct dentry *dentry, unsigned int flags)
{
return ERR_PTR(-EIO);
}
static int bad_inode_link (struct dentry *old_dentry, struct inode *dir,
struct dentry *dentry)
{
return -EIO;
}
static int bad_inode_unlink(struct inode *dir, struct dentry *dentry)
{
return -EIO;
}
static int bad_inode_symlink (struct inode *dir, struct dentry *dentry,
const char *symname)
{
return -EIO;
}
static int bad_inode_mkdir(struct inode *dir, struct dentry *dentry,
umode_t mode)
{
return -EIO;
}
static int bad_inode_rmdir (struct inode *dir, struct dentry *dentry)
{
return -EIO;
}
static int bad_inode_mknod (struct inode *dir, struct dentry *dentry,
umode_t mode, dev_t rdev)
{
return -EIO;
}
static int bad_inode_rename2(struct inode *old_dir, struct dentry *old_dentry,
struct inode *new_dir, struct dentry *new_dentry,
unsigned int flags)
{
return -EIO;
}
static int bad_inode_readlink(struct dentry *dentry, char __user *buffer,
int buflen)
{
return -EIO;
}
static int bad_inode_permission(struct inode *inode, int mask)
{
return -EIO;
}
static int bad_inode_getattr(const struct path *path, struct kstat *stat,
u32 request_mask, unsigned int query_flags)
{
return -EIO;
}
static int bad_inode_setattr(struct dentry *direntry, struct iattr *attrs)
{
return -EIO;
}
static ssize_t bad_inode_listxattr(struct dentry *dentry, char *buffer,
size_t buffer_size)
{
return -EIO;
}
static const char *bad_inode_get_link(struct dentry *dentry,
struct inode *inode,
struct delayed_call *done)
{
return ERR_PTR(-EIO);
}
static struct posix_acl *bad_inode_get_acl(struct inode *inode, int type)
{
return ERR_PTR(-EIO);
}
static int bad_inode_fiemap(struct inode *inode,
struct fiemap_extent_info *fieinfo, u64 start,
u64 len)
{
return -EIO;
}
static int bad_inode_update_time(struct inode *inode, struct timespec64 *time,
int flags)
{
return -EIO;
}
static int bad_inode_atomic_open(struct inode *inode, struct dentry *dentry,
struct file *file, unsigned int open_flag,
umode_t create_mode)
{
return -EIO;
}
static int bad_inode_tmpfile(struct inode *inode, struct dentry *dentry,
umode_t mode)
{
return -EIO;
}
static int bad_inode_set_acl(struct inode *inode, struct posix_acl *acl,
int type)
{
return -EIO;
}
static const struct inode_operations bad_inode_ops =
{
.create = bad_inode_create,
.lookup = bad_inode_lookup,
.link = bad_inode_link,
.unlink = bad_inode_unlink,
.symlink = bad_inode_symlink,
.mkdir = bad_inode_mkdir,
.rmdir = bad_inode_rmdir,
.mknod = bad_inode_mknod,
.rename = bad_inode_rename2,
.readlink = bad_inode_readlink,
.permission = bad_inode_permission,
.getattr = bad_inode_getattr,
.setattr = bad_inode_setattr,
.listxattr = bad_inode_listxattr,
.get_link = bad_inode_get_link,
.get_acl = bad_inode_get_acl,
.fiemap = bad_inode_fiemap,
.update_time = bad_inode_update_time,
.atomic_open = bad_inode_atomic_open,
.tmpfile = bad_inode_tmpfile,
.set_acl = bad_inode_set_acl,
};
/*
* When a filesystem is unable to read an inode due to an I/O error in
* its read_inode() function, it can call make_bad_inode() to return a
* set of stubs which will return EIO errors as required.
*
* We only need to do limited initialisation: all other fields are
* preinitialised to zero automatically.
*/
/**
* make_bad_inode - mark an inode bad due to an I/O error
* @inode: Inode to mark bad
*
* When an inode cannot be read due to a media or remote network
* failure this function makes the inode "bad" and causes I/O operations
* on it to fail from this point on.
*/
void make_bad_inode(struct inode *inode)
{
remove_inode_hash(inode);
inode->i_mode = S_IFREG;
inode->i_atime = inode->i_mtime = inode->i_ctime =
current_time(inode);
inode->i_op = &bad_inode_ops;
inode->i_opflags &= ~IOP_XATTR;
inode->i_fop = &bad_file_ops;
}
EXPORT_SYMBOL(make_bad_inode);
/*
* This tests whether an inode has been flagged as bad. The test uses
* &bad_inode_ops to cover the case of invalidated inodes as well as
* those created by make_bad_inode() above.
*/
/**
* is_bad_inode - is an inode errored
* @inode: inode to test
*
* Returns true if the inode in question has been marked as bad.
*/
bool is_bad_inode(struct inode *inode)
{
return (inode->i_op == &bad_inode_ops);
}
EXPORT_SYMBOL(is_bad_inode);
/**
* iget_failed - Mark an under-construction inode as dead and release it
* @inode: The inode to discard
*
* Mark an under-construction inode as dead and release it.
*/
void iget_failed(struct inode *inode)
{
make_bad_inode(inode);
unlock_new_inode(inode);
iput(inode);
}
EXPORT_SYMBOL(iget_failed);
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