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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statfs.c
// SPDX-License-Identifier: GPL-2.0
#include <linux/syscalls.h>
#include <linux/export.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/statfs.h>
#include <linux/security.h>
#include <linux/uaccess.h>
#include <linux/compat.h>
#include "internal.h"
static int flags_by_mnt(int mnt_flags)
{
int flags = 0;
if (mnt_flags & MNT_READONLY)
flags |= ST_RDONLY;
if (mnt_flags & MNT_NOSUID)
flags |= ST_NOSUID;
if (mnt_flags & MNT_NODEV)
flags |= ST_NODEV;
if (mnt_flags & MNT_NOEXEC)
flags |= ST_NOEXEC;
if (mnt_flags & MNT_NOATIME)
flags |= ST_NOATIME;
if (mnt_flags & MNT_NODIRATIME)
flags |= ST_NODIRATIME;
if (mnt_flags & MNT_RELATIME)
flags |= ST_RELATIME;
return flags;
}
static int flags_by_sb(int s_flags)
{
int flags = 0;
if (s_flags & SB_SYNCHRONOUS)
flags |= ST_SYNCHRONOUS;
if (s_flags & SB_MANDLOCK)
flags |= ST_MANDLOCK;
if (s_flags & SB_RDONLY)
flags |= ST_RDONLY;
return flags;
}
static int calculate_f_flags(struct vfsmount *mnt)
{
return ST_VALID | flags_by_mnt(mnt->mnt_flags) |
flags_by_sb(mnt->mnt_sb->s_flags);
}
static int statfs_by_dentry(struct dentry *dentry, struct kstatfs *buf)
{
int retval;
if (!dentry->d_sb->s_op->statfs)
return -ENOSYS;
memset(buf, 0, sizeof(*buf));
retval = security_sb_statfs(dentry);
if (retval)
return retval;
retval = dentry->d_sb->s_op->statfs(dentry, buf);
if (retval == 0 && buf->f_frsize == 0)
buf->f_frsize = buf->f_bsize;
return retval;
}
int vfs_get_fsid(struct dentry *dentry, __kernel_fsid_t *fsid)
{
struct kstatfs st;
int error;
error = statfs_by_dentry(dentry, &st);
if (error)
return error;
*fsid = st.f_fsid;
return 0;
}
EXPORT_SYMBOL(vfs_get_fsid);
int vfs_statfs(const struct path *path, struct kstatfs *buf)
{
int error;
error = statfs_by_dentry(path->dentry, buf);
if (!error)
buf->f_flags = calculate_f_flags(path->mnt);
return error;
}
EXPORT_SYMBOL(vfs_statfs);
int user_statfs(const char __user *pathname, struct kstatfs *st)
{
struct path path;
int error;
unsigned int lookup_flags = LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT;
retry:
error = user_path_at(AT_FDCWD, pathname, lookup_flags, &path);
if (!error) {
error = vfs_statfs(&path, st);
path_put(&path);
if (retry_estale(error, lookup_flags)) {
lookup_flags |= LOOKUP_REVAL;
goto retry;
}
}
return error;
}
int fd_statfs(int fd, struct kstatfs *st)
{
struct fd f = fdget_raw(fd);
int error = -EBADF;
if (f.file) {
error = vfs_statfs(&f.file->f_path, st);
fdput(f);
}
return error;
}
static int do_statfs_native(struct kstatfs *st, struct statfs __user *p)
{
struct statfs buf;
if (sizeof(buf) == sizeof(*st))
memcpy(&buf, st, sizeof(*st));
else {
if (sizeof buf.f_blocks == 4) {
if ((st->f_blocks | st->f_bfree | st->f_bavail |
st->f_bsize | st->f_frsize) &
0xffffffff00000000ULL)
return -EOVERFLOW;
/*
* f_files and f_ffree may be -1; it's okay to stuff
* that into 32 bits
*/
if (st->f_files != -1 &&
(st->f_files & 0xffffffff00000000ULL))
return -EOVERFLOW;
if (st->f_ffree != -1 &&
(st->f_ffree & 0xffffffff00000000ULL))
return -EOVERFLOW;
}
buf.f_type = st->f_type;
buf.f_bsize = st->f_bsize;
buf.f_blocks = st->f_blocks;
buf.f_bfree = st->f_bfree;
buf.f_bavail = st->f_bavail;
buf.f_files = st->f_files;
buf.f_ffree = st->f_ffree;
buf.f_fsid = st->f_fsid;
buf.f_namelen = st->f_namelen;
buf.f_frsize = st->f_frsize;
buf.f_flags = st->f_flags;
memset(buf.f_spare, 0, sizeof(buf.f_spare));
}
if (copy_to_user(p, &buf, sizeof(buf)))
return -EFAULT;
return 0;
}
static int do_statfs64(struct kstatfs *st, struct statfs64 __user *p)
{
struct statfs64 buf;
if (sizeof(buf) == sizeof(*st))
memcpy(&buf, st, sizeof(*st));
else {
buf.f_type = st->f_type;
buf.f_bsize = st->f_bsize;
buf.f_blocks = st->f_blocks;
buf.f_bfree = st->f_bfree;
buf.f_bavail = st->f_bavail;
buf.f_files = st->f_files;
buf.f_ffree = st->f_ffree;
buf.f_fsid = st->f_fsid;
buf.f_namelen = st->f_namelen;
buf.f_frsize = st->f_frsize;
buf.f_flags = st->f_flags;
memset(buf.f_spare, 0, sizeof(buf.f_spare));
}
if (copy_to_user(p, &buf, sizeof(buf)))
return -EFAULT;
return 0;
}
SYSCALL_DEFINE2(statfs, const char __user *, pathname, struct statfs __user *, buf)
{
struct kstatfs st;
int error = user_statfs(pathname, &st);
if (!error)
error = do_statfs_native(&st, buf);
return error;
}
SYSCALL_DEFINE3(statfs64, const char __user *, pathname, size_t, sz, struct statfs64 __user *, buf)
{
struct kstatfs st;
int error;
if (sz != sizeof(*buf))
return -EINVAL;
error = user_statfs(pathname, &st);
if (!error)
error = do_statfs64(&st, buf);
return error;
}
SYSCALL_DEFINE2(fstatfs, unsigned int, fd, struct statfs __user *, buf)
{
struct kstatfs st;
int error = fd_statfs(fd, &st);
if (!error)
error = do_statfs_native(&st, buf);
return error;
}
SYSCALL_DEFINE3(fstatfs64, unsigned int, fd, size_t, sz, struct statfs64 __user *, buf)
{
struct kstatfs st;
int error;
if (sz != sizeof(*buf))
return -EINVAL;
error = fd_statfs(fd, &st);
if (!error)
error = do_statfs64(&st, buf);
return error;
}
static int vfs_ustat(dev_t dev, struct kstatfs *sbuf)
{
struct super_block *s = user_get_super(dev);
int err;
if (!s)
return -EINVAL;
err = statfs_by_dentry(s->s_root, sbuf);
drop_super(s);
return err;
}
SYSCALL_DEFINE2(ustat, unsigned, dev, struct ustat __user *, ubuf)
{
struct ustat tmp;
struct kstatfs sbuf;
int err = vfs_ustat(new_decode_dev(dev), &sbuf);
if (err)
return err;
memset(&tmp,0,sizeof(struct ustat));
tmp.f_tfree = sbuf.f_bfree;
tmp.f_tinode = sbuf.f_ffree;
return copy_to_user(ubuf, &tmp, sizeof(struct ustat)) ? -EFAULT : 0;
}
#ifdef CONFIG_COMPAT
static int put_compat_statfs(struct compat_statfs __user *ubuf, struct kstatfs *kbuf)
{
struct compat_statfs buf;
if (sizeof ubuf->f_blocks == 4) {
if ((kbuf->f_blocks | kbuf->f_bfree | kbuf->f_bavail |
kbuf->f_bsize | kbuf->f_frsize) & 0xffffffff00000000ULL)
return -EOVERFLOW;
/* f_files and f_ffree may be -1; it's okay
* to stuff that into 32 bits */
if (kbuf->f_files != 0xffffffffffffffffULL
&& (kbuf->f_files & 0xffffffff00000000ULL))
return -EOVERFLOW;
if (kbuf->f_ffree != 0xffffffffffffffffULL
&& (kbuf->f_ffree & 0xffffffff00000000ULL))
return -EOVERFLOW;
}
memset(&buf, 0, sizeof(struct compat_statfs));
buf.f_type = kbuf->f_type;
buf.f_bsize = kbuf->f_bsize;
buf.f_blocks = kbuf->f_blocks;
buf.f_bfree = kbuf->f_bfree;
buf.f_bavail = kbuf->f_bavail;
buf.f_files = kbuf->f_files;
buf.f_ffree = kbuf->f_ffree;
buf.f_namelen = kbuf->f_namelen;
buf.f_fsid.val[0] = kbuf->f_fsid.val[0];
buf.f_fsid.val[1] = kbuf->f_fsid.val[1];
buf.f_frsize = kbuf->f_frsize;
buf.f_flags = kbuf->f_flags;
if (copy_to_user(ubuf, &buf, sizeof(struct compat_statfs)))
return -EFAULT;
return 0;
}
/*
* The following statfs calls are copies of code from fs/statfs.c and
* should be checked against those from time to time
*/
COMPAT_SYSCALL_DEFINE2(statfs, const char __user *, pathname, struct compat_statfs __user *, buf)
{
struct kstatfs tmp;
int error = user_statfs(pathname, &tmp);
if (!error)
error = put_compat_statfs(buf, &tmp);
return error;
}
COMPAT_SYSCALL_DEFINE2(fstatfs, unsigned int, fd, struct compat_statfs __user *, buf)
{
struct kstatfs tmp;
int error = fd_statfs(fd, &tmp);
if (!error)
error = put_compat_statfs(buf, &tmp);
return error;
}
static int put_compat_statfs64(struct compat_statfs64 __user *ubuf, struct kstatfs *kbuf)
{
struct compat_statfs64 buf;
if ((kbuf->f_bsize | kbuf->f_frsize) & 0xffffffff00000000ULL)
return -EOVERFLOW;
memset(&buf, 0, sizeof(struct compat_statfs64));
buf.f_type = kbuf->f_type;
buf.f_bsize = kbuf->f_bsize;
buf.f_blocks = kbuf->f_blocks;
buf.f_bfree = kbuf->f_bfree;
buf.f_bavail = kbuf->f_bavail;
buf.f_files = kbuf->f_files;
buf.f_ffree = kbuf->f_ffree;
buf.f_namelen = kbuf->f_namelen;
buf.f_fsid.val[0] = kbuf->f_fsid.val[0];
buf.f_fsid.val[1] = kbuf->f_fsid.val[1];
buf.f_frsize = kbuf->f_frsize;
buf.f_flags = kbuf->f_flags;
if (copy_to_user(ubuf, &buf, sizeof(struct compat_statfs64)))
return -EFAULT;
return 0;
}
int kcompat_sys_statfs64(const char __user * pathname, compat_size_t sz, struct compat_statfs64 __user * buf)
{
struct kstatfs tmp;
int error;
if (sz != sizeof(*buf))
return -EINVAL;
error = user_statfs(pathname, &tmp);
if (!error)
error = put_compat_statfs64(buf, &tmp);
return error;
}
COMPAT_SYSCALL_DEFINE3(statfs64, const char __user *, pathname, compat_size_t, sz, struct compat_statfs64 __user *, buf)
{
return kcompat_sys_statfs64(pathname, sz, buf);
}
int kcompat_sys_fstatfs64(unsigned int fd, compat_size_t sz, struct compat_statfs64 __user * buf)
{
struct kstatfs tmp;
int error;
if (sz != sizeof(*buf))
return -EINVAL;
error = fd_statfs(fd, &tmp);
if (!error)
error = put_compat_statfs64(buf, &tmp);
return error;
}
COMPAT_SYSCALL_DEFINE3(fstatfs64, unsigned int, fd, compat_size_t, sz, struct compat_statfs64 __user *, buf)
{
return kcompat_sys_fstatfs64(fd, sz, buf);
}
/*
* This is a copy of sys_ustat, just dealing with a structure layout.
* Given how simple this syscall is that apporach is more maintainable
* than the various conversion hacks.
*/
COMPAT_SYSCALL_DEFINE2(ustat, unsigned, dev, struct compat_ustat __user *, u)
{
struct compat_ustat tmp;
struct kstatfs sbuf;
int err = vfs_ustat(new_decode_dev(dev), &sbuf);
if (err)
return err;
memset(&tmp, 0, sizeof(struct compat_ustat));
tmp.f_tfree = sbuf.f_bfree;
tmp.f_tinode = sbuf.f_ffree;
if (copy_to_user(u, &tmp, sizeof(struct compat_ustat)))
return -EFAULT;
return 0;
}
#endif
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