compat_ioctl: don't call do_ioctl under set_fs(KERNEL_DS)
This replaces all code in fs/compat_ioctl.c that translated
ioctl arguments into a in-kernel structure, then performed
do_ioctl under set_fs(KERNEL_DS), with code that allocates
data on the user stack and can call the VFS ioctl handler
under USER_DS.
This is done as a hardening measure because the caller
does not know what kind of ioctl handler will be invoked,
only that no corresponding compat_ioctl handler exists and
what the ioctl command number is. The accidental
invocation of an unlocked_ioctl handler that unexpectedly
calls copy_to_user could be a severe security issue.
Signed-off-by: Jann Horn <jann@thejh.net>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/compat_ioctl.c b/fs/compat_ioctl.c
index 908837c..9144b77 100644
--- a/fs/compat_ioctl.c
+++ b/fs/compat_ioctl.c
@@ -117,6 +117,13 @@
#include <asm/fbio.h>
#endif
+#define convert_in_user(srcptr, dstptr) \
+({ \
+ typeof(*srcptr) val; \
+ \
+ get_user(val, srcptr) || put_user(val, dstptr); \
+})
+
static int do_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
int err;
@@ -131,16 +138,17 @@
static int w_long(struct file *file,
unsigned int cmd, compat_ulong_t __user *argp)
{
- mm_segment_t old_fs = get_fs();
int err;
- unsigned long val;
+ unsigned long __user *valp = compat_alloc_user_space(sizeof(*valp));
- set_fs (KERNEL_DS);
- err = do_ioctl(file, cmd, (unsigned long)&val);
- set_fs (old_fs);
- if (!err && put_user(val, argp))
+ if (valp == NULL)
return -EFAULT;
- return err;
+ err = do_ioctl(file, cmd, (unsigned long)valp);
+ if (err)
+ return err;
+ if (convert_in_user(valp, argp))
+ return -EFAULT;
+ return 0;
}
struct compat_video_event {
@@ -155,20 +163,20 @@
static int do_video_get_event(struct file *file,
unsigned int cmd, struct compat_video_event __user *up)
{
- struct video_event kevent;
- mm_segment_t old_fs = get_fs();
+ struct video_event __user *kevent =
+ compat_alloc_user_space(sizeof(*kevent));
int err;
- set_fs(KERNEL_DS);
- err = do_ioctl(file, cmd, (unsigned long) &kevent);
- set_fs(old_fs);
+ if (kevent == NULL)
+ return -EFAULT;
+ err = do_ioctl(file, cmd, (unsigned long)kevent);
if (!err) {
- err = put_user(kevent.type, &up->type);
- err |= put_user(kevent.timestamp, &up->timestamp);
- err |= put_user(kevent.u.size.w, &up->u.size.w);
- err |= put_user(kevent.u.size.h, &up->u.size.h);
- err |= put_user(kevent.u.size.aspect_ratio,
+ err = convert_in_user(&kevent->type, &up->type);
+ err |= convert_in_user(&kevent->timestamp, &up->timestamp);
+ err |= convert_in_user(&kevent->u.size.w, &up->u.size.w);
+ err |= convert_in_user(&kevent->u.size.h, &up->u.size.h);
+ err |= convert_in_user(&kevent->u.size.aspect_ratio,
&up->u.size.aspect_ratio);
if (err)
err = -EFAULT;
@@ -528,10 +536,10 @@
static int mt_ioctl_trans(struct file *file,
unsigned int cmd, void __user *argp)
{
- mm_segment_t old_fs = get_fs();
- struct mtget get;
+ /* NULL initialization to make gcc shut up */
+ struct mtget __user *get = NULL;
struct mtget32 __user *umget32;
- struct mtpos pos;
+ struct mtpos __user *pos = NULL;
struct mtpos32 __user *upos32;
unsigned long kcmd;
void *karg;
@@ -540,32 +548,34 @@
switch(cmd) {
case MTIOCPOS32:
kcmd = MTIOCPOS;
- karg = &pos;
+ pos = compat_alloc_user_space(sizeof(*pos));
+ karg = pos;
break;
default: /* MTIOCGET32 */
kcmd = MTIOCGET;
- karg = &get;
+ get = compat_alloc_user_space(sizeof(*get));
+ karg = get;
break;
}
- set_fs (KERNEL_DS);
+ if (karg == NULL)
+ return -EFAULT;
err = do_ioctl(file, kcmd, (unsigned long)karg);
- set_fs (old_fs);
if (err)
return err;
switch (cmd) {
case MTIOCPOS32:
upos32 = argp;
- err = __put_user(pos.mt_blkno, &upos32->mt_blkno);
+ err = convert_in_user(&pos->mt_blkno, &upos32->mt_blkno);
break;
case MTIOCGET32:
umget32 = argp;
- err = __put_user(get.mt_type, &umget32->mt_type);
- err |= __put_user(get.mt_resid, &umget32->mt_resid);
- err |= __put_user(get.mt_dsreg, &umget32->mt_dsreg);
- err |= __put_user(get.mt_gstat, &umget32->mt_gstat);
- err |= __put_user(get.mt_erreg, &umget32->mt_erreg);
- err |= __put_user(get.mt_fileno, &umget32->mt_fileno);
- err |= __put_user(get.mt_blkno, &umget32->mt_blkno);
+ err = convert_in_user(&get->mt_type, &umget32->mt_type);
+ err |= convert_in_user(&get->mt_resid, &umget32->mt_resid);
+ err |= convert_in_user(&get->mt_dsreg, &umget32->mt_dsreg);
+ err |= convert_in_user(&get->mt_gstat, &umget32->mt_gstat);
+ err |= convert_in_user(&get->mt_erreg, &umget32->mt_erreg);
+ err |= convert_in_user(&get->mt_fileno, &umget32->mt_fileno);
+ err |= convert_in_user(&get->mt_blkno, &umget32->mt_blkno);
break;
}
return err ? -EFAULT: 0;
@@ -624,37 +634,36 @@
{
typedef struct serial_struct32 SS32;
int err;
- struct serial_struct ss;
- mm_segment_t oldseg = get_fs();
+ struct serial_struct __user *ss = compat_alloc_user_space(sizeof(*ss));
__u32 udata;
unsigned int base;
+ unsigned char *iomem_base;
+ if (ss == NULL)
+ return -EFAULT;
if (cmd == TIOCSSERIAL) {
- if (!access_ok(VERIFY_READ, ss32, sizeof(SS32)))
- return -EFAULT;
- if (__copy_from_user(&ss, ss32, offsetof(SS32, iomem_base)))
+ if (copy_in_user(ss, ss32, offsetof(SS32, iomem_base)) ||
+ get_user(udata, &ss32->iomem_base))
return -EFAULT;
- if (__get_user(udata, &ss32->iomem_base))
+ iomem_base = compat_ptr(udata);
+ if (put_user(iomem_base, &ss->iomem_base) ||
+ convert_in_user(&ss32->iomem_reg_shift,
+ &ss->iomem_reg_shift) ||
+ convert_in_user(&ss32->port_high, &ss->port_high) ||
+ put_user(0UL, &ss->iomap_base))
return -EFAULT;
- ss.iomem_base = compat_ptr(udata);
- if (__get_user(ss.iomem_reg_shift, &ss32->iomem_reg_shift) ||
- __get_user(ss.port_high, &ss32->port_high))
- return -EFAULT;
- ss.iomap_base = 0UL;
}
- set_fs(KERNEL_DS);
- err = do_ioctl(file, cmd, (unsigned long)&ss);
- set_fs(oldseg);
+ err = do_ioctl(file, cmd, (unsigned long)ss);
if (cmd == TIOCGSERIAL && err >= 0) {
- if (!access_ok(VERIFY_WRITE, ss32, sizeof(SS32)))
- return -EFAULT;
- if (__copy_to_user(ss32,&ss,offsetof(SS32,iomem_base)))
+ if (copy_in_user(ss32, ss, offsetof(SS32, iomem_base)) ||
+ get_user(iomem_base, &ss->iomem_base))
return -EFAULT;
- base = (unsigned long)ss.iomem_base >> 32 ?
- 0xffffffff : (unsigned)(unsigned long)ss.iomem_base;
- if (__put_user(base, &ss32->iomem_base) ||
- __put_user(ss.iomem_reg_shift, &ss32->iomem_reg_shift) ||
- __put_user(ss.port_high, &ss32->port_high))
+ base = (unsigned long)iomem_base >> 32 ?
+ 0xffffffff : (unsigned)(unsigned long)iomem_base;
+ if (put_user(base, &ss32->iomem_base) ||
+ convert_in_user(&ss->iomem_reg_shift,
+ &ss32->iomem_reg_shift) ||
+ convert_in_user(&ss->port_high, &ss32->port_high))
return -EFAULT;
}
return err;
@@ -759,23 +768,20 @@
static int rtc_ioctl(struct file *file,
unsigned cmd, void __user *argp)
{
- mm_segment_t oldfs = get_fs();
- compat_ulong_t val32;
- unsigned long kval;
+ unsigned long __user *valp = compat_alloc_user_space(sizeof(*valp));
int ret;
+ if (valp == NULL)
+ return -EFAULT;
switch (cmd) {
case RTC_IRQP_READ32:
case RTC_EPOCH_READ32:
- set_fs(KERNEL_DS);
ret = do_ioctl(file, (cmd == RTC_IRQP_READ32) ?
RTC_IRQP_READ : RTC_EPOCH_READ,
- (unsigned long)&kval);
- set_fs(oldfs);
+ (unsigned long)valp);
if (ret)
return ret;
- val32 = kval;
- return put_user(val32, (unsigned int __user *)argp);
+ return convert_in_user(valp, (unsigned int __user *)argp);
case RTC_IRQP_SET32:
return do_ioctl(file, RTC_IRQP_SET, (unsigned long)argp);
case RTC_EPOCH_SET32: