Revision 4a53d3afa00b0b74b0e49b147902a41e55b2e715 authored by Lars-Peter Clausen on 25 September 2014, 14:27:00 UTC, committed by Jonathan Cameron on 05 November 2014, 18:33:41 UTC
In older versions of the IIO framework it was possible to pass a completely different set of channels to iio_buffer_register() as the one that is assigned to the IIO device. Commit 959d2952d124 ("staging:iio: make iio_sw_buffer_preenable much more general.") introduced a restriction that requires that the set of channels that is passed to iio_buffer_register() is a subset of the channels assigned to the IIO device as the IIO core will use the list of channels that is assigned to the device to lookup a channel by scan index in iio_compute_scan_bytes(). If it can not find the channel the function will crash. This patch fixes the issue by making sure that the same set of channels is assigned to the IIO device and passed to iio_buffer_register(). Fixes the follow NULL pointer derefernce kernel crash: Unable to handle kernel NULL pointer dereference at virtual address 00000016 pgd = d53d0000 [00000016] *pgd=1534e831, *pte=00000000, *ppte=00000000 Internal error: Oops: 17 [#1] PREEMPT SMP ARM Modules linked in: CPU: 1 PID: 1626 Comm: bash Not tainted 3.15.0-19969-g2a180eb-dirty #9545 task: d6c124c0 ti: d539a000 task.ti: d539a000 PC is at iio_compute_scan_bytes+0x34/0xa8 LR is at iio_compute_scan_bytes+0x34/0xa8 pc : [<c03052e4>] lr : [<c03052e4>] psr: 60070013 sp : d539beb8 ip : 00000001 fp : 00000000 r10: 00000002 r9 : 00000000 r8 : 00000001 r7 : 00000000 r6 : d6dc8800 r5 : d7571000 r4 : 00000002 r3 : d7571000 r2 : 00000044 r1 : 00000001 r0 : 00000000 Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user Control: 18c5387d Table: 153d004a DAC: 00000015 Process bash (pid: 1626, stack limit = 0xd539a240) Stack: (0xd539beb8 to 0xd539c000) bea0: c02fc0e4 d7571000 bec0: d76c1640 d6dc8800 d757117c 00000000 d757112c c0305b04 d76c1690 d76c1640 bee0: d7571188 00000002 00000000 d7571000 d539a000 00000000 000dd1c8 c0305d54 bf00: d7571010 0160b868 00000002 c69d3900 d7573278 d7573308 c69d3900 c01ece90 bf20: 00000002 c0103fac c0103f6c d539bf88 00000002 c69d3b00 c69d3b0c c0103468 bf40: 00000000 00000000 d7694a00 00000002 000af408 d539bf88 c000dd84 c00b2f94 bf60: d7694a00 000af408 00000002 d7694a00 d7694a00 00000002 000af408 c000dd84 bf80: 00000000 c00b32d0 00000000 00000000 00000002 b6f1aa78 00000002 000af408 bfa0: 00000004 c000dc00 b6f1aa78 00000002 00000001 000af408 00000002 00000000 bfc0: b6f1aa78 00000002 000af408 00000004 be806a4c 000a6094 00000000 000dd1c8 bfe0: 00000000 be8069cc b6e8ab77 b6ec125c 40070010 00000001 22940489 154a5007 [<c03052e4>] (iio_compute_scan_bytes) from [<c0305b04>] (__iio_update_buffers+0x248/0x438) [<c0305b04>] (__iio_update_buffers) from [<c0305d54>] (iio_buffer_store_enable+0x60/0x7c) [<c0305d54>] (iio_buffer_store_enable) from [<c01ece90>] (dev_attr_store+0x18/0x24) [<c01ece90>] (dev_attr_store) from [<c0103fac>] (sysfs_kf_write+0x40/0x4c) [<c0103fac>] (sysfs_kf_write) from [<c0103468>] (kernfs_fop_write+0x110/0x154) [<c0103468>] (kernfs_fop_write) from [<c00b2f94>] (vfs_write+0xd0/0x160) [<c00b2f94>] (vfs_write) from [<c00b32d0>] (SyS_write+0x40/0x78) [<c00b32d0>] (SyS_write) from [<c000dc00>] (ret_fast_syscall+0x0/0x30) Code: ea00000e e1a01008 e1a00005 ebfff6fc (e5d0a016) Fixes: 959d2952d124 ("staging:iio: make iio_sw_buffer_preenable much more general.") Signed-off-by: Lars-Peter Clausen <lars@metafoo.de> Cc: Stable@vger.kernel.org Signed-off-by: Jonathan Cameron <jic23@kernel.org>
1 parent 54d5c5c
pnode.c
/*
* linux/fs/pnode.c
*
* (C) Copyright IBM Corporation 2005.
* Released under GPL v2.
* Author : Ram Pai (linuxram@us.ibm.com)
*
*/
#include <linux/mnt_namespace.h>
#include <linux/mount.h>
#include <linux/fs.h>
#include <linux/nsproxy.h>
#include "internal.h"
#include "pnode.h"
/* return the next shared peer mount of @p */
static inline struct mount *next_peer(struct mount *p)
{
return list_entry(p->mnt_share.next, struct mount, mnt_share);
}
static inline struct mount *first_slave(struct mount *p)
{
return list_entry(p->mnt_slave_list.next, struct mount, mnt_slave);
}
static inline struct mount *next_slave(struct mount *p)
{
return list_entry(p->mnt_slave.next, struct mount, mnt_slave);
}
static struct mount *get_peer_under_root(struct mount *mnt,
struct mnt_namespace *ns,
const struct path *root)
{
struct mount *m = mnt;
do {
/* Check the namespace first for optimization */
if (m->mnt_ns == ns && is_path_reachable(m, m->mnt.mnt_root, root))
return m;
m = next_peer(m);
} while (m != mnt);
return NULL;
}
/*
* Get ID of closest dominating peer group having a representative
* under the given root.
*
* Caller must hold namespace_sem
*/
int get_dominating_id(struct mount *mnt, const struct path *root)
{
struct mount *m;
for (m = mnt->mnt_master; m != NULL; m = m->mnt_master) {
struct mount *d = get_peer_under_root(m, mnt->mnt_ns, root);
if (d)
return d->mnt_group_id;
}
return 0;
}
static int do_make_slave(struct mount *mnt)
{
struct mount *peer_mnt = mnt, *master = mnt->mnt_master;
struct mount *slave_mnt;
/*
* slave 'mnt' to a peer mount that has the
* same root dentry. If none is available then
* slave it to anything that is available.
*/
while ((peer_mnt = next_peer(peer_mnt)) != mnt &&
peer_mnt->mnt.mnt_root != mnt->mnt.mnt_root) ;
if (peer_mnt == mnt) {
peer_mnt = next_peer(mnt);
if (peer_mnt == mnt)
peer_mnt = NULL;
}
if (mnt->mnt_group_id && IS_MNT_SHARED(mnt) &&
list_empty(&mnt->mnt_share))
mnt_release_group_id(mnt);
list_del_init(&mnt->mnt_share);
mnt->mnt_group_id = 0;
if (peer_mnt)
master = peer_mnt;
if (master) {
list_for_each_entry(slave_mnt, &mnt->mnt_slave_list, mnt_slave)
slave_mnt->mnt_master = master;
list_move(&mnt->mnt_slave, &master->mnt_slave_list);
list_splice(&mnt->mnt_slave_list, master->mnt_slave_list.prev);
INIT_LIST_HEAD(&mnt->mnt_slave_list);
} else {
struct list_head *p = &mnt->mnt_slave_list;
while (!list_empty(p)) {
slave_mnt = list_first_entry(p,
struct mount, mnt_slave);
list_del_init(&slave_mnt->mnt_slave);
slave_mnt->mnt_master = NULL;
}
}
mnt->mnt_master = master;
CLEAR_MNT_SHARED(mnt);
return 0;
}
/*
* vfsmount lock must be held for write
*/
void change_mnt_propagation(struct mount *mnt, int type)
{
if (type == MS_SHARED) {
set_mnt_shared(mnt);
return;
}
do_make_slave(mnt);
if (type != MS_SLAVE) {
list_del_init(&mnt->mnt_slave);
mnt->mnt_master = NULL;
if (type == MS_UNBINDABLE)
mnt->mnt.mnt_flags |= MNT_UNBINDABLE;
else
mnt->mnt.mnt_flags &= ~MNT_UNBINDABLE;
}
}
/*
* get the next mount in the propagation tree.
* @m: the mount seen last
* @origin: the original mount from where the tree walk initiated
*
* Note that peer groups form contiguous segments of slave lists.
* We rely on that in get_source() to be able to find out if
* vfsmount found while iterating with propagation_next() is
* a peer of one we'd found earlier.
*/
static struct mount *propagation_next(struct mount *m,
struct mount *origin)
{
/* are there any slaves of this mount? */
if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list))
return first_slave(m);
while (1) {
struct mount *master = m->mnt_master;
if (master == origin->mnt_master) {
struct mount *next = next_peer(m);
return (next == origin) ? NULL : next;
} else if (m->mnt_slave.next != &master->mnt_slave_list)
return next_slave(m);
/* back at master */
m = master;
}
}
static struct mount *next_group(struct mount *m, struct mount *origin)
{
while (1) {
while (1) {
struct mount *next;
if (!IS_MNT_NEW(m) && !list_empty(&m->mnt_slave_list))
return first_slave(m);
next = next_peer(m);
if (m->mnt_group_id == origin->mnt_group_id) {
if (next == origin)
return NULL;
} else if (m->mnt_slave.next != &next->mnt_slave)
break;
m = next;
}
/* m is the last peer */
while (1) {
struct mount *master = m->mnt_master;
if (m->mnt_slave.next != &master->mnt_slave_list)
return next_slave(m);
m = next_peer(master);
if (master->mnt_group_id == origin->mnt_group_id)
break;
if (master->mnt_slave.next == &m->mnt_slave)
break;
m = master;
}
if (m == origin)
return NULL;
}
}
/* all accesses are serialized by namespace_sem */
static struct user_namespace *user_ns;
static struct mount *last_dest, *last_source, *dest_master;
static struct mountpoint *mp;
static struct hlist_head *list;
static int propagate_one(struct mount *m)
{
struct mount *child;
int type;
/* skip ones added by this propagate_mnt() */
if (IS_MNT_NEW(m))
return 0;
/* skip if mountpoint isn't covered by it */
if (!is_subdir(mp->m_dentry, m->mnt.mnt_root))
return 0;
if (m->mnt_group_id == last_dest->mnt_group_id) {
type = CL_MAKE_SHARED;
} else {
struct mount *n, *p;
for (n = m; ; n = p) {
p = n->mnt_master;
if (p == dest_master || IS_MNT_MARKED(p)) {
while (last_dest->mnt_master != p) {
last_source = last_source->mnt_master;
last_dest = last_source->mnt_parent;
}
if (n->mnt_group_id != last_dest->mnt_group_id) {
last_source = last_source->mnt_master;
last_dest = last_source->mnt_parent;
}
break;
}
}
type = CL_SLAVE;
/* beginning of peer group among the slaves? */
if (IS_MNT_SHARED(m))
type |= CL_MAKE_SHARED;
}
/* Notice when we are propagating across user namespaces */
if (m->mnt_ns->user_ns != user_ns)
type |= CL_UNPRIVILEGED;
child = copy_tree(last_source, last_source->mnt.mnt_root, type);
if (IS_ERR(child))
return PTR_ERR(child);
mnt_set_mountpoint(m, mp, child);
last_dest = m;
last_source = child;
if (m->mnt_master != dest_master) {
read_seqlock_excl(&mount_lock);
SET_MNT_MARK(m->mnt_master);
read_sequnlock_excl(&mount_lock);
}
hlist_add_head(&child->mnt_hash, list);
return 0;
}
/*
* mount 'source_mnt' under the destination 'dest_mnt' at
* dentry 'dest_dentry'. And propagate that mount to
* all the peer and slave mounts of 'dest_mnt'.
* Link all the new mounts into a propagation tree headed at
* source_mnt. Also link all the new mounts using ->mnt_list
* headed at source_mnt's ->mnt_list
*
* @dest_mnt: destination mount.
* @dest_dentry: destination dentry.
* @source_mnt: source mount.
* @tree_list : list of heads of trees to be attached.
*/
int propagate_mnt(struct mount *dest_mnt, struct mountpoint *dest_mp,
struct mount *source_mnt, struct hlist_head *tree_list)
{
struct mount *m, *n;
int ret = 0;
/*
* we don't want to bother passing tons of arguments to
* propagate_one(); everything is serialized by namespace_sem,
* so globals will do just fine.
*/
user_ns = current->nsproxy->mnt_ns->user_ns;
last_dest = dest_mnt;
last_source = source_mnt;
mp = dest_mp;
list = tree_list;
dest_master = dest_mnt->mnt_master;
/* all peers of dest_mnt, except dest_mnt itself */
for (n = next_peer(dest_mnt); n != dest_mnt; n = next_peer(n)) {
ret = propagate_one(n);
if (ret)
goto out;
}
/* all slave groups */
for (m = next_group(dest_mnt, dest_mnt); m;
m = next_group(m, dest_mnt)) {
/* everything in that slave group */
n = m;
do {
ret = propagate_one(n);
if (ret)
goto out;
n = next_peer(n);
} while (n != m);
}
out:
read_seqlock_excl(&mount_lock);
hlist_for_each_entry(n, tree_list, mnt_hash) {
m = n->mnt_parent;
if (m->mnt_master != dest_mnt->mnt_master)
CLEAR_MNT_MARK(m->mnt_master);
}
read_sequnlock_excl(&mount_lock);
return ret;
}
/*
* return true if the refcount is greater than count
*/
static inline int do_refcount_check(struct mount *mnt, int count)
{
return mnt_get_count(mnt) > count;
}
/*
* check if the mount 'mnt' can be unmounted successfully.
* @mnt: the mount to be checked for unmount
* NOTE: unmounting 'mnt' would naturally propagate to all
* other mounts its parent propagates to.
* Check if any of these mounts that **do not have submounts**
* have more references than 'refcnt'. If so return busy.
*
* vfsmount lock must be held for write
*/
int propagate_mount_busy(struct mount *mnt, int refcnt)
{
struct mount *m, *child;
struct mount *parent = mnt->mnt_parent;
int ret = 0;
if (mnt == parent)
return do_refcount_check(mnt, refcnt);
/*
* quickly check if the current mount can be unmounted.
* If not, we don't have to go checking for all other
* mounts
*/
if (!list_empty(&mnt->mnt_mounts) || do_refcount_check(mnt, refcnt))
return 1;
for (m = propagation_next(parent, parent); m;
m = propagation_next(m, parent)) {
child = __lookup_mnt_last(&m->mnt, mnt->mnt_mountpoint);
if (child && list_empty(&child->mnt_mounts) &&
(ret = do_refcount_check(child, 1)))
break;
}
return ret;
}
/*
* NOTE: unmounting 'mnt' naturally propagates to all other mounts its
* parent propagates to.
*/
static void __propagate_umount(struct mount *mnt)
{
struct mount *parent = mnt->mnt_parent;
struct mount *m;
BUG_ON(parent == mnt);
for (m = propagation_next(parent, parent); m;
m = propagation_next(m, parent)) {
struct mount *child = __lookup_mnt_last(&m->mnt,
mnt->mnt_mountpoint);
/*
* umount the child only if the child has no
* other children
*/
if (child && list_empty(&child->mnt_mounts)) {
list_del_init(&child->mnt_child);
hlist_del_init_rcu(&child->mnt_hash);
hlist_add_before_rcu(&child->mnt_hash, &mnt->mnt_hash);
}
}
}
/*
* collect all mounts that receive propagation from the mount in @list,
* and return these additional mounts in the same list.
* @list: the list of mounts to be unmounted.
*
* vfsmount lock must be held for write
*/
int propagate_umount(struct hlist_head *list)
{
struct mount *mnt;
hlist_for_each_entry(mnt, list, mnt_hash)
__propagate_umount(mnt);
return 0;
}
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