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26e81b3)
The selection of a dentry for expiration and the setting of the
AUTOFS_INF_EXPIRING flag isn't done atomically which can lead to lookups
walking into an expiring mount.
What happens is that an expire is initiated by the daemon and a dentry is
selected for expire but, since there is no lock held between the selection
and setting of the expiring flag, a process may find the flag clear and
continue walking into the mount tree at the same time the daemon attempts
the expire it.
Signed-off-by: Ian Kent <raven@themaw.net>
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
static inline int autofs4_ispending(struct dentry *dentry)
{
struct autofs_info *inf = autofs4_dentry_ino(dentry);
static inline int autofs4_ispending(struct dentry *dentry)
{
struct autofs_info *inf = autofs4_dentry_ino(dentry);
if (dentry->d_flags & DCACHE_AUTOFS_PENDING)
return 1;
if (dentry->d_flags & DCACHE_AUTOFS_PENDING)
return 1;
- if (inf) {
- spin_lock(&inf->sbi->fs_lock);
- pending = inf->flags & AUTOFS_INF_EXPIRING;
- spin_unlock(&inf->sbi->fs_lock);
- }
+ if (inf->flags & AUTOFS_INF_EXPIRING)
+ return 1;
}
static inline void autofs4_copy_atime(struct file *src, struct file *dst)
}
static inline void autofs4_copy_atime(struct file *src, struct file *dst)
struct list_head *next;
int do_now = how & AUTOFS_EXP_IMMEDIATE;
int exp_leaves = how & AUTOFS_EXP_LEAVES;
struct list_head *next;
int do_now = how & AUTOFS_EXP_IMMEDIATE;
int exp_leaves = how & AUTOFS_EXP_LEAVES;
+ struct autofs_info *ino;
+ unsigned int ino_count;
dentry = dget(dentry);
spin_unlock(&dcache_lock);
dentry = dget(dentry);
spin_unlock(&dcache_lock);
+ spin_lock(&sbi->fs_lock);
+ ino = autofs4_dentry_ino(dentry);
+
/*
* Case 1: (i) indirect mount or top level pseudo direct mount
* (autofs-4.1).
/*
* Case 1: (i) indirect mount or top level pseudo direct mount
* (autofs-4.1).
DPRINTK("checking mountpoint %p %.*s",
dentry, (int)dentry->d_name.len, dentry->d_name.name);
DPRINTK("checking mountpoint %p %.*s",
dentry, (int)dentry->d_name.len, dentry->d_name.name);
+ /* Path walk currently on this dentry? */
+ ino_count = atomic_read(&ino->count) + 2;
+ if (atomic_read(&dentry->d_count) > ino_count)
+ goto next;
+
/* Can we umount this guy */
if (autofs4_mount_busy(mnt, dentry))
goto next;
/* Can we umount this guy */
if (autofs4_mount_busy(mnt, dentry))
goto next;
/* Case 2: tree mount, expire iff entire tree is not busy */
if (!exp_leaves) {
/* Case 2: tree mount, expire iff entire tree is not busy */
if (!exp_leaves) {
- /* Lock the tree as we must expire as a whole */
- spin_lock(&sbi->fs_lock);
- if (!autofs4_tree_busy(mnt, dentry, timeout, do_now)) {
- struct autofs_info *inf = autofs4_dentry_ino(dentry);
+ /* Path walk currently on this dentry? */
+ ino_count = atomic_read(&ino->count) + 1;
+ if (atomic_read(&dentry->d_count) > ino_count)
+ goto next;
- /* Set this flag early to catch sys_chdir and the like */
- inf->flags |= AUTOFS_INF_EXPIRING;
- spin_unlock(&sbi->fs_lock);
+ if (!autofs4_tree_busy(mnt, dentry, timeout, do_now)) {
expired = dentry;
goto found;
}
expired = dentry;
goto found;
}
- spin_unlock(&sbi->fs_lock);
/*
* Case 3: pseudo direct mount, expire individual leaves
* (autofs-4.1).
*/
} else {
/*
* Case 3: pseudo direct mount, expire individual leaves
* (autofs-4.1).
*/
} else {
+ /* Path walk currently on this dentry? */
+ ino_count = atomic_read(&ino->count) + 1;
+ if (atomic_read(&dentry->d_count) > ino_count)
+ goto next;
+
expired = autofs4_check_leaves(mnt, dentry, timeout, do_now);
if (expired) {
dput(dentry);
expired = autofs4_check_leaves(mnt, dentry, timeout, do_now);
if (expired) {
dput(dentry);
+ spin_unlock(&sbi->fs_lock);
dput(dentry);
spin_lock(&dcache_lock);
next = next->next;
dput(dentry);
spin_lock(&dcache_lock);
next = next->next;
found:
DPRINTK("returning %p %.*s",
expired, (int)expired->d_name.len, expired->d_name.name);
found:
DPRINTK("returning %p %.*s",
expired, (int)expired->d_name.len, expired->d_name.name);
+ ino = autofs4_dentry_ino(expired);
+ ino->flags |= AUTOFS_INF_EXPIRING;
+ spin_unlock(&sbi->fs_lock);
spin_lock(&dcache_lock);
list_move(&expired->d_parent->d_subdirs, &expired->d_u.d_child);
spin_unlock(&dcache_lock);
spin_lock(&dcache_lock);
list_move(&expired->d_parent->d_subdirs, &expired->d_u.d_child);
spin_unlock(&dcache_lock);
struct autofs_packet_expire __user *pkt_p)
{
struct autofs_packet_expire pkt;
struct autofs_packet_expire __user *pkt_p)
{
struct autofs_packet_expire pkt;
+ struct autofs_info *ino;
memset(&pkt,0,sizeof pkt);
memset(&pkt,0,sizeof pkt);
dput(dentry);
if ( copy_to_user(pkt_p, &pkt, sizeof(struct autofs_packet_expire)) )
dput(dentry);
if ( copy_to_user(pkt_p, &pkt, sizeof(struct autofs_packet_expire)) )
+ spin_lock(&sbi->fs_lock);
+ ino = autofs4_dentry_ino(dentry);
+ ino->flags &= ~AUTOFS_INF_EXPIRING;
+ spin_unlock(&sbi->fs_lock);
+
+ return ret;
}
/* Call repeatedly until it returns -EAGAIN, meaning there's nothing
}
/* Call repeatedly until it returns -EAGAIN, meaning there's nothing
/* This is synchronous because it makes the daemon a
little easier */
/* This is synchronous because it makes the daemon a
little easier */
- ino->flags |= AUTOFS_INF_EXPIRING;
ret = autofs4_wait(sbi, dentry, NFY_EXPIRE);
ret = autofs4_wait(sbi, dentry, NFY_EXPIRE);
+ spin_lock(&sbi->fs_lock);
ino->flags &= ~AUTOFS_INF_EXPIRING;
ino->flags &= ~AUTOFS_INF_EXPIRING;
+ spin_unlock(&sbi->fs_lock);
/* Block on any pending expiry here; invalidate the dentry
when expiration is done to trigger mount request with a new
dentry */
/* Block on any pending expiry here; invalidate the dentry
when expiration is done to trigger mount request with a new
dentry */
- if (ino && (ino->flags & AUTOFS_INF_EXPIRING)) {
+ spin_lock(&sbi->fs_lock);
+ if (ino->flags & AUTOFS_INF_EXPIRING) {
+ spin_unlock(&sbi->fs_lock);
+
DPRINTK("waiting for expire %p name=%.*s",
dentry, dentry->d_name.len, dentry->d_name.name);
DPRINTK("waiting for expire %p name=%.*s",
dentry, dentry->d_name.len, dentry->d_name.name);
status = d_invalidate(dentry);
if (status != -EBUSY)
return -EAGAIN;
status = d_invalidate(dentry);
if (status != -EBUSY)
return -EAGAIN;
+ goto cont;
+ }
+ spin_unlock(&sbi->fs_lock);
+cont:
DPRINTK("dentry=%p %.*s ino=%p",
dentry, dentry->d_name.len, dentry->d_name.name, dentry->d_inode);
DPRINTK("dentry=%p %.*s ino=%p",
dentry, dentry->d_name.len, dentry->d_name.name, dentry->d_inode);
goto done;
/* If an expire request is pending wait for it. */
goto done;
/* If an expire request is pending wait for it. */
- if (ino && (ino->flags & AUTOFS_INF_EXPIRING)) {
+ spin_lock(&sbi->fs_lock);
+ if (ino->flags & AUTOFS_INF_EXPIRING) {
+ spin_unlock(&sbi->fs_lock);
+
DPRINTK("waiting for active request %p name=%.*s",
dentry, dentry->d_name.len, dentry->d_name.name);
status = autofs4_wait(sbi, dentry, NFY_NONE);
DPRINTK("request done status=%d", status);
DPRINTK("waiting for active request %p name=%.*s",
dentry, dentry->d_name.len, dentry->d_name.name);
status = autofs4_wait(sbi, dentry, NFY_NONE);
DPRINTK("request done status=%d", status);
+ goto cont;
+ }
+ spin_unlock(&sbi->fs_lock);
+cont:
/*
* If the dentry contains directories then it is an
* autofs multi-mount with no root mount offset. So
/*
* If the dentry contains directories then it is an
* autofs multi-mount with no root mount offset. So
int status = 1;
/* Pending dentry */
int status = 1;
/* Pending dentry */
+ spin_lock(&sbi->fs_lock);
if (autofs4_ispending(dentry)) {
/* The daemon never causes a mount to trigger */
if (autofs4_ispending(dentry)) {
/* The daemon never causes a mount to trigger */
+ spin_unlock(&sbi->fs_lock);
+
+ spin_unlock(&sbi->fs_lock);
/* Negative dentry.. invalidate if "old" */
if (dentry->d_inode == NULL)
/* Negative dentry.. invalidate if "old" */
if (dentry->d_inode == NULL)
DPRINTK("dentry=%p %.*s, emptydir",
dentry, dentry->d_name.len, dentry->d_name.name);
spin_unlock(&dcache_lock);
DPRINTK("dentry=%p %.*s, emptydir",
dentry, dentry->d_name.len, dentry->d_name.name);
spin_unlock(&dcache_lock);
/* The daemon never causes a mount to trigger */
if (oz_mode)
return 1;
/* The daemon never causes a mount to trigger */
if (oz_mode)
return 1;
* so it must have been successful, so just wait for it.
*/
ino = autofs4_dentry_ino(expiring);
* so it must have been successful, so just wait for it.
*/
ino = autofs4_dentry_ino(expiring);
- while (ino && (ino->flags & AUTOFS_INF_EXPIRING)) {
+ spin_lock(&sbi->fs_lock);
+ if (ino->flags & AUTOFS_INF_EXPIRING) {
+ spin_unlock(&sbi->fs_lock);
DPRINTK("wait for incomplete expire %p name=%.*s",
expiring, expiring->d_name.len,
expiring->d_name.name);
autofs4_wait(sbi, expiring, NFY_NONE);
DPRINTK("request completed");
DPRINTK("wait for incomplete expire %p name=%.*s",
expiring, expiring->d_name.len,
expiring->d_name.name);
autofs4_wait(sbi, expiring, NFY_NONE);
DPRINTK("request completed");
+ spin_unlock(&sbi->fs_lock);
+cont:
spin_lock(&sbi->lookup_lock);
if (!list_empty(&ino->expiring))
list_del_init(&ino->expiring);
spin_lock(&sbi->lookup_lock);
if (!list_empty(&ino->expiring))
list_del_init(&ino->expiring);