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-rw-r--r--fs/namei.c89
1 files changed, 44 insertions, 45 deletions
diff --git a/fs/namei.c b/fs/namei.c
index 78443a85480a..de74ad2bc6e2 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -630,6 +630,11 @@ static inline bool legitimize_path(struct nameidata *nd,
static bool legitimize_links(struct nameidata *nd)
{
int i;
+ if (unlikely(nd->flags & LOOKUP_CACHED)) {
+ drop_links(nd);
+ nd->depth = 0;
+ return false;
+ }
for (i = 0; i < nd->depth; i++) {
struct saved *last = nd->stack + i;
if (unlikely(!legitimize_path(nd, &last->link, last->seq))) {
@@ -669,17 +674,17 @@ static bool legitimize_root(struct nameidata *nd)
*/
/**
- * unlazy_walk - try to switch to ref-walk mode.
+ * try_to_unlazy - try to switch to ref-walk mode.
* @nd: nameidata pathwalk data
- * Returns: 0 on success, -ECHILD on failure
+ * Returns: true on success, false on failure
*
- * unlazy_walk attempts to legitimize the current nd->path and nd->root
+ * try_to_unlazy attempts to legitimize the current nd->path and nd->root
* for ref-walk mode.
* Must be called from rcu-walk context.
- * Nothing should touch nameidata between unlazy_walk() failure and
+ * Nothing should touch nameidata between try_to_unlazy() failure and
* terminate_walk().
*/
-static int unlazy_walk(struct nameidata *nd)
+static bool try_to_unlazy(struct nameidata *nd)
{
struct dentry *parent = nd->path.dentry;
@@ -694,30 +699,30 @@ static int unlazy_walk(struct nameidata *nd)
goto out;
rcu_read_unlock();
BUG_ON(nd->inode != parent->d_inode);
- return 0;
+ return true;
out1:
nd->path.mnt = NULL;
nd->path.dentry = NULL;
out:
rcu_read_unlock();
- return -ECHILD;
+ return false;
}
/**
- * unlazy_child - try to switch to ref-walk mode.
+ * try_to_unlazy_next - try to switch to ref-walk mode.
* @nd: nameidata pathwalk data
- * @dentry: child of nd->path.dentry
- * @seq: seq number to check dentry against
- * Returns: 0 on success, -ECHILD on failure
+ * @dentry: next dentry to step into
+ * @seq: seq number to check @dentry against
+ * Returns: true on success, false on failure
*
- * unlazy_child attempts to legitimize the current nd->path, nd->root and dentry
- * for ref-walk mode. @dentry must be a path found by a do_lookup call on
- * @nd. Must be called from rcu-walk context.
- * Nothing should touch nameidata between unlazy_child() failure and
+ * Similar to to try_to_unlazy(), but here we have the next dentry already
+ * picked by rcu-walk and want to legitimize that in addition to the current
+ * nd->path and nd->root for ref-walk mode. Must be called from rcu-walk context.
+ * Nothing should touch nameidata between try_to_unlazy_next() failure and
* terminate_walk().
*/
-static int unlazy_child(struct nameidata *nd, struct dentry *dentry, unsigned seq)
+static bool try_to_unlazy_next(struct nameidata *nd, struct dentry *dentry, unsigned seq)
{
BUG_ON(!(nd->flags & LOOKUP_RCU));
@@ -747,7 +752,7 @@ static int unlazy_child(struct nameidata *nd, struct dentry *dentry, unsigned se
if (unlikely(!legitimize_root(nd)))
goto out_dput;
rcu_read_unlock();
- return 0;
+ return true;
out2:
nd->path.mnt = NULL;
@@ -755,11 +760,11 @@ out1:
nd->path.dentry = NULL;
out:
rcu_read_unlock();
- return -ECHILD;
+ return false;
out_dput:
rcu_read_unlock();
dput(dentry);
- return -ECHILD;
+ return false;
}
static inline int d_revalidate(struct dentry *dentry, unsigned int flags)
@@ -792,7 +797,8 @@ static int complete_walk(struct nameidata *nd)
*/
if (!(nd->flags & (LOOKUP_ROOT | LOOKUP_IS_SCOPED)))
nd->root.mnt = NULL;
- if (unlikely(unlazy_walk(nd)))
+ nd->flags &= ~LOOKUP_CACHED;
+ if (!try_to_unlazy(nd))
return -ECHILD;
}
@@ -1372,7 +1378,7 @@ static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry,
return -ENOENT;
if (likely(__follow_mount_rcu(nd, path, inode, seqp)))
return 0;
- if (unlazy_child(nd, dentry, seq))
+ if (!try_to_unlazy_next(nd, dentry, seq))
return -ECHILD;
// *path might've been clobbered by __follow_mount_rcu()
path->mnt = nd->path.mnt;
@@ -1466,7 +1472,7 @@ static struct dentry *lookup_fast(struct nameidata *nd,
unsigned seq;
dentry = __d_lookup_rcu(parent, &nd->last, &seq);
if (unlikely(!dentry)) {
- if (unlazy_walk(nd))
+ if (!try_to_unlazy(nd))
return ERR_PTR(-ECHILD);
return NULL;
}
@@ -1493,9 +1499,9 @@ static struct dentry *lookup_fast(struct nameidata *nd,
status = d_revalidate(dentry, nd->flags);
if (likely(status > 0))
return dentry;
- if (unlazy_child(nd, dentry, seq))
+ if (!try_to_unlazy_next(nd, dentry, seq))
return ERR_PTR(-ECHILD);
- if (unlikely(status == -ECHILD))
+ if (status == -ECHILD)
/* we'd been told to redo it in non-rcu mode */
status = d_revalidate(dentry, nd->flags);
} else {
@@ -1567,10 +1573,8 @@ static inline int may_lookup(struct nameidata *nd)
{
if (nd->flags & LOOKUP_RCU) {
int err = inode_permission(nd->inode, MAY_EXEC|MAY_NOT_BLOCK);
- if (err != -ECHILD)
+ if (err != -ECHILD || !try_to_unlazy(nd))
return err;
- if (unlazy_walk(nd))
- return -ECHILD;
}
return inode_permission(nd->inode, MAY_EXEC);
}
@@ -1592,7 +1596,7 @@ static int reserve_stack(struct nameidata *nd, struct path *link, unsigned seq)
// unlazy even if we fail to grab the link - cleanup needs it
bool grabbed_link = legitimize_path(nd, link, seq);
- if (unlazy_walk(nd) != 0 || !grabbed_link)
+ if (!try_to_unlazy(nd) != 0 || !grabbed_link)
return -ECHILD;
if (nd_alloc_stack(nd))
@@ -1634,7 +1638,7 @@ static const char *pick_link(struct nameidata *nd, struct path *link,
touch_atime(&last->link);
cond_resched();
} else if (atime_needs_update(&last->link, inode)) {
- if (unlikely(unlazy_walk(nd)))
+ if (!try_to_unlazy(nd))
return ERR_PTR(-ECHILD);
touch_atime(&last->link);
}
@@ -1651,11 +1655,8 @@ static const char *pick_link(struct nameidata *nd, struct path *link,
get = inode->i_op->get_link;
if (nd->flags & LOOKUP_RCU) {
res = get(NULL, inode, &last->done);
- if (res == ERR_PTR(-ECHILD)) {
- if (unlikely(unlazy_walk(nd)))
- return ERR_PTR(-ECHILD);
+ if (res == ERR_PTR(-ECHILD) && try_to_unlazy(nd))
res = get(link->dentry, inode, &last->done);
- }
} else {
res = get(link->dentry, inode, &last->done);
}
@@ -2195,7 +2196,7 @@ OK:
}
if (unlikely(!d_can_lookup(nd->path.dentry))) {
if (nd->flags & LOOKUP_RCU) {
- if (unlazy_walk(nd))
+ if (!try_to_unlazy(nd))
return -ECHILD;
}
return -ENOTDIR;
@@ -2209,6 +2210,10 @@ static const char *path_init(struct nameidata *nd, unsigned flags)
int error;
const char *s = nd->name->name;
+ /* LOOKUP_CACHED requires RCU, ask caller to retry */
+ if ((flags & (LOOKUP_RCU | LOOKUP_CACHED)) == LOOKUP_CACHED)
+ return ERR_PTR(-EAGAIN);
+
if (!*s)
flags &= ~LOOKUP_RCU;
if (flags & LOOKUP_RCU)
@@ -3129,7 +3134,6 @@ static const char *open_last_lookups(struct nameidata *nd,
struct inode *inode;
struct dentry *dentry;
const char *res;
- int error;
nd->flags |= op->intent;
@@ -3153,9 +3157,8 @@ static const char *open_last_lookups(struct nameidata *nd,
} else {
/* create side of things */
if (nd->flags & LOOKUP_RCU) {
- error = unlazy_walk(nd);
- if (unlikely(error))
- return ERR_PTR(error);
+ if (!try_to_unlazy(nd))
+ return ERR_PTR(-ECHILD);
}
audit_inode(nd->name, dir, AUDIT_INODE_PARENT);
/* trailing slashes? */
@@ -3164,9 +3167,7 @@ static const char *open_last_lookups(struct nameidata *nd,
}
if (open_flag & (O_CREAT | O_TRUNC | O_WRONLY | O_RDWR)) {
- error = mnt_want_write(nd->path.mnt);
- if (!error)
- got_write = true;
+ got_write = !mnt_want_write(nd->path.mnt);
/*
* do _not_ fail yet - we might not need that or fail with
* a different error; let lookup_open() decide; we'll be
@@ -3325,10 +3326,8 @@ static int do_tmpfile(struct nameidata *nd, unsigned flags,
audit_inode(nd->name, child, 0);
/* Don't check for other permissions, the inode was just created */
error = may_open(&path, 0, op->open_flag);
- if (error)
- goto out2;
- file->f_path.mnt = path.mnt;
- error = finish_open(file, child, NULL);
+ if (!error)
+ error = vfs_open(&path, file);
out2:
mnt_drop_write(path.mnt);
out:
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.