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-rw-r--r--fs/namei.c89
-rw-r--r--fs/open.c6
-rw-r--r--include/linux/fcntl.h2
-rw-r--r--include/linux/namei.h1
-rw-r--r--include/uapi/linux/openat2.h4
5 files changed, 56 insertions, 46 deletions
diff --git a/fs/namei.c b/fs/namei.c
index 78443a85480a5a..de74ad2bc6e282 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:
diff --git a/fs/open.c b/fs/open.c
index 1e06e443a5651a..ca5444733acdeb 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -1091,6 +1091,12 @@ inline int build_open_flags(const struct open_how *how, struct open_flags *op)
lookup_flags |= LOOKUP_BENEATH;
if (how->resolve & RESOLVE_IN_ROOT)
lookup_flags |= LOOKUP_IN_ROOT;
+ if (how->resolve & RESOLVE_CACHED) {
+ /* Don't bother even trying for create/truncate/tmpfile open */
+ if (flags & (O_TRUNC | O_CREAT | O_TMPFILE))
+ return -EAGAIN;
+ lookup_flags |= LOOKUP_CACHED;
+ }
op->lookup_flags = lookup_flags;
return 0;
diff --git a/include/linux/fcntl.h b/include/linux/fcntl.h
index 921e750843e660..766fcd973bebac 100644
--- a/include/linux/fcntl.h
+++ b/include/linux/fcntl.h
@@ -19,7 +19,7 @@
/* List of all valid flags for the how->resolve argument: */
#define VALID_RESOLVE_FLAGS \
(RESOLVE_NO_XDEV | RESOLVE_NO_MAGICLINKS | RESOLVE_NO_SYMLINKS | \
- RESOLVE_BENEATH | RESOLVE_IN_ROOT)
+ RESOLVE_BENEATH | RESOLVE_IN_ROOT | RESOLVE_CACHED)
/* List of all open_how "versions". */
#define OPEN_HOW_SIZE_VER0 24 /* sizeof first published struct */
diff --git a/include/linux/namei.h b/include/linux/namei.h
index a4bb992623c411..b9605b2b46e714 100644
--- a/include/linux/namei.h
+++ b/include/linux/namei.h
@@ -46,6 +46,7 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT};
#define LOOKUP_NO_XDEV 0x040000 /* No mountpoint crossing. */
#define LOOKUP_BENEATH 0x080000 /* No escaping from starting point. */
#define LOOKUP_IN_ROOT 0x100000 /* Treat dirfd as fs root. */
+#define LOOKUP_CACHED 0x200000 /* Only do cached lookup */
/* LOOKUP_* flags which do scope-related checks based on the dirfd. */
#define LOOKUP_IS_SCOPED (LOOKUP_BENEATH | LOOKUP_IN_ROOT)
diff --git a/include/uapi/linux/openat2.h b/include/uapi/linux/openat2.h
index 58b1eb71136007..a5feb760494879 100644
--- a/include/uapi/linux/openat2.h
+++ b/include/uapi/linux/openat2.h
@@ -35,5 +35,9 @@ struct open_how {
#define RESOLVE_IN_ROOT 0x10 /* Make all jumps to "/" and ".."
be scoped inside the dirfd
(similar to chroot(2)). */
+#define RESOLVE_CACHED 0x20 /* Only complete if resolution can be
+ completed through cached lookup. May
+ return -EAGAIN if that's not
+ possible. */
#endif /* _UAPI_LINUX_OPENAT2_H */
generated by cgit 1.2.3-korg (git 2.39.0) at 2024-05-31 12:09:50 +0000