[PATCH 14/20] fuse_dentry_revalidate(): use stable parent inode and name passed by caller

Al Viro
2025-01-10T02:43:06Z

No need to mess with dget_parent() for the former; for the latter we really should
not rely upon ->d_name.name remaining stable - it's a real-life UAF.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
fs/fuse/dir.c | 11 +++--------
1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index d9e9f26917eb..7e93a8470c36 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -196,7 +196,6 @@ static int fuse_dentry_revalidate(struct inode *dir, const struct qstr *name,
struct dentry *entry, unsigned int flags)
{
struct inode *inode;
- struct dentry *parent;
struct fuse_mount *fm;
struct fuse_inode *fi;
int ret;
@@ -228,11 +227,9 @@ static int fuse_dentry_revalidate(struct inode *dir, const struct qstr *name,

attr_version = fuse_get_attr_version(fm->fc);

- parent = dget_parent(entry);
- fuse_lookup_init(fm->fc, &args, get_node_id(d_inode(parent)),
- &entry->d_name, &outarg);
+ fuse_lookup_init(fm->fc, &args, get_node_id(dir),
+ name, &outarg);
ret = fuse_simple_request(fm, &args);
- dput(parent);
/* Zero nodeid is same as -ENOENT */
if (!ret && !outarg.nodeid)
ret = -ENOENT;
@@ -266,9 +263,7 @@ static int fuse_dentry_revalidate(struct inode *dir, const struct qstr *name,
if (test_bit(FUSE_I_INIT_RDPLUS, &fi->state))
return -ECHILD;
} else if (test_and_clear_bit(FUSE_I_INIT_RDPLUS, &fi->state)) {
- parent = dget_parent(entry);
- fuse_advise_use_readdirplus(d_inode(parent));
- dput(parent);
+ fuse_advise_use_readdirplus(dir);
}
}
ret = 1;
--
2.39.5