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authorAl Viro <viro@zeniv.linux.org.uk>2021-04-06 12:33:07 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2021-04-06 12:33:07 -0400
commit7d01ef7585c07afaf487759a48486228cd065726 (patch)
tree32844388a12c3463c659eb7f9915a78261bdbca3 /fs/namei.c
parent7f6c411c9b50cfab41cc798e003eff27608c7016 (diff)
downloadlinux-7d01ef7585c07afaf487759a48486228cd065726.tar.bz2
Make sure nd->path.mnt and nd->path.dentry are always valid pointers
Initialize them in set_nameidata() and make sure that terminate_walk() clears them once the pointers become potentially invalid (i.e. we leave RCU mode or drop them in non-RCU one). Currently we have "path_init() always initializes them and nobody accesses them outside of path_init()/terminate_walk() segments", which is asking for trouble. With that change we would have nd->path.{mnt,dentry} 1) always valid - NULL or pointing to currently allocated objects. 2) non-NULL while we are successfully walking 3) NULL when we are not walking at all 4) contributing to refcounts whenever non-NULL outside of RCU mode. Fixes: 6c6ec2b0a3e0 ("fs: add support for LOOKUP_CACHED") Reported-by: syzbot+c88a7030da47945a3cc3@syzkaller.appspotmail.com Tested-by: Christian Brauner <christian.brauner@ubuntu.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/namei.c')
-rw-r--r--fs/namei.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/fs/namei.c b/fs/namei.c
index 216f16e74351..fc8760d4314e 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -579,6 +579,8 @@ static void set_nameidata(struct nameidata *p, int dfd, struct filename *name)
p->stack = p->internal;
p->dfd = dfd;
p->name = name;
+ p->path.mnt = NULL;
+ p->path.dentry = NULL;
p->total_link_count = old ? old->total_link_count : 0;
p->saved = old;
current->nameidata = p;
@@ -652,6 +654,8 @@ static void terminate_walk(struct nameidata *nd)
rcu_read_unlock();
}
nd->depth = 0;
+ nd->path.mnt = NULL;
+ nd->path.dentry = NULL;
}
/* path_put is needed afterwards regardless of success or failure */
@@ -2322,8 +2326,6 @@ static const char *path_init(struct nameidata *nd, unsigned flags)
}
nd->root.mnt = NULL;
- nd->path.mnt = NULL;
- nd->path.dentry = NULL;
/* Absolute pathname -- fetch the root (LOOKUP_IN_ROOT uses nd->dfd). */
if (*s == '/' && !(flags & LOOKUP_IN_ROOT)) {