From 6fac94437a7d07f65bcc67a1a050ce0d40f9c5a0 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Tue, 28 Feb 2023 09:21:39 +0800 Subject: [PATCH] Make sure nd->path.mnt and nd->path.dentry are always valid pointers MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit stable inclusion from stable-v5.10.162 commit 0cf0ce8fb5b10d669072345ea855de112d0e0a43 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I6BTWC Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=v5.10.167&id=0cf0ce8fb5b10d669072345ea855de112d0e0a43 -------------------------------- [ Upstream commit 7d01ef7585c07afaf487759a48486228cd065726 ] 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 Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman Conflict： fs/namei.c Signed-off-by: Li Lingfeng Reviewed-by: Zhang Yi Reviewed-by: Wang Weiyang Signed-off-by: Jialin Zhang --- fs/namei.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index 98b5c4609f25..ce847021d304 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -533,6 +533,8 @@ 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; p->state = 0; @@ -607,6 +609,8 @@ 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 */ @@ -2250,8 +2254,6 @@ 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)) { -- GitLab