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| author |   Al Viro <viro@zeniv.linux.org.uk> | 2021-04-06 12:33:07 -0400 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2021-04-06 12:33:07 -0400 |
| commit | 7d01ef7585c07afaf487759a48486228cd065726 (patch) | |
| tree | 32844388a12c3463c659eb7f9915a78261bdbca3 /fs/namei.c | |
| parent | hostfs: fix memory handling in follow_link() (diff) | |
| download | linux-dev-7d01ef7585c07afaf487759a48486228cd065726.tar.xz linux-dev-7d01ef7585c07afaf487759a48486228cd065726.zip | |
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.c | 6 |
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)) { |