On Sat, Oct 11, 2014 at 05:58:08PM -0500, Eric Biggers wrote: > In path_init(), said commit added a call to read_seqcount_retry() after loading > the inode. I see two problems with this: > > - The read_seqcount_retry() isn't needed just to load the inode pointer, so > the change doesn't seem to accomplish anything. Huh? What's to guarantee that dentry hasn't become negative since the moment we'd fetched the seqcount? _That_ is the problem we are dealing with here - link_path_walk() relies on nd->inode being non-NULL. > - If the -ECHILD code path actually runs, the reference to the 'struct file' > can be leaked. Umm... That, OTOH, might be true, _if_ we could hit it on the path where nd->path comes from file (and descriptor table had been shared). Which could happen, if we could get d_drop() done to that sucker for some reason - other codepaths bumping the seqcount are impossible for pinned dentry (including that of an opened file). Which can, indeed, happen on something like NFS. OK, so all callers of path_init() should go to the same place where they go on link_path_walk() failure, like this. And that's probably what we want in backports; however, longer term we would be better off with a combined path_init + link_path_walk - all callers do exactly the same thing there... OK, that can be in a followup... Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx> --- diff --git a/fs/namei.c b/fs/namei.c index d20d579..0f64aa4 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1950,7 +1950,7 @@ static int path_lookupat(int dfd, const char *name, err = path_init(dfd, name, flags | LOOKUP_PARENT, nd, &base); if (unlikely(err)) - return err; + goto out; current->total_link_count = 0; err = link_path_walk(name, nd); @@ -1982,6 +1982,7 @@ static int path_lookupat(int dfd, const char *name, } } +out: if (base) fput(base); @@ -2301,7 +2302,7 @@ path_mountpoint(int dfd, const char *name, struct path *path, unsigned int flags err = path_init(dfd, name, flags | LOOKUP_PARENT, &nd, &base); if (unlikely(err)) - return err; + goto out; current->total_link_count = 0; err = link_path_walk(name, &nd); -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
