Messages in this thread | | | Date | Wed, 23 Jan 2013 22:55:24 +0000 | From | Al Viro <> | Subject | [tracepoint] cargo-culting considered harmful... |
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In samples/tracepoints/tracepoint-probe-sample.c: /* * Here the caller only guarantees locking for struct file and struct inode. * Locking must therefore be done in the probe to use the dentry. */ static void probe_subsys_event(void *ignore, struct inode *inode, struct file *file) { path_get(&file->f_path); dget(file->f_path.dentry); printk(KERN_INFO "Event is encountered with filename %s\n", file->f_path.dentry->d_name.name); dput(file->f_path.dentry); path_put(&file->f_path); }
note that * file->f_path is already pinned down by open(), path_get() does not provide anything extra. * file->f_path.dentry is already pinned by open() *and* path_get() just above that dget(). * ->d_name.name *IS* *NOT* *PROTECTED* by pinning dentry down, whether it's done once or thrice.
I do realize that it's just an example, but perhaps we should rename that file to match the contents? The only question is whether it should be git mv samples/tracepoints/{tracepoint-probe-sample,cargo-cult}.c or git mv samples cargo-cult...
Al, seriously peeved.
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