Messages in this thread | | | Subject | Re: [PATCH v5] procfs: Always expose /proc/<pid>/map_files/ and make it readable | From | Joe Perches <> | Date | Mon, 18 May 2015 20:29:20 -0700 |
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On Mon, 2015-05-18 at 20:10 -0700, Calvin Owens wrote: > Currently, /proc/<pid>/map_files/ is restricted to CAP_SYS_ADMIN, and > is only exposed if CONFIG_CHECKPOINT_RESTORE is set. This interface is > very useful for enumerating the files mapped into a process when the > more verbose information in /proc/<pid>/maps is not needed. It also > allows access to file descriptors for files that have been deleted and > closed but are still mmapped into a process, which can be very useful > for introspection and debugging.
style trivia:
> diff --git a/fs/proc/base.c b/fs/proc/base.c [] > +/* > + * Enforce stronger PTRACE_MODE_ATTACH permissions on the symlinks under > + * /proc/<pid>/map_files, since these links may refer to deleted or O_TMPFILE > + * files that users might assume are inaccessible regardless of their > + * ownership/permissions. > + */ > +static void *proc_map_files_follow_link(struct dentry *dentry, struct nameidata *nd) > +{ > + struct inode *inode = d_inode(dentry); > + struct task_struct *task; > + int allowed = 0; > + > + task = get_proc_task(inode); > + if (task) { > + allowed = ptrace_may_access(task, PTRACE_MODE_ATTACH); > + put_task_struct(task); > + } else { > + return ERR_PTR(-ESRCH); > + } > + > + if (!allowed) > + return ERR_PTR(-EACCES); > + > + return proc_pid_follow_link(dentry, nd); > +}
It'd perhaps be clearer to read this with an immediate return after a failure in get_proc_task.
Maybe something like (move initializations as desired):
static void *proc_map_files_follow_link(struct dentry *dentry, struct nameidata *nd) { int allowed; struct iode *inode = d_inode(dentry); struct task_struct task = get_proc_task(inode);
if (!task) return ERR_PTR(-ESRCH);
allowed = ptrace_may_access(task, PTRACE_MODE_ATTACH);
put_task_struct(task);
if (!allowed) return ERR_PTR(-EACCES);
return proc_pic_follow_link(dentry, nd); }
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