On Tue, 27 Jan 2015 00:00:54 +0300 Cyrill Gorcunov <gorcunov@xxxxxxxxx> wrote: > On Mon, Jan 26, 2015 at 02:47:31PM +0200, Kirill A. Shutemov wrote: > > On Fri, Jan 23, 2015 at 07:15:44PM -0800, 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. This is the main (actually only) justification for the patch, and it it far too thin. What does "not needed" mean. Why can't people just use /proc/pid/maps? > > > This patch moves the folder out from behind CHECKPOINT_RESTORE, and > > > removes the CAP_SYS_ADMIN restrictions. Following the links requires > > > the ability to ptrace the process in question, so this doesn't allow > > > an attacker to do anything they couldn't already do before. > > > > > > Signed-off-by: Calvin Owens <calvinowens@xxxxxx> > > > > Cc +linux-api@ > > Looks good to me, thanks! Though I would really appreciate if someone > from security camp take a look as well. hm, who's that. Kees comes to mind. And reviewers' task would be a heck of a lot easier if they knew what /proc/pid/map_files actually does. This: akpm3:/usr/src/25> grep -r map_files Documentation akpm3:/usr/src/25> does not help. The 640708a2cff7f81 changelog says: : This one behaves similarly to the /proc/<pid>/fd/ one - it contains : symlinks one for each mapping with file, the name of a symlink is : "vma->vm_start-vma->vm_end", the target is the file. Opening a symlink : results in a file that point exactly to the same inode as them vma's one. : : For example the ls -l of some arbitrary /proc/<pid>/map_files/ : : | lr-x------ 1 root root 64 Aug 26 06:40 7f8f80403000-7f8f80404000 -> /lib64/libc-2.5.so : | lr-x------ 1 root root 64 Aug 26 06:40 7f8f8061e000-7f8f80620000 -> /lib64/libselinux.so.1 : | lr-x------ 1 root root 64 Aug 26 06:40 7f8f80826000-7f8f80827000 -> /lib64/libacl.so.1.1.0 : | lr-x------ 1 root root 64 Aug 26 06:40 7f8f80a2f000-7f8f80a30000 -> /lib64/librt-2.5.so : | lr-x------ 1 root root 64 Aug 26 06:40 7f8f80a30000-7f8f80a4c000 -> /lib64/ld-2.5.so afacit this info is also available in /proc/pid/maps, so things shouldn't get worse if the /proc/pid/map_files permissions are at least as restrictive as the /proc/pid/maps permissions. Is that the case? (Please add to changelog). There's one other problem here: we're assuming that the map_files implementation doesn't have bugs. If it does have bugs then relaxing permissions like this will create new vulnerabilities. And the map_files implementation is surprisingly complex. Is it bug-free? -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
