Add proc.umask kernel parameter. It can be used to restrict permissions on the numerical directories in the root of a proc filesystem, i.e. the directories containing process specific information.
E.g. add proc.umask=077 to your kernel command line and all users except root can only see their own process details (like command line parameters) with ps or top. It can be useful to add a bit of privacy to multi-user servers. The patch has been inspired by a similar feature in GrSecurity. It could have also been implemented as a mount option to procfs, but at a higher cost and no apparent benefit -- changes to this umask are not supposed to happen very often. Actually, the previous incarnation of this patch was implemented as a half-assed mount option, but I didn't know then how easy it is to add a kernel parameter. Comments about usefulness or implementation are very welcome. Thanks, Rene --- linux-2.6.11-rc4/fs/proc/base.c~ 2005-02-11 21:16:13.000000000 +0100 +++ linux-2.6.11-rc4/fs/proc/base.c 2005-02-11 23:38:17.000000000 +0100 @@ -32,8 +32,14 @@ #include <linux/mount.h> #include <linux/security.h> #include <linux/ptrace.h> +#include <linux/module.h> +#include <linux/moduleparam.h> #include "internal.h" +static umode_t umask = 0; +module_param(umask, ushort, 0); +MODULE_PARM_DESC(umask, "umask for the numerical directories in /proc"); + /* * For hysterical raisins we keep the same inumbers as in the old procfs. * Feel free to change the macro below - just keep the range distinct from @@ -1369,7 +1375,7 @@ static struct dentry *proc_pident_lookup goto out; ei = PROC_I(inode); - inode->i_mode = p->mode; + inode->i_mode = p->mode & ~(umask & S_IRWXUGO); /* * Yes, it does not scale. And it should not. Don't add * new entries into /proc/<tgid>/ without very good reasons. @@ -1699,7 +1705,7 @@ struct dentry *proc_pid_lookup(struct in put_task_struct(task); goto out; } - inode->i_mode = S_IFDIR|S_IRUGO|S_IXUGO; + inode->i_mode = S_IFDIR | ((S_IRUGO|S_IXUGO) & ~umask); inode->i_op = &proc_tgid_base_inode_operations; inode->i_fop = &proc_tgid_base_operations; inode->i_nlink = 3; @@ -1754,7 +1760,7 @@ static struct dentry *proc_task_lookup(s if (!inode) goto out_drop_task; - inode->i_mode = S_IFDIR|S_IRUGO|S_IXUGO; + inode->i_mode = S_IFDIR | ((S_IRUGO|S_IXUGO) & ~umask); inode->i_op = &proc_tid_base_inode_operations; inode->i_fop = &proc_tid_base_operations; inode->i_nlink = 3; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/