From 5096add84b9e96e2e0a9c72675c442fe5433388a Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Tue, 8 May 2007 00:26:04 -0700 Subject: [PATCH] proc: maps protection The /proc/pid/ "maps", "smaps", and "numa_maps" files contain sensitive information about the memory location and usage of processes. Issues: - maps should not be world-readable, especially if programs expect any kind of ASLR protection from local attackers. - maps cannot just be 0400 because "-D_FORTIFY_SOURCE=2 -O2" makes glibc check the maps when %n is in a *printf call, and a setuid(getuid()) process wouldn't be able to read its own maps file. (For reference see http://lkml.org/lkml/2006/1/22/150) - a system-wide toggle is needed to allow prior behavior in the case of non-root applications that depend on access to the maps contents. This change implements a check using "ptrace_may_attach" before allowing access to read the maps contents. To control this protection, the new knob /proc/sys/kernel/maps_protect has been added, with corresponding updates to the procfs documentation. [akpm@linux-foundation.org: build fixes] [akpm@linux-foundation.org: New sysctl numbers are old hat] Signed-off-by: Kees Cook Cc: Arjan van de Ven Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- CREDITS | 2 +- Documentation/filesystems/proc.txt | 7 +++++++ fs/proc/base.c | 4 ++++ fs/proc/internal.h | 2 ++ fs/proc/task_mmu.c | 17 ++++++++++++++++- fs/proc/task_nommu.c | 7 +++++++ kernel/sysctl.c | 11 +++++++++++ 7 files changed, 48 insertions(+), 2 deletions(-) diff --git a/CREDITS b/CREDITS index c5f819b..e71fdce 100644 --- a/CREDITS +++ b/CREDITS @@ -661,7 +661,7 @@ N: Kees Cook E: kees@outflux.net W: http://outflux.net/ P: 1024D/17063E6D 9FA3 C49C 23C9 D1BC 2E30 1975 1FFF 4BA9 1706 3E6D -D: Minor updates to SCSI code for the Communications type +D: Minor updates to SCSI types, added /proc/pid/maps protection S: (ask for current address) S: USA diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index 3f4b226..4f3e84c 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -1138,6 +1138,13 @@ determine whether or not they are still functioning properly. Because the NMI watchdog shares registers with oprofile, by disabling the NMI watchdog, oprofile may have more registers to utilize. +maps_protect +------------ + +Enables/Disables the protection of the per-process proc entries "maps" and +"smaps". When enabled, the contents of these files are visible only to +readers that are allowed to ptrace() the given process. + 2.4 /proc/sys/vm - The virtual memory subsystem ----------------------------------------------- diff --git a/fs/proc/base.c b/fs/proc/base.c index a721acf..17f7a7e 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -64,6 +64,7 @@ #include #include #include +#include #include #include #include @@ -123,6 +124,9 @@ struct pid_entry { NULL, &proc_info_file_operations, \ { .proc_read = &proc_##OTYPE } ) +int maps_protect; +EXPORT_SYMBOL(maps_protect); + static struct fs_struct *get_fs_struct(struct task_struct *task) { struct fs_struct *fs; diff --git a/fs/proc/internal.h b/fs/proc/internal.h index f771889..b215c35 100644 --- a/fs/proc/internal.h +++ b/fs/proc/internal.h @@ -37,6 +37,8 @@ do { \ extern int nommu_vma_show(struct seq_file *, struct vm_area_struct *); #endif +extern int maps_protect; + extern void create_seq_entry(char *name, mode_t mode, const struct file_operations *f); extern int proc_exe_link(struct inode *, struct dentry **, struct vfsmount **); extern int proc_tid_stat(struct task_struct *, char *); diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index 4008c06..c24d81a 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -3,6 +3,7 @@ #include #include #include +#include #include #include @@ -142,6 +143,9 @@ static int show_map_internal(struct seq_file *m, void *v, struct mem_size_stats dev_t dev = 0; int len; + if (maps_protect && !ptrace_may_attach(task)) + return -EACCES; + if (file) { struct inode *inode = vma->vm_file->f_path.dentry->d_inode; dev = inode->i_sb->s_dev; @@ -512,11 +516,22 @@ const struct file_operations proc_maps_operations = { #ifdef CONFIG_NUMA extern int show_numa_map(struct seq_file *m, void *v); +static int show_numa_map_checked(struct seq_file *m, void *v) +{ + struct proc_maps_private *priv = m->private; + struct task_struct *task = priv->task; + + if (maps_protect && !ptrace_may_attach(task)) + return -EACCES; + + return show_numa_map(m, v); +} + static struct seq_operations proc_pid_numa_maps_op = { .start = m_start, .next = m_next, .stop = m_stop, - .show = show_numa_map + .show = show_numa_map_checked }; static int numa_maps_open(struct inode *inode, struct file *file) diff --git a/fs/proc/task_nommu.c b/fs/proc/task_nommu.c index 7cddf6b..d8b8c71 100644 --- a/fs/proc/task_nommu.c +++ b/fs/proc/task_nommu.c @@ -2,6 +2,7 @@ #include #include #include +#include #include #include "internal.h" @@ -143,6 +144,12 @@ out: static int show_map(struct seq_file *m, void *_vml) { struct vm_list_struct *vml = _vml; + struct proc_maps_private *priv = m->private; + struct task_struct *task = priv->task; + + if (maps_protect && !ptrace_may_attach(task)) + return -EACCES; + return nommu_vma_show(m, vml->vma); } diff --git a/kernel/sysctl.c b/kernel/sysctl.c index c904748..f0664bd 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -76,6 +76,7 @@ extern int pid_max_min, pid_max_max; extern int sysctl_drop_caches; extern int percpu_pagelist_fraction; extern int compat_log; +extern int maps_protect; /* this is needed for the proc_dointvec_minmax for [fs_]overflow UID and GID */ static int maxolduid = 65535; @@ -603,6 +604,16 @@ static ctl_table kern_table[] = { .proc_handler = &proc_dointvec, }, #endif +#ifdef CONFIG_PROC_FS + { + .ctl_name = CTL_UNNUMBERED, + .procname = "maps_protect", + .data = &maps_protect, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = &proc_dointvec, + }, +#endif { .ctl_name = 0 } }; -- 1.8.2.3