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Message-ID: <20091205032600.19963.93690.stgit@paris.rdu.redhat.com>
Date: Fri, 04 Dec 2009 22:26:00 -0500
From: Eric Paris <eparis@...hat.com>
To: linux-security-module@...r.kernel.org,
linux-kernel@...r.kernel.org,
uclinux-dist-devel@...ckfin.uclinux.org
Cc: eparis@...hat.com, dhowells@...hat.com, akpm@...ux-foundation.org,
gyang@...ckfin.uclinux.org, john.johansen@...onical.com
Subject: [PATCH] security: do not check mmap_min_addr on nommu systems
nommu systems can do anything with memory they please and so they already
win. mmap_min_addr is the least of their worries. Currently the
mmap_min_addr implementation is problamatic on such systems. This patch
changes the addr_only argument to be a flags which can take the arguments
for addr_only or not_addr. LSMs then need to properly implement these two
flags.
Signed-off-by: Eric Paris <eparis@...hat.com>
---
include/linux/security.h | 20 ++++++++++++++------
mm/mmap.c | 6 ++++--
mm/mremap.c | 6 ++++--
mm/nommu.c | 3 ++-
security/commoncap.c | 7 ++++---
security/security.c | 5 +++--
security/selinux/hooks.c | 9 +++++----
7 files changed, 36 insertions(+), 20 deletions(-)
diff --git a/include/linux/security.h b/include/linux/security.h
index 9c3a43b..3438d82 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -43,6 +43,10 @@
#define SECURITY_CAP_NOAUDIT 0
#define SECURITY_CAP_AUDIT 1
+/* sec_flags for security_file_mmap */
+#define SECURITY_MMAP_ONLY_ADDR_CHECK 0x01
+#define SECURITY_MMAP_SKIP_ADDR_CHECK 0x02
+
struct ctl_table;
struct audit_krule;
@@ -69,7 +73,7 @@ extern int cap_inode_need_killpriv(struct dentry *dentry);
extern int cap_inode_killpriv(struct dentry *dentry);
extern int cap_file_mmap(struct file *file, unsigned long reqprot,
unsigned long prot, unsigned long flags,
- unsigned long addr, unsigned long addr_only);
+ unsigned long addr, unsigned long sec_flags);
extern int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags);
extern int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
unsigned long arg4, unsigned long arg5);
@@ -604,11 +608,15 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
* Return 0 if permission is granted.
* @file_mmap :
* Check permissions for a mmap operation. The @file may be NULL, e.g.
- * if mapping anonymous memory.
+ * if mapping anonymous memory. This actually performs 2 seperate types
+ * of checks. It first checks permissions on the file in question (if
+ * it exists) and it also checks if the address is allowed.
* @file contains the file structure for file to map (may be NULL).
* @reqprot contains the protection requested by the application.
* @prot contains the protection that will be applied by the kernel.
* @flags contains the operational flags.
+ * @addr address vm will map to
+ * @sec_flags which of the 2 types of checks should (not) be performed
* Return 0 if permission is granted.
* @file_mprotect:
* Check permissions before changing memory access permissions.
@@ -1556,7 +1564,7 @@ struct security_operations {
int (*file_mmap) (struct file *file,
unsigned long reqprot, unsigned long prot,
unsigned long flags, unsigned long addr,
- unsigned long addr_only);
+ unsigned long sec_flags);
int (*file_mprotect) (struct vm_area_struct *vma,
unsigned long reqprot,
unsigned long prot);
@@ -1826,7 +1834,7 @@ void security_file_free(struct file *file);
int security_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
int security_file_mmap(struct file *file, unsigned long reqprot,
unsigned long prot, unsigned long flags,
- unsigned long addr, unsigned long addr_only);
+ unsigned long addr, unsigned long sec_flags);
int security_file_mprotect(struct vm_area_struct *vma, unsigned long reqprot,
unsigned long prot);
int security_file_lock(struct file *file, unsigned int cmd);
@@ -2323,9 +2331,9 @@ static inline int security_file_mmap(struct file *file, unsigned long reqprot,
unsigned long prot,
unsigned long flags,
unsigned long addr,
- unsigned long addr_only)
+ unsigned long sec_flags)
{
- return cap_file_mmap(file, reqprot, prot, flags, addr, addr_only);
+ return cap_file_mmap(file, reqprot, prot, flags, addr, sec_flags);
}
static inline int security_file_mprotect(struct vm_area_struct *vma,
diff --git a/mm/mmap.c b/mm/mmap.c
index b6312d2..c1adcd3 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1665,7 +1665,8 @@ static int expand_downwards(struct vm_area_struct *vma,
return -ENOMEM;
address &= PAGE_MASK;
- error = security_file_mmap(NULL, 0, 0, 0, address, 1);
+ error = security_file_mmap(NULL, 0, 0, 0, address,
+ SECURITY_MMAP_ONLY_ADDR_CHECK);
if (error)
return error;
@@ -2006,7 +2007,8 @@ unsigned long do_brk(unsigned long addr, unsigned long len)
if (is_hugepage_only_range(mm, addr, len))
return -EINVAL;
- error = security_file_mmap(NULL, 0, 0, 0, addr, 1);
+ error = security_file_mmap(NULL, 0, 0, 0, addr,
+ SECURITY_MMAP_ONLY_ADDR_CHECK);
if (error)
return error;
diff --git a/mm/mremap.c b/mm/mremap.c
index d6740a1..8f88547 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -313,7 +313,8 @@ unsigned long do_mremap(unsigned long addr,
if ((addr <= new_addr) && (addr+old_len) > new_addr)
goto out;
- ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
+ ret = security_file_mmap(NULL, 0, 0, 0, new_addr,
+ SECURITY_MMAP_ONLY_ADDR_CHECK);
if (ret)
goto out;
@@ -421,7 +422,8 @@ unsigned long do_mremap(unsigned long addr,
goto out;
}
- ret = security_file_mmap(NULL, 0, 0, 0, new_addr, 1);
+ ret = security_file_mmap(NULL, 0, 0, 0, new_addr,
+ SECURITY_MMAP_ONLY_ADDR_CHECK);
if (ret)
goto out;
}
diff --git a/mm/nommu.c b/mm/nommu.c
index 9876fa0..0c0364f 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -974,7 +974,8 @@ static int validate_mmap_request(struct file *file,
}
/* allow the security API to have its say */
- ret = security_file_mmap(file, reqprot, prot, flags, addr, 0);
+ ret = security_file_mmap(file, reqprot, prot, flags, 0,
+ SECURITY_MMAP_SKIP_ADDR_CHECK);
if (ret < 0)
return ret;
diff --git a/security/commoncap.c b/security/commoncap.c
index f800fdb..193e9fa 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -924,7 +924,7 @@ int cap_vm_enough_memory(struct mm_struct *mm, long pages)
* @prot: unused
* @flags: unused
* @addr: address attempting to be mapped
- * @addr_only: unused
+ * @sec_flags: should the addr be checked?
*
* If the process is attempting to map memory below mmap_min_addr they need
* CAP_SYS_RAWIO. The other parameters to this function are unused by the
@@ -933,11 +933,12 @@ int cap_vm_enough_memory(struct mm_struct *mm, long pages)
*/
int cap_file_mmap(struct file *file, unsigned long reqprot,
unsigned long prot, unsigned long flags,
- unsigned long addr, unsigned long addr_only)
+ unsigned long addr, unsigned long sec_flags)
{
int ret = 0;
- if (addr < dac_mmap_min_addr) {
+ if (!(sec_flags & SECURITY_MMAP_SKIP_ADDR_CHECK) &&
+ (addr < dac_mmap_min_addr)) {
ret = cap_capable(current, current_cred(), CAP_SYS_RAWIO,
SECURITY_CAP_AUDIT);
/* set PF_SUPERPRIV if it turns out we allow the low mmap */
diff --git a/security/security.c b/security/security.c
index b6e43a1..fd2d450 100644
--- a/security/security.c
+++ b/security/security.c
@@ -677,11 +677,12 @@ int security_file_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
int security_file_mmap(struct file *file, unsigned long reqprot,
unsigned long prot, unsigned long flags,
- unsigned long addr, unsigned long addr_only)
+ unsigned long addr, unsigned long sec_flags)
{
int ret;
- ret = security_ops->file_mmap(file, reqprot, prot, flags, addr, addr_only);
+ ret = security_ops->file_mmap(file, reqprot, prot, flags, addr,
+ sec_flags);
if (ret)
return ret;
return ima_file_mmap(file, prot);
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 9688ccc..87bdc02 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -3043,7 +3043,7 @@ error:
static int selinux_file_mmap(struct file *file, unsigned long reqprot,
unsigned long prot, unsigned long flags,
- unsigned long addr, unsigned long addr_only)
+ unsigned long addr, unsigned long sec_flags)
{
int rc = 0;
u32 sid = current_sid();
@@ -3054,7 +3054,8 @@ static int selinux_file_mmap(struct file *file, unsigned long reqprot,
* at bad behaviour/exploit that we always want to get the AVC, even
* if DAC would have also denied the operation.
*/
- if (addr < CONFIG_LSM_MMAP_MIN_ADDR) {
+ if (!(sec_flags & SECURITY_MMAP_SKIP_ADDR_CHECK) &&
+ (addr < CONFIG_LSM_MMAP_MIN_ADDR)) {
rc = avc_has_perm(sid, sid, SECCLASS_MEMPROTECT,
MEMPROTECT__MMAP_ZERO, NULL);
if (rc)
@@ -3062,8 +3063,8 @@ static int selinux_file_mmap(struct file *file, unsigned long reqprot,
}
/* do DAC check on address space usage */
- rc = cap_file_mmap(file, reqprot, prot, flags, addr, addr_only);
- if (rc || addr_only)
+ rc = cap_file_mmap(file, reqprot, prot, flags, addr, sec_flags);
+ if (rc || (sec_flags & SECURITY_MMAP_ONLY_ADDR_CHECK))
return rc;
if (selinux_checkreqprot)
--
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