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SubjectRe: [PATCH] mm/nommu.c: Fix improperly call of security API in mmap
On Fri, 20 Nov 2009 14:32:02 -0500
Eric Paris <eparis@redhat.com> wrote:

> On Fri, 2009-11-20 at 17:54 +0000, David Howells wrote:
> > Andrew Morton <akpm@linux-foundation.org> wrote:
> >
> > > I'll hold off, as Eric is preparing an alternative for "the end of this
> > > week". If that doesn't work out, we can add
> > > nommu-ignore-the-address-parameter-in-the-file_mmap-security-check.patch
> > > to 2.6.32.1, OK?
> >
> > I'll be on holiday next week.
>
> Can we give this a whirl? I can't even seem to make a config not select
> MMU, so it isn't even compile tested in that case. If it is good, I'll
> send as a clean message for James Morris to take through the security
> tree....
>

You'll need a cross-compiler.

> commit 58c728c7f9c2c8e2c62f7dfda3e10f77524c4379
> Author: Eric Paris <eparis@redhat.com>
> Date: Fri Nov 20 14:23:57 2009 -0500
>
> 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@redhat.com>

Patch doesn't apply to current mainline for some reason. I fixed that
up and checked that the affected files compile OK on superh.

The patch adds trailing whitespace. If only we had a tool for that ;)

diff -puN include/linux/security.h~mm-nommuc-fix-improperly-call-of-security-api-in-mmap include/linux/security.h
--- a/include/linux/security.h~mm-nommuc-fix-improperly-call-of-security-api-in-mmap
+++ a/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_ADDR_ONLY 0x01
+#define SECURITY_MMAP_NOT_ADDR 0x02
+
struct ctl_table;
struct audit_krule;

@@ -69,7 +73,7 @@ extern int cap_inode_need_killpriv(struc
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);
@@ -593,6 +597,8 @@ static inline void security_free_mnt_opt
* @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 what security checks should be done
* Return 0 if permission is granted.
* @file_mprotect:
* Check permissions before changing memory access permissions.
@@ -1535,7 +1541,7 @@ 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);
@@ -1804,7 +1810,7 @@ void security_file_free(struct file *fil
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);
@@ -2300,9 +2306,9 @@ static inline int security_file_mmap(str
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 -puN mm/mmap.c~mm-nommuc-fix-improperly-call-of-security-api-in-mmap mm/mmap.c
--- a/mm/mmap.c~mm-nommuc-fix-improperly-call-of-security-api-in-mmap
+++ a/mm/mmap.c
@@ -1668,7 +1668,8 @@ static int expand_downwards(struct vm_ar
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_ADDR_ONLY);
if (error)
return error;

@@ -2009,7 +2010,8 @@ unsigned long do_brk(unsigned long addr,
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_ADDR_ONLY);
if (error)
return error;

diff -puN mm/mremap.c~mm-nommuc-fix-improperly-call-of-security-api-in-mmap mm/mremap.c
--- a/mm/mremap.c~mm-nommuc-fix-improperly-call-of-security-api-in-mmap
+++ a/mm/mremap.c
@@ -313,7 +313,8 @@ unsigned long do_mremap(unsigned long ad
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_ADDR_ONLY);
if (ret)
goto out;

@@ -421,7 +422,8 @@ unsigned long do_mremap(unsigned long ad
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_ADDR_ONLY);
if (ret)
goto out;
}
diff -puN mm/nommu.c~mm-nommuc-fix-improperly-call-of-security-api-in-mmap mm/nommu.c
--- a/mm/nommu.c~mm-nommuc-fix-improperly-call-of-security-api-in-mmap
+++ a/mm/nommu.c
@@ -974,7 +974,8 @@ static int validate_mmap_request(struct
}

/* 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_NOT_ADDR);
if (ret < 0)
return ret;

diff -puN security/commoncap.c~mm-nommuc-fix-improperly-call-of-security-api-in-mmap security/commoncap.c
--- a/security/commoncap.c~mm-nommuc-fix-improperly-call-of-security-api-in-mmap
+++ a/security/commoncap.c
@@ -992,7 +992,7 @@ int cap_vm_enough_memory(struct mm_struc
* @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
@@ -1001,11 +1001,12 @@ int cap_vm_enough_memory(struct mm_struc
*/
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_NOT_ADDR) &&
+ (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 -puN security/security.c~mm-nommuc-fix-improperly-call-of-security-api-in-mmap security/security.c
--- a/security/security.c~mm-nommuc-fix-improperly-call-of-security-api-in-mmap
+++ a/security/security.c
@@ -637,9 +637,9 @@ int security_file_ioctl(struct file *fil

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)
{
- return security_ops->file_mmap(file, reqprot, prot, flags, addr, addr_only);
+ return security_ops->file_mmap(file, reqprot, prot, flags, addr, sec_flags);
}

int security_file_mprotect(struct vm_area_struct *vma, unsigned long reqprot,
diff -puN security/selinux/hooks.c~mm-nommuc-fix-improperly-call-of-security-api-in-mmap security/selinux/hooks.c
--- a/security/selinux/hooks.c~mm-nommuc-fix-improperly-call-of-security-api-in-mmap
+++ a/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
* 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_NOT_ADDR) &&
+ (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
}

/* 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_ADDR_ONLY))
return rc;

if (selinux_checkreqprot)
_


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