Security: round mmap hint address above mmap_min_addr

If mmap_min_addr is set and a process attempts to mmap (not fixed) with a
non-null hint address less than mmap_min_addr the mapping will fail the
security checks.  Since this is just a hint address this patch will round
such a hint address above mmap_min_addr.

gcj was found to try to be very frugal with vm usage and give hint addresses
in the 8k-32k range.  Without this patch all such programs failed and with
the patch they happily get a higher address.

This patch is wrappad in CONFIG_SECURITY since mmap_min_addr doesn't exist
without it and there would be no security check possible no matter what.  So
we should not bother compiling in this rounding if it is just a waste of
time.

Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
This commit is contained in:
Eric Paris 2007-11-26 18:47:40 -05:00 committed by James Morris
parent 8869477a49
commit 7cd94146cd
3 changed files with 22 additions and 0 deletions

View file

@ -12,6 +12,7 @@
#include <linux/prio_tree.h>
#include <linux/debug_locks.h>
#include <linux/mm_types.h>
#include <linux/security.h>
struct mempolicy;
struct anon_vma;
@ -512,6 +513,21 @@ static inline void set_page_links(struct page *page, enum zone_type zone,
set_page_section(page, pfn_to_section_nr(pfn));
}
/*
* If a hint addr is less than mmap_min_addr change hint to be as
* low as possible but still greater than mmap_min_addr
*/
static inline unsigned long round_hint_to_min(unsigned long hint)
{
#ifdef CONFIG_SECURITY
hint &= PAGE_MASK;
if (((void *)hint != NULL) &&
(hint < mmap_min_addr))
return PAGE_ALIGN(mmap_min_addr);
#endif
return hint;
}
/*
* Some inline functions in vmstat.h depend on page_zone()
*/

View file

@ -912,6 +912,9 @@ unsigned long do_mmap_pgoff(struct file * file, unsigned long addr,
if (!len)
return -EINVAL;
if (!(flags & MAP_FIXED))
addr = round_hint_to_min(addr);
error = arch_mmap_check(addr, len, flags);
if (error)
return error;

View file

@ -829,6 +829,9 @@ unsigned long do_mmap_pgoff(struct file *file,
void *result;
int ret;
if (!(flags & MAP_FIXED))
addr = round_hint_to_min(addr);
/* decide whether we should attempt the mapping, and if so what sort of
* mapping */
ret = validate_mmap_request(file, addr, len, prot, flags, pgoff,