diff options
| author | Eric Paris <eparis@redhat.com> | 2007-11-26 18:47:40 -0500 |
|---|---|---|
| committer | James Morris <jmorris@namei.org> | 2007-12-06 00:25:10 +1100 |
| commit | 7cd94146cd504016315608e297219f9fb7b1413b (patch) | |
| tree | 1d118d6af0a6d3efb9be66f7305827aee2ceffea | |
| parent | 8869477a49c3e99def1fcdadd6bbc407fea14b45 (diff) | |
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>
| -rw-r--r-- | include/linux/mm.h | 16 | ||||
| -rw-r--r-- | mm/mmap.c | 3 | ||||
| -rw-r--r-- | mm/nommu.c | 3 |
3 files changed, 22 insertions, 0 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index 520238cbae5d..1b7b95c67aca 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -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; @@ -513,6 +514,21 @@ static inline void set_page_links(struct page *page, enum zone_type zone, } /* + * 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() */ #include <linux/vmstat.h> diff --git a/mm/mmap.c b/mm/mmap.c index 938313c76d02..f4cfc6ac08db 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -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; diff --git a/mm/nommu.c b/mm/nommu.c index 35622c590925..b989cb928a7c 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -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, |