diff options
| author | Tavis Ormandy <taviso@cmpxchg8b.com> | 2010-12-09 15:29:42 +0100 |
|---|---|---|
| committer | Willy Tarreau <w@1wt.eu> | 2011-02-09 22:15:39 +0100 |
| commit | 041f1a0d35e62f447e007f665e437a59e5945e77 (patch) | |
| tree | 93818d83cd2f624a64b6f9e0d8c42da87467b07b | |
| parent | ab42f1f2ba5bea8d266ed383438ad5652617b366 (diff) | |
install_special_mapping skips security_file_mmap check.
commit 462e635e5b73ba9a4c03913b77138cd57ce4b050 upstream.
The install_special_mapping routine (used, for example, to setup the
vdso) skips the security check before insert_vm_struct, allowing a local
attacker to bypass the mmap_min_addr security restriction by limiting
the available pages for special mappings.
bprm_mm_init() also skips the check, and although I don't think this can
be used to bypass any restrictions, I don't see any reason not to have
the security check.
$ uname -m
x86_64
$ cat /proc/sys/vm/mmap_min_addr
65536
$ cat install_special_mapping.s
section .bss
resb BSS_SIZE
section .text
global _start
_start:
mov eax, __NR_pause
int 0x80
$ nasm -D__NR_pause=29 -DBSS_SIZE=0xfffed000 -f elf -o install_special_mapping.o install_special_mapping.s
$ ld -m elf_i386 -Ttext=0x10000 -Tbss=0x11000 -o install_special_mapping install_special_mapping.o
$ ./install_special_mapping &
[1] 14303
$ cat /proc/14303/maps
0000f000-00010000 r-xp 00000000 00:00 0 [vdso]
00010000-00011000 r-xp 00001000 00:19 2453665 /home/taviso/install_special_mapping
00011000-ffffe000 rwxp 00000000 00:00 0 [stack]
It's worth noting that Red Hat are shipping with mmap_min_addr set to
4096.
Signed-off-by: Tavis Ormandy <taviso@google.com>
Acked-by: Kees Cook <kees@ubuntu.com>
Acked-by: Robert Swiecki <swiecki@google.com>
[ Changed to not drop the error code - akpm ]
Reviewed-by: James Morris <jmorris@namei.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Willy Tarreau <w@1wt.eu>
| -rw-r--r-- | fs/exec.c | 5 | ||||
| -rw-r--r-- | mm/mmap.c | 16 |
2 files changed, 17 insertions, 4 deletions
diff --git a/fs/exec.c b/fs/exec.c index fc30de0d121..12e7ad2491b 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -257,6 +257,11 @@ static int __bprm_mm_init(struct linux_binprm *bprm) vma->vm_flags = VM_STACK_FLAGS; vma->vm_page_prot = vm_get_page_prot(vma->vm_flags); + + err = security_file_mmap(NULL, 0, 0, 0, vma->vm_start, 1); + if (err) + goto err; + err = insert_vm_struct(mm, vma); if (err) { up_write(&mm->mmap_sem); diff --git a/mm/mmap.c b/mm/mmap.c index 17d640d33df..707ce0f74e6 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -2253,6 +2253,7 @@ int install_special_mapping(struct mm_struct *mm, unsigned long addr, unsigned long len, unsigned long vm_flags, struct page **pages) { + int ret; struct vm_area_struct *vma; vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL); @@ -2269,14 +2270,21 @@ int install_special_mapping(struct mm_struct *mm, vma->vm_ops = &special_mapping_vmops; vma->vm_private_data = pages; - if (unlikely(insert_vm_struct(mm, vma))) { - kmem_cache_free(vm_area_cachep, vma); - return -ENOMEM; - } + ret = security_file_mmap(NULL, 0, 0, 0, vma->vm_start, 1); + if (ret) + goto out; + + ret = insert_vm_struct(mm, vma); + if (ret) + goto out; mm->total_vm += len >> PAGE_SHIFT; return 0; + +out: + kmem_cache_free(vm_area_cachep, vma); + return ret; } static DEFINE_MUTEX(mm_all_locks_mutex); |