diff options
| author | Tavis Ormandy <taviso@cmpxchg8b.com> | 2010-12-09 15:29:42 +0100 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-12-15 12:30:36 -0800 |
| commit | 462e635e5b73ba9a4c03913b77138cd57ce4b050 (patch) | |
| tree | 6ff0e84eecc6252d41d7c08730018c0149e7227f /fs/exec.c | |
| parent | 0fcdcfbbc98f70f559e4b36773a69972489a6d8f (diff) | |
| download | lwn-462e635e5b73ba9a4c03913b77138cd57ce4b050.tar.gz lwn-462e635e5b73ba9a4c03913b77138cd57ce4b050.zip | |
install_special_mapping skips security_file_mmap check.
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>
Diffstat (limited to 'fs/exec.c')
| -rw-r--r-- | fs/exec.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/fs/exec.c b/fs/exec.c index d68c378a3137..c62efcb959c7 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -275,6 +275,11 @@ static int __bprm_mm_init(struct linux_binprm *bprm) vma->vm_flags = VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP; vma->vm_page_prot = vm_get_page_prot(vma->vm_flags); INIT_LIST_HEAD(&vma->anon_vma_chain); + + err = security_file_mmap(NULL, 0, 0, 0, vma->vm_start, 1); + if (err) + goto err; + err = insert_vm_struct(mm, vma); if (err) goto err; |