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authorTavis Ormandy <taviso@cmpxchg8b.com>2010-12-09 15:29:42 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2010-12-15 12:30:36 -0800
commit462e635e5b73ba9a4c03913b77138cd57ce4b050 (patch)
tree6ff0e84eecc6252d41d7c08730018c0149e7227f /fs/exec.c
parent0fcdcfbbc98f70f559e4b36773a69972489a6d8f (diff)
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.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/fs/exec.c b/fs/exec.c
index d68c378a313..c62efcb959c 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;