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authorTavis Ormandy <taviso@cmpxchg8b.com>2010-12-09 15:29:42 +0100
committerWilly Tarreau <w@1wt.eu>2011-02-09 22:15:39 +0100
commit041f1a0d35e62f447e007f665e437a59e5945e77 (patch)
tree93818d83cd2f624a64b6f9e0d8c42da87467b07b
parentab42f1f2ba5bea8d266ed383438ad5652617b366 (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.c5
-rw-r--r--mm/mmap.c16
2 files changed, 17 insertions, 4 deletions
diff --git a/fs/exec.c b/fs/exec.c
index fc30de0d1215..12e7ad2491b2 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 17d640d33df8..707ce0f74e6e 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);