security, hugetlbfs: write to user memory in hugetlbfs_destroy_inode

4 messages, 3 authors, 2017-03-23 · open the first message on its own page

security, hugetlbfs: write to user memory in hugetlbfs_destroy_inode

From: Dmitry Vyukov <dvyukov@google.com>
Date: 2017-03-23 13:07:23

Hello,

I've got the following report while running syzkaller fuzzer on
093b995e3b55a0ae0670226ddfcb05bfbf0099ae. Note the preceding injected
kmalloc failure in inode_alloc_security, most likely it's the root
cause.


FAULT_INJECTION: forcing a failure.
name failslab, interval 1, probability 0, space 0, times 0
CPU: 3 PID: 14086 Comm: syz-executor6 Not tainted 4.11.0-rc3+ #364
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:16 [inline]
 dump_stack+0x1b8/0x28d lib/dump_stack.c:52
 fail_dump lib/fault-inject.c:45 [inline]
 should_fail+0x78a/0x870 lib/fault-inject.c:154
 should_failslab+0xec/0x120 mm/failslab.c:31
 slab_pre_alloc_hook mm/slab.h:434 [inline]
 slab_alloc mm/slab.c:3394 [inline]
 kmem_cache_alloc+0x200/0x720 mm/slab.c:3570
 kmem_cache_zalloc include/linux/slab.h:653 [inline]
 inode_alloc_security security/selinux/hooks.c:221 [inline]
 selinux_inode_alloc_security+0xf9/0x390 security/selinux/hooks.c:2833
 security_inode_alloc+0x90/0xd0 security/security.c:387
 inode_init_always+0x5af/0xc20 fs/inode.c:166
 alloc_inode+0x82/0x180 fs/inode.c:214
 new_inode_pseudo+0x69/0x190 fs/inode.c:889
 new_inode+0x1c/0x40 fs/inode.c:918
 hugetlbfs_get_inode+0x40/0x420 fs/hugetlbfs/inode.c:734
 hugetlb_file_setup+0x329/0x9f0 fs/hugetlbfs/inode.c:1282
 newseg+0x422/0xd30 ipc/shm.c:575
 ipcget_new ipc/util.c:285 [inline]
 ipcget+0x21e/0x580 ipc/util.c:639
 SYSC_shmget ipc/shm.c:673 [inline]
 SyS_shmget+0x158/0x230 ipc/shm.c:657
 entry_SYSCALL_64_fastpath+0x1f/0xc2
RIP: 0033:0x445b79
RSP: 002b:00007f9dcc5df858 EFLAGS: 00000282 ORIG_RAX: 000000000000001d
RAX: ffffffffffffffda RBX: 0000000000708000 RCX: 0000000000445b79

52 more lines

Re: security, hugetlbfs: write to user memory in hugetlbfs_destroy_inode

From: Dmitry Vyukov <dvyukov@google.com>
Date: 2017-03-23 13:09:45

On Thu, Mar 23, 2017 at 2:06 PM, Dmitry Vyukov [off-list ref] wrote:

Hello,

I've got the following report while running syzkaller fuzzer on
093b995e3b55a0ae0670226ddfcb05bfbf0099ae. Note the preceding injected
kmalloc failure in inode_alloc_security, most likely it's the root
cause.


FAULT_INJECTION: forcing a failure.
name failslab, interval 1, probability 0, space 0, times 0
CPU: 3 PID: 14086 Comm: syz-executor6 Not tainted 4.11.0-rc3+ #364
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:16 [inline]
 dump_stack+0x1b8/0x28d lib/dump_stack.c:52
 fail_dump lib/fault-inject.c:45 [inline]
 should_fail+0x78a/0x870 lib/fault-inject.c:154
 should_failslab+0xec/0x120 mm/failslab.c:31
 slab_pre_alloc_hook mm/slab.h:434 [inline]
 slab_alloc mm/slab.c:3394 [inline]
 kmem_cache_alloc+0x200/0x720 mm/slab.c:3570
 kmem_cache_zalloc include/linux/slab.h:653 [inline]
 inode_alloc_security security/selinux/hooks.c:221 [inline]
 selinux_inode_alloc_security+0xf9/0x390 security/selinux/hooks.c:2833
 security_inode_alloc+0x90/0xd0 security/security.c:387
 inode_init_always+0x5af/0xc20 fs/inode.c:166
 alloc_inode+0x82/0x180 fs/inode.c:214
 new_inode_pseudo+0x69/0x190 fs/inode.c:889
 new_inode+0x1c/0x40 fs/inode.c:918
 hugetlbfs_get_inode+0x40/0x420 fs/hugetlbfs/inode.c:734
 hugetlb_file_setup+0x329/0x9f0 fs/hugetlbfs/inode.c:1282
 newseg+0x422/0xd30 ipc/shm.c:575
 ipcget_new ipc/util.c:285 [inline]
 ipcget+0x21e/0x580 ipc/util.c:639
 SYSC_shmget ipc/shm.c:673 [inline]
 SyS_shmget+0x158/0x230 ipc/shm.c:657
 entry_SYSCALL_64_fastpath+0x1f/0xc2
RIP: 0033:0x445b79
RSP: 002b:00007f9dcc5df858 EFLAGS: 00000282 ORIG_RAX: 000000000000001d
RAX: ffffffffffffffda RBX: 0000000000708000 RCX: 0000000000445b79

48 more quoted lines


Similar on address 0x2d302e31312e35c7, looks like uninit.

==================================================================
BUG: KASAN: wild-memory-access in atomic_inc
include/asm-generic/atomic-instrumented.h:87 [inline] at addr
2d302e31312e35c7
BUG: KASAN: wild-memory-access in __lock_acquire+0x21a/0x3a80
kernel/locking/lockdep.c:3239 at addr 2d302e31312e35c7
Write of size 4 by task syz-executor1/9446
CPU: 1 PID: 9446 Comm: syz-executor1 Not tainted 4.11.0-rc3+ #364
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:16 [inline]
 dump_stack+0x1b8/0x28d lib/dump_stack.c:52
 kasan_report_error mm/kasan/report.c:291 [inline]
 kasan_report.part.2+0x34a/0x480 mm/kasan/report.c:316
 kasan_report+0x21/0x30 mm/kasan/report.c:303
 check_memory_region_inline mm/kasan/kasan.c:326 [inline]
 check_memory_region+0x137/0x190 mm/kasan/kasan.c:333
 kasan_check_write+0x14/0x20 mm/kasan/kasan.c:344
 atomic_inc include/asm-generic/atomic-instrumented.h:87 [inline]
 __lock_acquire+0x21a/0x3a80 kernel/locking/lockdep.c:3239
 lock_acquire+0x1ee/0x590 kernel/locking/lockdep.c:3762
 __raw_write_lock include/linux/rwlock_api_smp.h:210 [inline]
 _raw_write_lock+0x33/0x50 kernel/locking/spinlock.c:295
 mpol_free_shared_policy+0x43/0xb0 mm/mempolicy.c:2536
 hugetlbfs_destroy_inode+0xca/0x120 fs/hugetlbfs/inode.c:952
 alloc_inode+0x10d/0x180 fs/inode.c:216
 new_inode_pseudo+0x69/0x190 fs/inode.c:889
 new_inode+0x1c/0x40 fs/inode.c:918
 hugetlbfs_get_inode+0x40/0x420 fs/hugetlbfs/inode.c:734
 hugetlb_file_setup+0x329/0x9f0 fs/hugetlbfs/inode.c:1282
 newseg+0x422/0xd30 ipc/shm.c:575
 ipcget_new ipc/util.c:285 [inline]
 ipcget+0x21e/0x580 ipc/util.c:639
 SYSC_shmget ipc/shm.c:673 [inline]
 SyS_shmget+0x158/0x230 ipc/shm.c:657
 entry_SYSCALL_64_fastpath+0x1f/0xc2

12 more lines

Re: security, hugetlbfs: write to user memory in hugetlbfs_destroy_inode

From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Date: 2017-03-23 13:49:45

Dmitry Vyukov wrote:

On Thu, Mar 23, 2017 at 2:06 PM, Dmitry Vyukov [off-list ref] wrote:

quoted

Hello,

I've got the following report while running syzkaller fuzzer on
093b995e3b55a0ae0670226ddfcb05bfbf0099ae. Note the preceding injected
kmalloc failure in inode_alloc_security, most likely it's the root
cause.

I don't think inode_alloc_security() failure is the root cause.
I think this is a bug in hugetlbfs or mm part.

If inode_alloc_security() fails, inode->i_security remains NULL
which was initialized to NULL at security_inode_alloc(). Thus,
security_inode_alloc() is irrelevant to this problem.

inode_init_always() returned -ENOMEM due to fault injection and

	if (unlikely(inode_init_always(sb, inode))) {
		if (inode->i_sb->s_op->destroy_inode)
			inode->i_sb->s_op->destroy_inode(inode);
		else
			kmem_cache_free(inode_cachep, inode);
		return NULL;
	}

hugetlbfs_destroy_inode() was called via inode->i_sb->s_op->destroy_inode()
when inode initialization failed

static void hugetlbfs_destroy_inode(struct inode *inode)
{
	hugetlbfs_inc_free_inodes(HUGETLBFS_SB(inode->i_sb));
	mpol_free_shared_policy(&HUGETLBFS_I(inode)->policy);
	call_rcu(&inode->i_rcu, hugetlbfs_i_callback);
}

but mpol_shared_policy_init() is called only when new_inode() succeeds.

	inode = new_inode(sb);
	if (inode) {
(...snipped...)
		info = HUGETLBFS_I(inode);
		/*
		 * The policy is initialized here even if we are creating a
		 * private inode because initialization simply creates an
		 * an empty rb tree and calls rwlock_init(), later when we
		 * call mpol_free_shared_policy() it will just return because
		 * the rb tree will still be empty.

6 more lines

Re: security, hugetlbfs: write to user memory in hugetlbfs_destroy_inode

From: Mike Kravetz <hidden>
Date: 2017-03-23 20:35:00

On 03/23/2017 06:49 AM, Tetsuo Handa wrote:

Dmitry Vyukov wrote:

quoted

On Thu, Mar 23, 2017 at 2:06 PM, Dmitry Vyukov [off-list ref] wrote:

quoted

Hello,

I've got the following report while running syzkaller fuzzer on
093b995e3b55a0ae0670226ddfcb05bfbf0099ae. Note the preceding injected
kmalloc failure in inode_alloc_security, most likely it's the root
cause.

I don't think inode_alloc_security() failure is the root cause.
I think this is a bug in hugetlbfs or mm part.

If inode_alloc_security() fails, inode->i_security remains NULL
which was initialized to NULL at security_inode_alloc(). Thus,
security_inode_alloc() is irrelevant to this problem.

inode_init_always() returned -ENOMEM due to fault injection and

	if (unlikely(inode_init_always(sb, inode))) {
		if (inode->i_sb->s_op->destroy_inode)
			inode->i_sb->s_op->destroy_inode(inode);
		else
			kmem_cache_free(inode_cachep, inode);
		return NULL;
	}

hugetlbfs_destroy_inode() was called via inode->i_sb->s_op->destroy_inode()
when inode initialization failed

static void hugetlbfs_destroy_inode(struct inode *inode)
{
	hugetlbfs_inc_free_inodes(HUGETLBFS_SB(inode->i_sb));
	mpol_free_shared_policy(&HUGETLBFS_I(inode)->policy);
	call_rcu(&inode->i_rcu, hugetlbfs_i_callback);
}

but mpol_shared_policy_init() is called only when new_inode() succeeds.

	inode = new_inode(sb);
	if (inode) {

11 more quoted lines

Thank you for analysis (and Dmitry for reporting).

This certainly does look like a hugetlbfs bug.  I will put together a
patch to fix.

-- 
Mike Kravetz
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