From 4742a35d9de745e867405b4311e1aac412f0ace1 Mon Sep 17 00:00:00 2001 From: Mike Kravetz Date: Fri, 31 Mar 2017 15:12:01 -0700 Subject: [PATCH] hugetlbfs: initialize shared policy as part of inode allocation Any time after inode allocation, destroy_inode can be called. The hugetlbfs inode contains a shared_policy structure, and mpol_free_shared_policy is unconditionally called as part of hugetlbfs_destroy_inode. Initialize the policy as part of inode allocation so that any quick (error path) calls to destroy_inode will be handed an initialized policy. syzkaller fuzzer found this bug, that resulted in the following: BUG: KASAN: user-memory-access in atomic_inc include/asm-generic/atomic-instrumented.h:87 [inline] at addr 000000131730bd7a BUG: KASAN: user-memory-access in __lock_acquire+0x21a/0x3a80 kernel/locking/lockdep.c:3239 at addr 000000131730bd7a Write of size 4 by task syz-executor6/14086 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: 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 Analysis provided by Tetsuo Handa Link: http://lkml.kernel.org/r/1490477850-7944-1-git-send-email-mike.kravetz@oracle.com Signed-off-by: Mike Kravetz Reported-by: Dmitry Vyukov Acked-by: Hillf Danton Cc: Tetsuo Handa Cc: Michal Hocko Cc: Dave Hansen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/hugetlbfs/inode.c | 25 ++++++++++++------------- 1 file changed, 12 insertions(+), 13 deletions(-) diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index 8f96461236f6..7163fe014b57 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -695,14 +695,11 @@ static struct inode *hugetlbfs_get_root(struct super_block *sb, inode = new_inode(sb); if (inode) { - struct hugetlbfs_inode_info *info; inode->i_ino = get_next_ino(); inode->i_mode = S_IFDIR | config->mode; inode->i_uid = config->uid; inode->i_gid = config->gid; inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode); - info = HUGETLBFS_I(inode); - mpol_shared_policy_init(&info->policy, NULL); inode->i_op = &hugetlbfs_dir_inode_operations; inode->i_fop = &simple_dir_operations; /* directory inodes start off with i_nlink == 2 (for "." entry) */ @@ -733,7 +730,6 @@ static struct inode *hugetlbfs_get_inode(struct super_block *sb, inode = new_inode(sb); if (inode) { - struct hugetlbfs_inode_info *info; inode->i_ino = get_next_ino(); inode_init_owner(inode, dir, mode); lockdep_set_class(&inode->i_mapping->i_mmap_rwsem, @@ -741,15 +737,6 @@ static struct inode *hugetlbfs_get_inode(struct super_block *sb, inode->i_mapping->a_ops = &hugetlbfs_aops; inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode); inode->i_mapping->private_data = resv_map; - 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. - */ - mpol_shared_policy_init(&info->policy, NULL); switch (mode & S_IFMT) { default: init_special_inode(inode, mode, dev); @@ -937,6 +924,18 @@ static struct inode *hugetlbfs_alloc_inode(struct super_block *sb) hugetlbfs_inc_free_inodes(sbinfo); return NULL; } + + /* + * Any time after allocation, hugetlbfs_destroy_inode can be called + * for the inode. mpol_free_shared_policy is unconditionally called + * as part of hugetlbfs_destroy_inode. So, initialize policy here + * in case of a quick call to destroy. + * + * Note that the policy is initialized even if we are creating a + * private inode. This simplifies hugetlbfs_destroy_inode. + */ + mpol_shared_policy_init(&p->policy, NULL); + return &p->vfs_inode; }