Commit 4742a35d authored by Mike Kravetz's avatar Mike Kravetz Committed by Linus Torvalds
Browse files

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
    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

Analysis provided by Tetsuo Handa <>


Signed-off-by: default avatarMike Kravetz <>
Reported-by: default avatarDmitry Vyukov <>
Acked-by: default avatarHillf Danton <>
Cc: Tetsuo Handa <>
Cc: Michal Hocko <>
Cc: Dave Hansen <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 906f2a51
......@@ -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);
......@@ -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) {
init_special_inode(inode, mode, dev);
......@@ -937,6 +924,18 @@ static struct inode *hugetlbfs_alloc_inode(struct super_block *sb)
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;
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