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:
__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
Analysis provided by Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
v2: Remove now redundant initialization in hugetlbfs_get_root
Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
---
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 54de77e..cf3669d 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;
}
--
2.7.4
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