From e9e5e3fae8da7e237049e00e0bfc9e32fd808fe8 Mon Sep 17 00:00:00 2001 From: Vegard Nossum Date: Mon, 22 Aug 2016 12:47:43 +0200 Subject: [PATCH] bdev: fix NULL pointer dereference I got this: kasan: GPF could be caused by NULL-ptr deref or user memory access general protection fault: 0000 [#1] PREEMPT SMP KASAN Dumping ftrace buffer: (ftrace buffer empty) CPU: 0 PID: 5505 Comm: syz-executor Not tainted 4.8.0-rc2+ #161 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.9.3-0-ge2fc41e-prebuilt.qemu-project.org 04/01/2014 task: ffff880113415940 task.stack: ffff880118350000 RIP: 0010:[] [] bd_mount+0x52/0xa0 RSP: 0018:ffff880118357ca0 EFLAGS: 00010207 RAX: dffffc0000000000 RBX: ffffffffffffffff RCX: ffffc90000bb6000 RDX: 0000000000000018 RSI: ffffffff846d6b20 RDI: 00000000000000c7 RBP: ffff880118357cb0 R08: ffff880115967c68 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801188211e8 R13: ffffffff847baa20 R14: ffff8801139cb000 R15: 0000000000000080 FS: 00007fa3ff6c0700(0000) GS:ffff88011aa00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fc1d8cc7e78 CR3: 0000000109f20000 CR4: 00000000000006f0 DR0: 000000000000001e DR1: 000000000000001e DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600 Stack: ffff880112cfd6c0 ffff8801188211e8 ffff880118357cf0 ffffffff8167f207 ffffffff816d7a1e ffff880112a413c0 ffffffff847baa20 ffff8801188211e8 0000000000000080 ffff880112cfd6c0 ffff880118357d38 ffffffff816dce0a Call Trace: [] mount_fs+0x97/0x2e0 [] ? alloc_vfsmnt+0x55e/0x760 [] vfs_kern_mount+0x7a/0x300 [] ? _raw_read_unlock+0x2c/0x50 [] do_mount+0x3d7/0x2730 [] ? trace_do_page_fault+0x1f4/0x3a0 [] ? copy_mount_string+0x40/0x40 [] ? memset+0x31/0x40 [] ? copy_mount_options+0x1ee/0x320 [] SyS_mount+0xb2/0x120 [] ? copy_mnt_ns+0x970/0x970 [] do_syscall_64+0x1c4/0x4e0 [] entry_SYSCALL64_slow_path+0x25/0x25 Code: 83 e8 63 1b fc ff 48 85 c0 48 89 c3 74 4c e8 56 35 d1 ff 48 8d bb c8 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 75 36 4c 8b a3 c8 00 00 00 48 b8 00 00 00 00 00 fc RIP [] bd_mount+0x52/0xa0 RSP ---[ end trace 13690ad962168b98 ]--- mount_pseudo() returns ERR_PTR(), not NULL, on error. Fixes: 3684aa7099e0 ("block-dev: enable writeback cgroup support") Cc: Shaohua Li Cc: Tejun Heo Cc: Jens Axboe Cc: stable@vger.kernel.org Signed-off-by: Vegard Nossum Signed-off-by: Jens Axboe --- fs/block_dev.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/block_dev.c b/fs/block_dev.c index c3cdde87cc8c..e17bdbdfe9b1 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -646,7 +646,7 @@ static struct dentry *bd_mount(struct file_system_type *fs_type, { struct dentry *dent; dent = mount_pseudo(fs_type, "bdev:", &bdev_sops, NULL, BDEVFS_MAGIC); - if (dent) + if (!IS_ERR(dent)) dent->d_sb->s_iflags |= SB_I_CGROUPWB; return dent; }