• Chao Yu's avatar
    ecryptfs: avoid to access NULL pointer when write metadata in xattr · f52c88e8
    Chao Yu authored
    commit 35425ea2492175fd39f6116481fe98b2b3ddd4ca upstream.
    
    Christopher Head 2014-06-28 05:26:20 UTC described:
    "I tried to reproduce this on 3.12.21. Instead, when I do "echo hello > foo"
    in an ecryptfs mount with ecryptfs_xattr specified, I get a kernel crash:
    
    BUG: unable to handle kernel NULL pointer dereference at           (null)
    IP: [<ffffffff8110eb39>] fsstack_copy_attr_all+0x2/0x61
    PGD d7840067 PUD b2c3c067 PMD 0
    Oops: 0002 [#1] SMP
    Modules linked in: nvidia(PO)
    CPU: 3 PID: 3566 Comm: bash Tainted: P           O 3.12.21-gentoo-r1 #2
    Hardware name: ASUSTek Computer Inc. G60JX/G60JX, BIOS 206 03/15/2010
    task: ffff8801948944c0 ti: ffff8800bad70000 task.ti: ffff8800bad70000
    RIP: 0010:[<ffffffff8110eb39>]  [<ffffffff8110eb39>] fsstack_copy_attr_all+0x2/0x61
    RSP: 0018:ffff8800bad71c10  EFLAGS: 00010246
    RAX: 00000000000181a4 RBX: ffff880198648480 RCX: 0000000000000000
    RDX: 0000000000000004 RSI: ffff880172010450 RDI: 0000000000000000
    RBP: ffff880198490e40 R08: 0000000000000000 R09: 0000000000000000
    R10: ffff880172010450 R11: ffffea0002c51e80 R12: 0000000000002000
    R13: 000000000000001a R14: 0000000000000000 R15: ffff880198490e40
    FS:  00007ff224caa700(0000) GS:ffff88019fcc0000(0000) knlGS:0000000000000000
    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 0000000000000000 CR3: 00000000bb07f000 CR4: 00000000000007e0
    Stack:
    ffffffff811826e8 ffff8800a39d8000 0000000000000000 000000000000001a
    ffff8800a01d0000 ffff8800a39d8000 ffffffff81185fd5 ffffffff81082c2c
    00000001a39d8000 53d0abbc98490e40 0000000000000037 ffff8800a39d8220
    Call Trace:
    [<ffffffff811826e8>] ? ecryptfs_setxattr+0x40/0x52
    [<ffffffff81185fd5>] ? ecryptfs_write_metadata+0x1b3/0x223
    [<ffffffff81082c2c>] ? should_resched+0x5/0x23
    [<ffffffff8118322b>] ? ecryptfs_initialize_file+0xaf/0xd4
    [<ffffffff81183344>] ? ecryptfs_create+0xf4/0x142
    [<ffffffff810f8c0d>] ? vfs_create+0x48/0x71
    [<ffffffff810f9c86>] ? do_last.isra.68+0x559/0x952
    [<ffffffff810f7ce7>] ? link_path_walk+0xbd/0x458
    [<ffffffff810fa2a3>] ? path_openat+0x224/0x472
    [<ffffffff810fa7bd>] ? do_filp_open+0x2b/0x6f
    [<ffffffff81103606>] ? __alloc_fd+0xd6/0xe7
    [<ffffffff810ee6ab>] ? do_sys_open+0x65/0xe9
    [<ffffffff8157d022>] ? system_call_fastpath+0x16/0x1b
    RIP  [<ffffffff8110eb39>] fsstack_copy_attr_all+0x2/0x61
    RSP <ffff8800bad71c10>
    CR2: 0000000000000000
    ---[ end trace df9dba5f1ddb8565 ]---"
    
    If we create a file when we mount with ecryptfs_xattr_metadata option, we will
    encounter a crash in this path:
    ->ecryptfs_create
      ->ecryptfs_initialize_file
        ->ecryptfs_write_metadata
          ->ecryptfs_write_metadata_to_xattr
            ->ecryptfs_setxattr
              ->fsstack_copy_attr_all
    It's because our dentry->d_inode used in fsstack_copy_attr_all is NULL, and it
    will be initialized when ecryptfs_initialize_file finish.
    
    So we should skip copying attr from lower inode when the value of ->d_inode is
    invalid.
    Signed-off-by: default avatarChao Yu <chao2.yu@samsung.com>
    Signed-off-by: default avatarTyler Hicks <tyhicks@canonical.com>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    f52c88e8
inode.c 32.8 KB