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ext4: check bh in ext4_read_block_bitmap()

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commit 15b49132fc upstream.

Validate the bh pointer before using it, since
ext4_read_block_bitmap_nowait() might return NULL.

I've seen this in fsfuzz testing.

 EXT4-fs error (device loop0): ext4_read_block_bitmap_nowait:385: comm touch: Cannot get buffer for block bitmap - block_group = 0, block_bitmap = 3925999616
 BUG: unable to handle kernel NULL pointer dereference at           (null)
 IP: [<ffffffff8121de25>] ext4_wait_block_bitmap+0x25/0xe0
 ...
 Call Trace:
  [<ffffffff8121e1e5>] ext4_read_block_bitmap+0x35/0x60
  [<ffffffff8125e9c6>] ext4_free_blocks+0x236/0xb80
  [<ffffffff811d0d36>] ? __getblk+0x36/0x70
  [<ffffffff811d0a5f>] ? __find_get_block+0x8f/0x210
  [<ffffffff81191ef3>] ? kmem_cache_free+0x33/0x140
  [<ffffffff812678e5>] ext4_xattr_release_block+0x1b5/0x1d0
  [<ffffffff812679be>] ext4_xattr_delete_inode+0xbe/0x100
  [<ffffffff81222a7c>] ext4_free_inode+0x7c/0x4d0
  [<ffffffff812277b8>] ? ext4_mark_inode_dirty+0x88/0x230
  [<ffffffff8122993c>] ext4_evict_inode+0x32c/0x490
  [<ffffffff811b8cd7>] evict+0xa7/0x1c0
  [<ffffffff811b8ed3>] iput_final+0xe3/0x170
  [<ffffffff811b8f9e>] iput+0x3e/0x50
  [<ffffffff812316fd>] ext4_add_nondir+0x4d/0x90
  [<ffffffff81231d0b>] ext4_create+0xeb/0x170
  [<ffffffff811aae9c>] vfs_create+0xac/0xd0
  [<ffffffff811ac845>] lookup_open+0x185/0x1c0
  [<ffffffff8129e3b9>] ? selinux_inode_permission+0xa9/0x170
  [<ffffffff811acb54>] do_last+0x2d4/0x7a0
  [<ffffffff811af743>] path_openat+0xb3/0x480
  [<ffffffff8116a8a1>] ? handle_mm_fault+0x251/0x3b0
  [<ffffffff811afc49>] do_filp_open+0x49/0xa0
  [<ffffffff811bbaad>] ? __alloc_fd+0xdd/0x150
  [<ffffffff8119da28>] do_sys_open+0x108/0x1f0
  [<ffffffff8119db51>] sys_open+0x21/0x30
  [<ffffffff81618959>] system_call_fastpath+0x16/0x1b

Also fix comment for ext4_read_block_bitmap_nowait()

Signed-off-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Eryu Guan 2013-01-12 16:33:25 -05:00 committed by Greg Kroah-Hartman
parent f74e995c9b
commit ced2decfe3
1 changed files with 3 additions and 1 deletions
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4
fs/ext4/balloc.c
View file

@ -326,7 +326,7 @@ err_out:
return 0;
}
/**
* ext4_read_block_bitmap()
* ext4_read_block_bitmap_nowait()
* @sb: super block
* @block_group: given block group
*
@ -422,6 +422,8 @@ ext4_read_block_bitmap(struct super_block *sb, ext4_group_t block_group)
struct buffer_head *bh;
bh = ext4_read_block_bitmap_nowait(sb, block_group);
if (!bh)
return NULL;
if (ext4_wait_block_bitmap(sb, block_group, bh)) {
put_bh(bh);
return NULL;