linux.git/fs/ext2/inode.c, branch v4.8

ext2: fix filesystem deadlock while reading corrupted xattr block

2016-07-06T02:02:41+00:00

This bug can be reproducible with fsfuzzer, although, I couldn't reproduce it
100% of my tries, it is quite easily reproducible.

During the deletion of an inode, ext2_xattr_delete_inode() does not check if the
block pointed by EXT2_I(inode)->i_file_acl is a valid data block, this might
lead to a deadlock, when i_file_acl == 1, and the filesystem block size is 1024.

In that situation, ext2_xattr_delete_inode, will load the superblock's buffer
head (instead of a valid i_file_acl block), and then lock that buffer head,
which, ext2_sync_super will also try to lock, making the filesystem deadlock in
the following stack trace:

root     17180  0.0  0.0 113660   660 pts/0    D+   07:08   0:00 rmdir
/media/test/dir1

[] __sync_dirty_buffer+0xaf/0x100
[] sync_dirty_buffer+0x13/0x20
[] ext2_sync_super+0xb7/0xc0 [ext2]
[] ext2_error+0x119/0x130 [ext2]
[] ext2_free_blocks+0x83/0x350 [ext2]
[] ext2_xattr_delete_inode+0x173/0x190 [ext2]
[] ext2_evict_inode+0xc9/0x130 [ext2]
[] evict+0xb3/0x180
[] iput+0x1b8/0x240
[] d_delete+0x11c/0x150
[] vfs_rmdir+0xfe/0x120
[] do_rmdir+0x17e/0x1f0
[] SyS_rmdir+0x16/0x20
[] entry_SYSCALL_64_fastpath+0x1a/0xa4
[] 0xffffffffffffffff

Fix this by using the same approach ext4 uses to test data blocks validity,
implementing ext2_data_block_valid.

An another possibility when the superblock is very corrupted, is that i_file_acl
is 1, block_count is 1 and first_data_block is 0. For such situations, we might
have i_file_acl pointing to a 'valid' block, but still step over the superblock.
The approach I used was to also test if the superblock is not in the range
described by ext2_data_block_valid() arguments

Signed-off-by: Carlos Maiolino 
Signed-off-by: Theodore Ts'o

Merge tag 'dax-misc-for-4.7' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm

2016-05-27T02:34:26+00:00

Pull misc DAX updates from Vishal Verma:
 "DAX error handling for 4.7

   - Until now, dax has been disabled if media errors were found on any
     device.  This enables the use of DAX in the presence of these
     errors by making all sector-aligned zeroing go through the driver.

   - The driver (already) has the ability to clear errors on writes that
     are sent through the block layer using 'DSMs' defined in ACPI 6.1.

  Other misc changes:

   - When mounting DAX filesystems, check to make sure the partition is
     page aligned.  This is a requirement for DAX, and previously, we
     allowed such unaligned mounts to succeed, but subsequent
     reads/writes would fail.

   - Misc/cleanup fixes from Jan that remove unused code from DAX
     related to zeroing, writeback, and some size checks"

* tag 'dax-misc-for-4.7' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm:
  dax: fix a comment in dax_zero_page_range and dax_truncate_page
  dax: for truncate/hole-punch, do zeroing through the driver if possible
  dax: export a low-level __dax_zero_page_range helper
  dax: use sb_issue_zerout instead of calling dax_clear_sectors
  dax: enable dax in the presence of known media errors (badblocks)
  dax: fallback from pmd to pte on error
  block: Update blkdev_dax_capable() for consistency
  xfs: Add alignment check for DAX mount
  ext2: Add alignment check for DAX mount
  ext4: Add alignment check for DAX mount
  block: Add bdev_dax_supported() for dax mount checks
  block: Add vfs_msg() interface
  dax: Remove redundant inode size checks
  dax: Remove pointless writeback from dax_do_io()
  dax: Remove zeroing from dax_io()
  dax: Remove dead zeroing code from fault handlers
  ext2: Avoid DAX zeroing to corrupt data
  ext2: Fix block zeroing in ext2_get_blocks() for DAX
  dax: Remove complete_unwritten argument
  DAX: move RADIX_DAX_ definitions to dax.c

dax: use sb_issue_zerout instead of calling dax_clear_sectors

2016-05-18T18:16:56+00:00

dax_clear_sectors() cannot handle poisoned blocks.  These must be
zeroed using the BIO interface instead.  Convert ext2 and XFS to use
only sb_issue_zerout().

Reviewed-by: Jeff Moyer 
Reviewed-by: Christoph Hellwig 
Reviewed-by: Jan Kara 
Signed-off-by: Matthew Wilcox 
[vishal: Also remove the dax_clear_sectors function entirely]
Signed-off-by: Vishal Verma

ext2: Avoid DAX zeroing to corrupt data

2016-05-17T06:44:07+00:00

Currently ext2 zeroes any data blocks allocated for DAX inode however it
still returns them as BH_New. Thus DAX code zeroes them again in
dax_insert_mapping() which can possibly overwrite the data that has been
already stored to those blocks by a racing dax_io(). Avoid marking
pre-zeroed buffers as new.

Reviewed-by: Ross Zwisler 
Signed-off-by: Jan Kara 
Signed-off-by: Vishal Verma

ext2: Fix block zeroing in ext2_get_blocks() for DAX

2016-05-17T06:41:24+00:00

When zeroing allocated blocks for DAX, we accidentally zeroed only the
first allocated block instead of all of them. So far this problem is
hidden by the fact that page faults always need only a single block and
DAX write code zeroes blocks again. But the zeroing in DAX code is racy
and needs to be removed so fix the zeroing in ext2 to zero all allocated
blocks.

Reported-by: Ross Zwisler 
Signed-off-by: Jan Kara 
Signed-off-by: Vishal Verma

direct-io: eliminate the offset argument to ->direct_IO

2016-05-01T23:58:39+00:00

Including blkdev_direct_IO and dax_do_io.  It has to be ki_pos to actually
work, so eliminate the superflous argument.

Signed-off-by: Christoph Hellwig 
Signed-off-by: Al Viro

dax: move writeback calls into the filesystems

2016-02-27T18:28:52+00:00

Previously calls to dax_writeback_mapping_range() for all DAX filesystems
(ext2, ext4 & xfs) were centralized in filemap_write_and_wait_range().

dax_writeback_mapping_range() needs a struct block_device, and it used
to get that from inode->i_sb->s_bdev.  This is correct for normal inodes
mounted on ext2, ext4 and XFS filesystems, but is incorrect for DAX raw
block devices and for XFS real-time files.

Instead, call dax_writeback_mapping_range() directly from the filesystem
->writepages function so that it can supply us with a valid block
device.  This also fixes DAX code to properly flush caches in response
to sync(2).

Signed-off-by: Ross Zwisler 
Signed-off-by: Jan Kara 
Cc: Al Viro 
Cc: Dan Williams 
Cc: Dave Chinner 
Cc: Jens Axboe 
Cc: Matthew Wilcox 
Cc: Theodore Ts'o 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

dax: give DAX clearing code correct bdev

2016-02-27T18:28:52+00:00

dax_clear_blocks() needs a valid struct block_device and previously it
was using inode->i_sb->s_bdev in all cases.  This is correct for normal
inodes on mounted ext2, ext4 and XFS filesystems, but is incorrect for
DAX raw block devices and for XFS real-time devices.

Instead, rename dax_clear_blocks() to dax_clear_sectors(), and change
its arguments to take a bdev and a sector instead of an inode and a
block.  This better reflects what the function does, and it allows the
filesystem and raw block device code to pass in an appropriate struct
block_device.

Signed-off-by: Ross Zwisler 
Suggested-by: Dan Williams 
Reviewed-by: Jan Kara 
Cc: Theodore Ts'o 
Cc: Al Viro 
Cc: Dave Chinner 
Cc: Jens Axboe 
Cc: Matthew Wilcox 
Cc: Ross Zwisler 
Cc: Theodore Ts'o 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

ext2, ext4: only set S_DAX for regular inodes

2016-02-27T18:28:52+00:00

When S_DAX is set on an inode we assume that if there are pages attached
to the mapping (mapping->nrpages != 0), those pages are clean zero pages
that were used to service reads from holes.  Any dirty data associated
with the inode should be in the form of DAX exceptional entries
(mapping->nrexceptional) that is written back via
dax_writeback_mapping_range().

With the current code, though, this isn't always true.  For example,
ext2 and ext4 directory inodes can have S_DAX set, but have their dirty
data stored as dirty page cache entries.  For these types of inodes,
having S_DAX set doesn't really make sense since their I/O doesn't
actually happen through the DAX code path.

Instead, only allow S_DAX to be set for regular inodes for ext2 and
ext4.  This allows us to have strict DAX vs non-DAX paths in the
writeback code.

Signed-off-by: Ross Zwisler 
Reviewed-by: Jan Kara 
Cc: Theodore Ts'o 
Cc: Al Viro 
Cc: Dan Williams 
Cc: Dave Chinner 
Cc: Jens Axboe 
Cc: Matthew Wilcox 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

don't put symlink bodies in pagecache into highmem

2015-12-09T03:41:36+00:00

kmap() in page_follow_link_light() needed to go - allowing to hold
an arbitrary number of kmaps for long is a great way to deadlocking
the system.

new helper (inode_nohighmem(inode)) needs to be used for pagecache
symlinks inodes; done for all in-tree cases.  page_follow_link_light()
instrumented to yell about anything missed.

Signed-off-by: Al Viro