lkml.org 
[lkml]   [2018]   [Apr]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 4.16 001/113] ext4: prevent right-shifting extents beyond EXT_MAX_BLOCKS
    Date
    4.16-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Eric Biggers <ebiggers@google.com>

    commit 349fa7d6e1935f49bf4161c4900711b2989180a9 upstream.

    During the "insert range" fallocate operation, extents starting at the
    range offset are shifted "right" (to a higher file offset) by the range
    length. But, as shown by syzbot, it's not validated that this doesn't
    cause extents to be shifted beyond EXT_MAX_BLOCKS. In that case
    ->ee_block can wrap around, corrupting the extent tree.

    Fix it by returning an error if the space between the end of the last
    extent and EXT4_MAX_BLOCKS is smaller than the range being inserted.

    This bug can be reproduced by running the following commands when the
    current directory is on an ext4 filesystem with a 4k block size:

    fallocate -l 8192 file
    fallocate --keep-size -o 0xfffffffe000 -l 4096 -n file
    fallocate --insert-range -l 8192 file

    Then after unmounting the filesystem, e2fsck reports corruption.

    Reported-by: syzbot+06c885be0edcdaeab40c@syzkaller.appspotmail.com
    Fixes: 331573febb6a ("ext4: Add support FALLOC_FL_INSERT_RANGE for fallocate")
    Cc: stable@vger.kernel.org # v4.2+
    Signed-off-by: Eric Biggers <ebiggers@google.com>
    Signed-off-by: Theodore Ts'o <tytso@mit.edu>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/ext4/extents.c | 16 +++++++++++-----
    1 file changed, 11 insertions(+), 5 deletions(-)

    --- a/fs/ext4/extents.c
    +++ b/fs/ext4/extents.c
    @@ -5334,8 +5334,9 @@ ext4_ext_shift_extents(struct inode *ino
    stop = le32_to_cpu(extent->ee_block);

    /*
    - * In case of left shift, Don't start shifting extents until we make
    - * sure the hole is big enough to accommodate the shift.
    + * For left shifts, make sure the hole on the left is big enough to
    + * accommodate the shift. For right shifts, make sure the last extent
    + * won't be shifted beyond EXT_MAX_BLOCKS.
    */
    if (SHIFT == SHIFT_LEFT) {
    path = ext4_find_extent(inode, start - 1, &path,
    @@ -5355,9 +5356,14 @@ ext4_ext_shift_extents(struct inode *ino

    if ((start == ex_start && shift > ex_start) ||
    (shift > start - ex_end)) {
    - ext4_ext_drop_refs(path);
    - kfree(path);
    - return -EINVAL;
    + ret = -EINVAL;
    + goto out;
    + }
    + } else {
    + if (shift > EXT_MAX_BLOCKS -
    + (stop + ext4_ext_get_actual_len(extent))) {
    + ret = -EINVAL;
    + goto out;
    }
    }


    \
     
     \ /
      Last update: 2018-04-30 21:57    [W:4.269 / U:0.004 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site