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    Subject[10/90] ext4: reject too-large filesystems on 32-bit kernels
    2.6.31-stable review patch.  If anyone has any objections, please let us know.

    ------------------
    (cherry picked from commit bf43d84b185e2ff54598f8c58a5a8e63148b6e90)

    ext4 will happily mount a > 16T filesystem on a 32-bit box, but
    this is not safe; writes to the block device will wrap past 16T
    and the page cache can't index past 16T (232 index * 4k pages).

    Adding another test to the existing "too many sectors" test
    should do the trick.

    Add a comment, a relevant return value, and fix the reference
    to the CONFIG_LBD(AF) option as well.

    Signed-off-by: Eric Sandeen <sandeen@redhat.com>
    Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
    ---
    fs/ext4/super.c | 13 ++++++++++---
    1 file changed, 10 insertions(+), 3 deletions(-)

    --- a/fs/ext4/super.c
    +++ b/fs/ext4/super.c
    @@ -2550,12 +2550,19 @@ static int ext4_fill_super(struct super_
    goto failed_mount;
    }

    - if (ext4_blocks_count(es) >
    - (sector_t)(~0ULL) >> (sb->s_blocksize_bits - 9)) {
    + /*
    + * Test whether we have more sectors than will fit in sector_t,
    + * and whether the max offset is addressable by the page cache.
    + */
    + if ((ext4_blocks_count(es) >
    + (sector_t)(~0ULL) >> (sb->s_blocksize_bits - 9)) ||
    + (ext4_blocks_count(es) >
    + (pgoff_t)(~0ULL) >> (PAGE_CACHE_SHIFT - sb->s_blocksize_bits))) {
    ext4_msg(sb, KERN_ERR, "filesystem"
    - " too large to mount safely");
    + " too large to mount safely on this system");
    if (sizeof(sector_t) < 8)
    ext4_msg(sb, KERN_WARNING, "CONFIG_LBDAF not enabled");
    + ret = -EFBIG;
    goto failed_mount;
    }




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