• Ming Lei's avatar
    block: add bio_truncate to fix guard_bio_eod · 85a8ce62
    Ming Lei authored
    Some filesystem, such as vfat, may send bio which crosses device boundary,
    and the worse thing is that the IO request starting within device boundaries
    can contain more than one segment past EOD.
    
    Commit dce30ca9 ("fs: fix guard_bio_eod to check for real EOD errors")
    tries to fix this issue by returning -EIO for this situation. However,
    this way lets fs user code lose chance to handle -EIO, then sync_inodes_sb()
    may hang for ever.
    
    Also the current truncating on last segment is dangerous by updating the
    last bvec, given bvec table becomes not immutable any more, and fs bio
    users may not retrieve the truncated pages via bio_for_each_segment_all() in
    its .end_io callback.
    
    Fixes this issue by supporting multi-segment truncating. And the
    approach is simpler:
    
    - just update bio size since block layer can make correct bvec with
    the updated bio size. Then bvec table becomes really immutable.
    
    - zero all truncated segments for read bio
    
    Cc: Carlos Maiolino <cmaiolino@redhat.com>
    Cc: linux-fsdevel@vger.kernel.org
    Fixed-by: dce30ca9 ("fs: fix guard_bio_eod to check for real EOD errors")
    Reported-by: syzbot+2b9e54155c8c25d8d165@syzkaller.appspotmail.com
    Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
    Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
    85a8ce62
buffer.c 90.5 KB