• Konstantin Ovsepian's avatar
    blk_iocost: fix more out of bound shifts · 9bce8005
    Konstantin Ovsepian authored
    Recently running UBSAN caught few out of bound shifts in the
    ioc_forgive_debts() function:
    
    UBSAN: shift-out-of-bounds in block/blk-iocost.c:2142:38
    shift exponent 80 is too large for 64-bit type 'u64' (aka 'unsigned long
    long')
    ...
    UBSAN: shift-out-of-bounds in block/blk-iocost.c:2144:30
    shift exponent 80 is too large for 64-bit type 'u64' (aka 'unsigned long
    long')
    ...
    Call Trace:
    <IRQ>
    dump_stack_lvl+0xca/0x130
    __ubsan_handle_shift_out_of_bounds+0x22c/0x280
    ? __lock_acquire+0x6441/0x7c10
    ioc_timer_fn+0x6cec/0x7750
    ? blk_iocost_init+0x720/0x720
    ? call_timer_fn+0x5d/0x470
    call_timer_fn+0xfa/0x470
    ? blk_iocost_init+0x720/0x720
    __run_timer_base+0x519/0x700
    ...
    
    Actual impact of this issue was not identified but I propose to fix the
    undefined behaviour.
    The proposed fix to prevent those out of bound shifts consist of
    precalculating exponent before using it the shift operations by taking
    min value from the actual exponent and maximum possible number of bits.
    Reported-by: default avatarBreno Leitao <leitao@debian.org>
    Signed-off-by: default avatarKonstantin Ovsepian <ovs@ovs.to>
    Acked-by: default avatarTejun Heo <tj@kernel.org>
    Link: https://lore.kernel.org/r/20240822154137.2627818-1-ovs@ovs.toSigned-off-by: default avatarJens Axboe <axboe@kernel.dk>
    9bce8005
blk-iocost.c 98.5 KB