• Rik van Riel's avatar
    blk-iocost: avoid out of bounds shift · beaa51b3
    Rik van Riel authored
    UBSAN catches undefined behavior in blk-iocost, where sometimes
    iocg->delay is shifted right by a number that is too large,
    resulting in undefined behavior on some architectures.
    
    [  186.556576] ------------[ cut here ]------------
    UBSAN: shift-out-of-bounds in block/blk-iocost.c:1366:23
    shift exponent 64 is too large for 64-bit type 'u64' (aka 'unsigned long long')
    CPU: 16 PID: 0 Comm: swapper/16 Tainted: G S          E    N 6.9.0-0_fbk700_debug_rc2_kbuilder_0_gc85af715 #1
    Hardware name: Quanta Twin Lakes MP/Twin Lakes Passive MP, BIOS F09_3A23 12/08/2020
    Call Trace:
     <IRQ>
     dump_stack_lvl+0x8f/0xe0
     __ubsan_handle_shift_out_of_bounds+0x22c/0x280
     iocg_kick_delay+0x30b/0x310
     ioc_timer_fn+0x2fb/0x1f80
     __run_timer_base+0x1b6/0x250
    ...
    
    Avoid that undefined behavior by simply taking the
    "delay = 0" branch if the shift is too large.
    
    I am not sure what the symptoms of an undefined value
    delay will be, but I suspect it could be more than a
    little annoying to debug.
    Signed-off-by: default avatarRik van Riel <riel@surriel.com>
    Cc: Tejun Heo <tj@kernel.org>
    Cc: Josef Bacik <josef@toxicpanda.com>
    Cc: Jens Axboe <axboe@kernel.dk>
    Acked-by: default avatarTejun Heo <tj@kernel.org>
    Link: https://lore.kernel.org/r/20240404123253.0f58010f@imladris.surriel.comSigned-off-by: default avatarJens Axboe <axboe@kernel.dk>
    beaa51b3
blk-iocost.c 98.4 KB