• Shuicheng Lin's avatar
    drm/xe: Fix UBSAN shift-out-of-bounds failure · 205e5c4b
    Shuicheng Lin authored
    Here is the failure stack:
    [   12.988209] ------------[ cut here ]------------
    [   12.988216] UBSAN: shift-out-of-bounds in ./include/linux/log2.h:57:13
    [   12.988232] shift exponent 64 is too large for 64-bit type 'long unsigned int'
    [   12.988235] CPU: 4 PID: 1310 Comm: gnome-shell Tainted: G     U             6.9.0-rc6+prerelease1158+ #19
    [   12.988237] Hardware name: Intel Corporation Raptor Lake Client Platform/RPL-S ADP-S DDR5 UDIMM CRB, BIOS RPLSFWI1.R00.3301.A02.2208050712 08/05/2022
    [   12.988239] Call Trace:
    [   12.988240]  <TASK>
    [   12.988242]  dump_stack_lvl+0xd7/0xf0
    [   12.988248]  dump_stack+0x10/0x20
    [   12.988250]  ubsan_epilogue+0x9/0x40
    [   12.988253]  __ubsan_handle_shift_out_of_bounds+0x10e/0x170
    [   12.988260]  dma_resv_reserve_fences.cold+0x2b/0x48
    [   12.988262]  ? ww_mutex_lock_interruptible+0x3c/0x110
    [   12.988267]  drm_exec_prepare_obj+0x45/0x60 [drm_exec]
    [   12.988271]  ? vm_bind_ioctl_ops_execute+0x5b/0x740 [xe]
    [   12.988345]  vm_bind_ioctl_ops_execute+0x78/0x740 [xe]
    
    It is caused by the value 0 of parameter num_fences in function
    drm_exec_prepare_obj.  And lead to in function __rounddown_pow_of_two,
    "0 - 1" causes the shift-out-of-bounds.
    
    By design drm_exec_prepare_obj() should be called only when there are
    fences to be reserved. If num_fences is 0, calling drm_exec_lock_obj()
    is sufficient as was done in commit 9377de4c ("drm/xe/vm: Avoid
    reserving zero fences")
    
    Cc: Nirmoy Das <nirmoy.das@intel.com>
    Cc: Matthew Brost <matthew.brost@intel.com>
    Signed-off-by: default avatarShuicheng Lin <shuicheng.lin@intel.com>
    Reviewed-by: default avatarNirmoy Das <nirmoy.das@intel.com>
    Link: https://lore.kernel.org/all/24d4a9a9-c622-4f56-8672-21f4c6785476@amd.com
    Link: https://patchwork.freedesktop.org/patch/msgid/20240507130411.630361-1-shuicheng.lin@intel.comSigned-off-by: default avatarLucas De Marchi <lucas.demarchi@intel.com>
    205e5c4b
xe_vm.c 85.1 KB