scsi: target: tcmu: Fix crash on ARM during cmd completion

If tcmu_handle_completions() has to process a padding shorter than
sizeof(struct tcmu_cmd_entry), the current call to
tcmu_flush_dcache_range() with sizeof(struct tcmu_cmd_entry) as length
param is wrong and causes crashes on e.g. ARM, because
tcmu_flush_dcache_range() in this case calls
flush_dcache_page(vmalloc_to_page(start)); with start being an invalid
address above the end of the vmalloc'ed area.

The fix is to use the minimum of remaining ring space and sizeof(struct
tcmu_cmd_entry) as the length param.

The patch was tested on kernel 4.19.118.

See https://bugzilla.kernel.org/show_bug.cgi?id=208045#c10

Link: https://lore.kernel.org/r/[email protected]
Tested-by: JiangYu <[email protected]>
Acked-by: Mike Christie <[email protected]>
Signed-off-by: Bodo Stroesser <[email protected]>
Signed-off-by: Martin K. Petersen <[email protected]>

0 files changed, 0 insertions, 0 deletions