Change the memcpy length to fix the out-of-bounds issue when writing the
data that is not 4 byte aligned to TX FIFO.

To reproduce the issue, write 3 bytes data to NOR chip.

dd if=3b of=/dev/mtd0
[   36.926103] ==================================================================
[   36.933409] BUG: KASAN: slab-out-of-bounds in nxp_fspi_exec_op+0x26ec/0x2838
[   36.940514] Read of size 4 at addr ffff00081037c2a0 by task dd/455
[   36.946721]
[   36.948235] CPU: 3 UID: 0 PID: 455 Comm: dd Not tainted 6.11.0-rc5-gc7b0e37c8434 #1070
[   36.956185] Hardware name: Freescale i.MX8QM MEK (DT)
[   36.961260] Call trace:
[   36.963723]  dump_backtrace+0x90/0xe8
[   36.967414]  show_stack+0x18/0x24
[   36.970749]  dump_stack_lvl+0x78/0x90
[   36.974451]  print_report+0x114/0x5cc
[   36.978151]  kasan_report+0xa4/0xf0
[   36.981670]  __asan_report_load_n_noabort+0x1c/0x28
[   36.986587]  nxp_fspi_exec_op+0x26ec/0x2838
[   36.990800]  spi_mem_exec_op+0x8ec/0xd30
[   36.994762]  spi_mem_no_dirmap_read+0x190/0x1e0
[   36.999323]  spi_mem_dirmap_write+0x238/0x32c
[   37.003710]  spi_nor_write_data+0x220/0x374
[   37.007932]  spi_nor_write+0x110/0x2e8
[   37.011711]  mtd_write_oob_std+0x154/0x1f0
[   37.015838]  mtd_write_oob+0x104/0x1d0
[   37.019617]  mtd_write+0xb8/0x12c
[   37.022953]  mtdchar_write+0x224/0x47c
[   37.026732]  vfs_write+0x1e4/0x8c8
[   37.030163]  ksys_write+0xec/0x1d0
[   37.033586]  __arm64_sys_write+0x6c/0x9c
[   37.037539]  invoke_syscall+0x6c/0x258
[   37.041327]  el0_svc_common.constprop.0+0x160/0x22c
[   37.046244]  do_el0_svc+0x44/0x5c
[   37.049589]  el0_svc+0x38/0x78
[   37.052681]  el0t_64_sync_handler+0x13c/0x158
[   37.057077]  el0t_64_sync+0x190/0x194
[   37.060775]
[   37.062274] Allocated by task 455:
[   37.065701]  kasan_save_stack+0x2c/0x54
[   37.069570]  kasan_save_track+0x20/0x3c
[   37.073438]  kasan_save_alloc_info+0x40/0x54
[   37.077736]  __kasan_kmalloc+0xa0/0xb8
[   37.081515]  __kmalloc_noprof+0x158/0x2f8
[   37.085563]  mtd_kmalloc_up_to+0x120/0x154
[   37.089690]  mtdchar_write+0x130/0x47c
[   37.093469]  vfs_write+0x1e4/0x8c8
[   37.096901]  ksys_write+0xec/0x1d0
[   37.100332]  __arm64_sys_write+0x6c/0x9c
[   37.104287]  invoke_syscall+0x6c/0x258
[   37.108064]  el0_svc_common.constprop.0+0x160/0x22c
[   37.112972]  do_el0_svc+0x44/0x5c
[   37.116319]  el0_svc+0x38/0x78
[   37.119401]  el0t_64_sync_handler+0x13c/0x158
[   37.123788]  el0t_64_sync+0x190/0x194
[   37.127474]
[   37.128977] The buggy address belongs to the object at ffff00081037c2a0
[   37.128977]  which belongs to the cache kmalloc-8 of size 8
[   37.141177] The buggy address is located 0 bytes inside of
[   37.141177]  allocated 3-byte region [ffff00081037c2a0, ffff00081037c2a3)
[   37.153465]
[   37.154971] The buggy address belongs to the physical page:
[   37.160559] page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x89037c
[   37.168596] flags: 0xbfffe0000000000(node=0|zone=2|lastcpupid=0x1ffff)
[   37.175149] page_type: 0xfdffffff(slab)
[   37.179021] raw: 0bfffe0000000000 ffff000800002500 dead000000000122 0000000000000000
[   37.186788] raw: 0000000000000000 0000000080800080 00000001fdffffff 0000000000000000
[   37.194553] page dumped because: kasan: bad access detected
[   37.200144]
[   37.201647] Memory state around the buggy address:
[   37.206460]  ffff00081037c180: fa fc fc fc fa fc fc fc fa fc fc fc fa fc fc fc
[   37.213701]  ffff00081037c200: fa fc fc fc 05 fc fc fc 03 fc fc fc 02 fc fc fc
[   37.220946] >ffff00081037c280: 06 fc fc fc 03 fc fc fc fc fc fc fc fc fc fc fc
[   37.228186]                                ^
[   37.232473]  ffff00081037c300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[   37.239718]  ffff00081037c380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[   37.246962] ==================================================================
[   37.254394] Disabling lock debugging due to kernel taint
0+1 records in
0+1 records out
3 bytes copied, 0.335911 s, 0.0 kB/s

Fixes: a5356aef ("spi: spi-mem: Add driver for NXP FlexSPI controller")
Cc: stable@kernel.org
Signed-off-by: Han Xu <han.xu@nxp.com>
Link: https://patch.msgid.link/20240911211146.3337068-1-han.xu@nxp.comSigned-off-by: Mark Brown <broonie@kernel.org>