Hi all,

These patches fix a small out-of-bounds write when using the
nvmem-reboot-mode driver on Qualcomm SA8775P, such as by executing
"reboot bootloader" in a shell. Relevant error log:

  BUG: KASAN: slab-out-of-bounds in nvmem_cell_prepare_write_buffer+0x144/0x47c
  Write of size 4 at addr ffff19dd8e1a37a0 by task systemd-shutdow/1
  Hardware name: Qualcomm SA8775P Ride (DT)
  Call trace:
  nvmem_cell_prepare_write_buffer
  nvmem_cell_write
  nvmem_reboot_mode_write
  The buggy address is located 0 bytes inside of
   allocated 1-byte region

This problem manifested because the devicetree file sa8775p-pmics.dtsi
specifies its reboot-mode cell with "reg = <0x48 0x1>" and so expects
the reboot mode write to only be 1 byte rather than 4. Other in-tree
devicetrees that seem likely affected include pmk8350 and pmk8550.

These changes add the missing bounds check to nvmem_cell_write and make
nvmem-reboot-mode able to only write as many bytes as it needs to.

v2:
- Added missing function definition for CONFIG_NVMEM=n

v3:
- Accepted suggestion for changing nvmem_cell_write bounds check

---
Jennifer Berringer (3):
  nvmem: core: improve range check for nvmem_cell_write()
  nvmem: core: add nvmem_cell_write_variable_u32()
  power: reset: nvmem-reboot-mode: fix write for small cells

 drivers/nvmem/core.c                    | 26 +++++++++++++++++++++++++
 drivers/power/reset/nvmem-reboot-mode.c |  2 +-
 include/linux/nvmem-consumer.h          |  6 ++++++
 3 files changed, 33 insertions(+), 1 deletion(-)


base-commit: 98f7e32f20d28ec452afb208f9cffc08448a2652
-- 
2.46.2