i2c: mpc: Avoid out of bounds memory access
When performing an I2C transfer where the last message was a write KASAN
would complain:
BUG: KASAN: slab-out-of-bounds in mpc_i2c_do_action+0x154/0x630
Read of size 2 at addr
c814e310 by task swapper/2/0
CPU: 2 PID: 0 Comm: swapper/2 Tainted: G B 5.16.0-rc8 #1
Call Trace:
[
e5ee9d50] [
c08418e8] dump_stack_lvl+0x4c/0x6c (unreliable)
[
e5ee9d70] [
c02f8a14] print_address_description.constprop.13+0x64/0x3b0
[
e5ee9da0] [
c02f9030] kasan_report+0x1f0/0x204
[
e5ee9de0] [
c0c76ee4] mpc_i2c_do_action+0x154/0x630
[
e5ee9e30] [
c0c782c4] mpc_i2c_isr+0x164/0x240
[
e5ee9e60] [
c00f3a04] __handle_irq_event_percpu+0xf4/0x3b0
[
e5ee9ec0] [
c00f3d40] handle_irq_event_percpu+0x80/0x110
[
e5ee9f40] [
c00f3e48] handle_irq_event+0x78/0xd0
[
e5ee9f60] [
c00fcfec] handle_fasteoi_irq+0x19c/0x370
[
e5ee9fa0] [
c00f1d84] generic_handle_irq+0x54/0x80
[
e5ee9fc0] [
c0006b54] __do_irq+0x64/0x200
[
e5ee9ff0] [
c0007958] __do_IRQ+0xe8/0x1c0
[
c812dd50] [
e3eaab20] 0xe3eaab20
[
c812dd90] [
c0007a4c] do_IRQ+0x1c/0x30
[
c812dda0] [
c0000c04] ExternalInput+0x144/0x160
--- interrupt: 500 at arch_cpu_idle+0x34/0x60
NIP:
c000b684 LR:
c000b684 CTR:
c0019688
REGS:
c812ddb0 TRAP: 0500 Tainted: G B (5.16.0-rc8)
MSR:
00029002 <CE,EE,ME> CR:
22000488 XER:
20000000
GPR00:
c10ef7fc c812de90 c80ff200 c2394718 00000001 00000001 c10e3f90 00000003
GPR08:
00000000 c0019688 c2394718 fc7d625b 22000484 00000000 21e17000 c208228c
GPR16:
e3e99284 00000000 ffffffff c2390000 c001bac0 c2082288 c812df60 c001ba60
GPR24:
c23949c0 00000018 00080000 00000004 c80ff200 00000002 c2348ee4 c2394718
NIP [
c000b684] arch_cpu_idle+0x34/0x60
LR [
c000b684] arch_cpu_idle+0x34/0x60
--- interrupt: 500
[
c812de90] [
c10e3f90] rcu_eqs_enter.isra.60+0xc0/0x110 (unreliable)
[
c812deb0] [
c10ef7fc] default_idle_call+0xbc/0x230
[
c812dee0] [
c00af0e8] do_idle+0x1c8/0x200
[
c812df10] [
c00af3c0] cpu_startup_entry+0x20/0x30
[
c812df20] [
c001e010] start_secondary+0x5d0/0xba0
[
c812dff0] [
c00028a0] __secondary_start+0x90/0xdc
This happened because we would overrun the i2c->msgs array on the final
interrupt for the I2C STOP. This didn't happen if the last message was a
read because there is no interrupt in that case. Ensure that we only
access the current message if we are not processing a I2C STOP
condition.
Fixes:
1538d82f4647 ("i2c: mpc: Interrupt driven transfer")
Reported-by: Maxime Bizon <mbizon@freebox.fr>
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Signed-off-by: Wolfram Sang <wsa@kernel.org>
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