Re: [PATCH] i2c: iproc: fix race between client unreg and isr

[Scott Branden]

looks good.

On 2020-07-19 12:59 a.m., Rayagonda Kokatanur wrote:
> On Sun, Jul 19, 2020 at 5:10 AM Dhananjay Phadke
> <dphadke@xxxxxxxxxxxxxxxxxxx> wrote:
> > When i2c client unregisters, synchronize irq before setting
> > iproc_i2c->slave to NULL.
> >
> > Unable to handle kernel NULL pointer dereference at virtual address 0000000000000318
> >
> > [  371.020421] pc : bcm_iproc_i2c_isr+0x530/0x11f0
> > [  371.025098] lr : __handle_irq_event_percpu+0x6c/0x170
> > [  371.030309] sp : ffff800010003e40
> > [  371.033727] x29: ffff800010003e40 x28: 0000000000000060
> > [  371.039206] x27: ffff800010ca9de0 x26: ffff800010f895df
> > [  371.044686] x25: ffff800010f18888 x24: ffff0008f7ff3600
> > [  371.050165] x23: 0000000000000003 x22: 0000000001600000
> > [  371.055645] x21: ffff800010f18888 x20: 0000000001600000
> > [  371.061124] x19: ffff0008f726f080 x18: 0000000000000000
> > [  371.066603] x17: 0000000000000000 x16: 0000000000000000
> > [  371.072082] x15: 0000000000000000 x14: 0000000000000000
> > [  371.077561] x13: 0000000000000000 x12: 0000000000000001
> > [  371.083040] x11: 0000000000000000 x10: 0000000000000040
> > [  371.088519] x9 : ffff800010f317c8 x8 : ffff800010f317c0
> > [  371.093999] x7 : ffff0008f805b3b0 x6 : 0000000000000000
> > [  371.099478] x5 : ffff0008f7ff36a4 x4 : ffff8008ee43d000
> > [  371.104957] x3 : 0000000000000000 x2 : ffff8000107d64c0
> > [  371.110436] x1 : 00000000c00000af x0 : 0000000000000000
> >
> > [  371.115916] Call trace:
> > [  371.118439]  bcm_iproc_i2c_isr+0x530/0x11f0
> > [  371.122754]  __handle_irq_event_percpu+0x6c/0x170
> > [  371.127606]  handle_irq_event_percpu+0x34/0x88
> > [  371.132189]  handle_irq_event+0x40/0x120
> > [  371.136234]  handle_fasteoi_irq+0xcc/0x1a0
> > [  371.140459]  generic_handle_irq+0x24/0x38
> > [  371.144594]  __handle_domain_irq+0x60/0xb8
> > [  371.148820]  gic_handle_irq+0xc0/0x158
> > [  371.152687]  el1_irq+0xb8/0x140
> > [  371.155927]  arch_cpu_idle+0x10/0x18
> > [  371.159615]  do_idle+0x204/0x290
> > [  371.162943]  cpu_startup_entry+0x24/0x60
> > [  371.166990]  rest_init+0xb0/0xbc
> > [  371.170322]  arch_call_rest_init+0xc/0x14
> > [  371.174458]  start_kernel+0x404/0x430
> >
> > Fixes: c245d94ed106 ("i2c: iproc: Add multi byte read-write support for slave mode")
> > Signed-off-by: Dhananjay Phadke <dphadke@xxxxxxxxxxxxxxxxxxx>
Acked-by: Scott Branden <scott.branden@xxxxxxxxxxxx>
> > ---
> >   drivers/i2c/busses/i2c-bcm-iproc.c | 5 +++--
> >   1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/i2c/busses/i2c-bcm-iproc.c b/drivers/i2c/busses/i2c-bcm-iproc.c
> > index b58224b7b..37d2a79e7 100644
> > --- a/drivers/i2c/busses/i2c-bcm-iproc.c
> > +++ b/drivers/i2c/busses/i2c-bcm-iproc.c
> > @@ -1074,14 +1074,15 @@ static int bcm_iproc_i2c_unreg_slave(struct i2c_client *slave)
> >          if (!iproc_i2c->slave)
> >                  return -EINVAL;
> >
> > -       iproc_i2c->slave = NULL;
> > -
> >          /* disable all slave interrupts */
> >          tmp = iproc_i2c_rd_reg(iproc_i2c, IE_OFFSET);
> >          tmp &= ~(IE_S_ALL_INTERRUPT_MASK <<
> >                          IE_S_ALL_INTERRUPT_SHIFT);
> >          iproc_i2c_wr_reg(iproc_i2c, IE_OFFSET, tmp);
> >
> > +       synchronize_irq(iproc_i2c->irq);
> > +       iproc_i2c->slave = NULL;
> > +
> >          /* Erase the slave address programmed */
> >          tmp = iproc_i2c_rd_reg(iproc_i2c, S_CFG_SMBUS_ADDR_OFFSET);
> >          tmp &= ~BIT(S_CFG_EN_NIC_SMB_ADDR3_SHIFT);
> Looks good to me. Thank you for the patch.
> Reviewed-by: Rayagonda Kokatanur <rayagonda.kokatanur@xxxxxxxxxxxx>
>
> Regards,
> Rayagonda