[PATCH] i2c: smbus: fix NULL function pointer dereference

Baruch Siach
2024-04-10T15:13:19Z

Running i2cdetect on i2c slave device (i2c-designware) gives this splat:

[ 53.306730] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
[ 53.318340] Mem abort info:
[ 53.323864] ESR = 0x0000000086000004
[ 53.330374] EC = 0x21: IABT (current EL), IL = 32 bits
[ 53.338446] SET = 0, FnV = 0
[ 53.344263] EA = 0, S1PTW = 0
[ 53.350166] FSC = 0x04: level 0 translation fault
[ 53.357806] user pgtable: 4k pages, 48-bit VAs, pgdp=00000008c7d8e000
[ 53.367008] [0000000000000000] pgd=0000000000000000, p4d=0000000000000000
[ 53.376559] Internal error: Oops: 0000000086000004 [#1] PREEMPT SMP
[ 53.382892] Modules linked in:
[ 53.385936] CPU: 6 PID: 420 Comm: i2cdetect Not tainted 6.9.0-rc3-yocto-standard+ #1295
[ 53.393926] Hardware name: xxx (DT)
[ 53.398531] pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[ 53.405480] pc : 0x0
[ 53.407656] lr : __i2c_transfer+0x1f4/0x830
[ 53.411834] sp : ffff800082c13b00
[ 53.415136] x29: ffff800082c13b00 x28: 0000000000000001 x27: 0000000000000001
[ 53.422259] x26: ffff8000813aa340 x25: ffff0000c69553c0 x24: 00000000ffff0eeb
[ 53.429383] x23: ffff8000813a6000 x22: ffff800082c13bc0 x21: 0000000000000000
[ 53.436506] x20: 0000000000000001 x19: ffff000040b82140 x18: 0000000000000000
[ 53.443630] x17: 0000000000000000 x16: 0000000000000000 x15: 0000ffffff59bd58
[ 53.450753] x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000
[ 53.457876] x11: 0000000000000000 x10: 0000000000000000 x9 : ffff8000807e4470
[ 53.464999] x8 : ffff800082c13c05 x7 : 0000000000000001 x6 : ffff800082c13d56
[ 53.472122] x5 : 0000000000000001 x4 : 0000000000000000 x3 : 0000000000000000
[ 53.479245] x2 : 0000000000000001 x1 : ffff800082c13bc0 x0 : ffff000040b82140
[ 53.486368] Call trace:
[ 53.488803] 0x0
[ 53.490629] i2c_smbus_xfer_emulated+0x148/0x6d0
[ 53.495236] __i2c_smbus_xfer+0x130/0x4d0
[ 53.499235] i2c_smbus_xfer+0xc0/0x128
[ 53.502973] i2cdev_ioctl_smbus+0x110/0x2b0
[ 53.507145] i2cdev_ioctl+0x9c/0x348
[ 53.510710] __arm64_sys_ioctl+0xb4/0xe0
[ 53.514624] invoke_syscall+0x4c/0x118
[ 53.518365] el0_svc_common.constprop.0+0xc4/0xf0
[ 53.523058] do_el0_svc+0x24/0x38
[ 53.526362] el0_svc+0x28/0xb8
[ 53.529407] el0t_64_sync_handler+0x134/0x150
[ 53.533751] el0t_64_sync+0x14c/0x150
[ 53.537405] Code: ???????? ???????? ???????? ???????? (????????)
[ 53.543485] ---[ end trace 0000000000000000 ]---

Callers of __i2c_transfer() must verify that master_xfer is not NULL.
Check that before i2c_smbus_xfer_emulated() call.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
---
drivers/i2c/i2c-core-smbus.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/i2c-core-smbus.c b/drivers/i2c/i2c-core-smbus.c
index e3b96fc53b5c..d252716c9f74 100644
--- a/drivers/i2c/i2c-core-smbus.c
+++ b/drivers/i2c/i2c-core-smbus.c
@@ -604,8 +604,11 @@ s32 __i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr,
*/
}

- res = i2c_smbus_xfer_emulated(adapter, addr, flags, read_write,
- command, protocol, data);
+ if (adapter->algo->master_xfer)
+ res = i2c_smbus_xfer_emulated(adapter, addr, flags, read_write,
+ command, protocol, data);
+ else
+ res = -EOPNOTSUPP;

trace:
/* If enabled, the reply tracepoint is conditional on read_write. */
--
2.43.0