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Subject[PATCH v2] spi: fsl-dspi: fix NULL pointer dereference
Date
Since commit 530b5affc675 ("spi: fsl-dspi: fix use-after-free in remove
path") this driver causes a kernel oops:

[ 1.891065] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000080
[ 1.899889] Mem abort info:
[ 1.902692] ESR = 0x96000004
[ 1.905754] EC = 0x25: DABT (current EL), IL = 32 bits
[ 1.911089] SET = 0, FnV = 0
[ 1.914156] EA = 0, S1PTW = 0
[ 1.917303] Data abort info:
[ 1.920193] ISV = 0, ISS = 0x00000004
[ 1.924044] CM = 0, WnR = 0
[ 1.927022] [0000000000000080] user address but active_mm is swapper
[ 1.933403] Internal error: Oops: 96000004 [#1] PREEMPT SMP
[ 1.938995] Modules linked in:
[ 1.942060] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.9.0-rc6-next-20200925-00026-gae556cc74e28-dirty #94
[ 1.951838] Hardware name: Kontron SMARC-sAL28 (Single PHY) on SMARC Eval 2.0 carrier (DT)
[ 1.960135] pstate: 40000005 (nZcv daif -PAN -UAO -TCO BTYPE=--)
[ 1.966168] pc : dspi_setup+0xc8/0x2e0
[ 1.969926] lr : dspi_setup+0xbc/0x2e0
[ 1.973684] sp : ffff80001139b930
[ 1.977005] x29: ffff80001139b930 x28: ffff00207a5d2000
[ 1.982338] x27: 0000000000000006 x26: ffff00207a44d410
[ 1.987669] x25: ffff002079c08100 x24: ffff00207a5d2400
[ 1.993000] x23: ffff00207a5d2600 x22: ffff800011169948
[ 1.998332] x21: ffff800010cbcd20 x20: ffff00207a58a800
[ 2.003663] x19: ffff00207a76b700 x18: 0000000000000010
[ 2.008994] x17: 0000000000000001 x16: 0000000000000019
[ 2.014326] x15: ffffffffffffffff x14: 0720072007200720
[ 2.019657] x13: 0720072007200720 x12: ffff8000111fc5e0
[ 2.024989] x11: 0000000000000003 x10: ffff8000111e45a0
[ 2.030320] x9 : 0000000000000000 x8 : ffff00207a76b780
[ 2.035651] x7 : 0000000000000000 x6 : 000000000000003f
[ 2.040982] x5 : 0000000000000040 x4 : ffff80001139b918
[ 2.046313] x3 : 0000000000000001 x2 : 64b62cc917af5100
[ 2.051643] x1 : 0000000000000000 x0 : 0000000000000000
[ 2.056973] Call trace:
[ 2.059425] dspi_setup+0xc8/0x2e0
[ 2.062837] spi_setup+0xcc/0x248
[ 2.066160] spi_add_device+0xb4/0x198
[ 2.069918] of_register_spi_device+0x250/0x370
[ 2.074462] spi_register_controller+0x4f4/0x770
[ 2.079094] dspi_probe+0x5bc/0x7b0
[ 2.082594] platform_drv_probe+0x5c/0xb0
[ 2.086615] really_probe+0xec/0x3c0
[ 2.090200] driver_probe_device+0x60/0xc0
[ 2.094308] device_driver_attach+0x7c/0x88
[ 2.098503] __driver_attach+0x60/0xe8
[ 2.102263] bus_for_each_dev+0x7c/0xd0
[ 2.106109] driver_attach+0x2c/0x38
[ 2.109692] bus_add_driver+0x194/0x1f8
[ 2.113538] driver_register+0x6c/0x128
[ 2.117385] __platform_driver_register+0x50/0x60
[ 2.122105] fsl_dspi_driver_init+0x24/0x30
[ 2.126302] do_one_initcall+0x54/0x2d0
[ 2.130149] kernel_init_freeable+0x1ec/0x258
[ 2.134520] kernel_init+0x1c/0x120
[ 2.138018] ret_from_fork+0x10/0x34
[ 2.141606] Code: 97e0b11d aa0003f3 b4000680 f94006e0 (f9404000)
[ 2.147723] ---[ end trace 26cf63e6cbba33a8 ]---
[ 2.152374] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
[ 2.160061] SMP: stopping secondary CPUs
[ 2.163999] Kernel Offset: disabled
[ 2.167496] CPU features: 0x0040022,20006008
[ 2.171777] Memory Limit: none
[ 2.174840] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b ]---

This is because since this commit, the allocation of the drivers private
data is done explicitly and in this case spi_alloc_master() won't set the
correct pointer.

Also move the platform_set_drvdata() to have both next to each other.

Fixes: 530b5affc675 ("spi: fsl-dspi: fix use-after-free in remove path")
Signed-off-by: Michael Walle <michael@walle.cc>
Tested-by: Sascha Hauer <s.hauer@pengutronix.de>
---

changes since v1:
- moved platform_set_drvdata(), suggested by Krzysztof.

drivers/spi/spi-fsl-dspi.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/spi/spi-fsl-dspi.c b/drivers/spi/spi-fsl-dspi.c
index a939618f5e47..3967afa465f0 100644
--- a/drivers/spi/spi-fsl-dspi.c
+++ b/drivers/spi/spi-fsl-dspi.c
@@ -1236,6 +1236,9 @@ static int dspi_probe(struct platform_device *pdev)
if (!ctlr)
return -ENOMEM;

+ spi_controller_set_devdata(ctlr, dspi);
+ platform_set_drvdata(pdev, dspi);
+
dspi->pdev = pdev;
dspi->ctlr = ctlr;

@@ -1371,8 +1374,6 @@ static int dspi_probe(struct platform_device *pdev)
if (dspi->devtype_data->trans_mode != DSPI_DMA_MODE)
ctlr->ptp_sts_supported = true;

- platform_set_drvdata(pdev, dspi);
-
ret = spi_register_controller(ctlr);
if (ret != 0) {
dev_err(&pdev->dev, "Problem registering DSPI ctlr\n");
--
2.20.1
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