st_kim: Handle case of no device found for ID 0

From: Steven Rostedt
Date: Mon May 23 2011 - 16:45:41 EST

Running ktest.pl, I hit this bug:

[ 19.780654] BUG: unable to handle kernel NULL pointer dereference at 0000000c
[ 19.780660] IP: [<c112efcd>] dev_get_drvdata+0xc/0x46
[ 19.780669] *pdpt = 0000000031daf001 *pde = 0000000000000000
[ 19.780673] Oops: 0000 [#1] SMP
[ 19.780680] Dumping ftrace buffer:^M
[ 19.780685] (ftrace buffer empty)
[ 19.780687] Modules linked in: ide_pci_generic firewire_ohci firewire_core evbug crc_itu_t e1000 ide_core i2c_i801 iTCO_wdt
[ 19.780697]
[ 19.780700] Pid: 346, comm: v4l_id Not tainted 2.6.39-test-02740-gcaebc16-dirty #4 /DG965MQ
[ 19.780706] EIP: 0060:[<c112efcd>] EFLAGS: 00010202 CPU: 0
[ 19.780709] EIP is at dev_get_drvdata+0xc/0x46
[ 19.780712] EAX: 00000008 EBX: f1e37da4 ECX: 00000000 EDX: 00000000
[ 19.780715] ESI: f1c3f200 EDI: c33ec95c EBP: f1e37d80 ESP: f1e37d80
[ 19.780718] DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
[ 19.780721] Process v4l_id (pid: 346, ti=f1e36000 task=f2bc2a60 task.ti=f1e36000)
[ 19.780723] Stack:
[ 19.780725] f1e37d8c c117d395 c33ec93c f1e37db4 c117a0f9 00000002 00000000 c1725e54
[ 19.780732] 00000001 00000007 f2918c90 f1c3f200 c33ec95c f1e37dd4 c1789d3d 22222222
[ 19.780740] 22222222 22222222 f2918c90 f1c3f200 f29194f4 f1e37de8 c178d5c4 c1725e54
[ 19.780747] Call Trace:
[ 19.780752] [<c117d395>] st_kim_ref+0x28/0x41
[ 19.780756] [<c117a0f9>] st_register+0x29/0x562
[ 19.780761] [<c1725e54>] ? v4l2_open+0x111/0x1e3
[ 19.780766] [<c1789d3d>] fmc_prepare+0x97/0x424
[ 19.780770] [<c178d5c4>] fm_v4l2_fops_open+0x70/0x106
[ 19.780773] [<c1725e54>] ? v4l2_open+0x111/0x1e3
[ 19.780777] [<c1725e9b>] v4l2_open+0x158/0x1e3
[ 19.780782] [<c065173b>] chrdev_open+0x22c/0x276
[ 19.780787] [<c0647c4e>] __dentry_open+0x35c/0x581
[ 19.780792] [<c06498f9>] nameidata_to_filp+0x7c/0x96
[ 19.780795] [<c065150f>] ? cdev_put+0x57/0x57
[ 19.780800] [<c0660cad>] do_last+0x743/0x9d4
[ 19.780804] [<c065d5fc>] ? path_init+0x1ee/0x596
[ 19.780808] [<c0661481>] path_openat+0x10c/0x597
[ 19.780813] [<c05204a1>] ? trace_hardirqs_off+0x27/0x37
[ 19.780817] [<c0509651>] ? local_clock+0x78/0xc7
[ 19.780821] [<c0661945>] do_filp_open+0x39/0xc2
[ 19.780827] [<c1cabc76>] ? _raw_spin_unlock+0x4c/0x5d^M
[ 19.780831] [<c0674ccd>] ? alloc_fd+0x19e/0x1b7
[ 19.780836] [<c06499ca>] do_sys_open+0xb7/0x1bd
[ 19.780840] [<c0608eea>] ? sys_munmap+0x78/0x8d
[ 19.780844] [<c0649b06>] sys_open+0x36/0x58
[ 19.780849] [<c1cb809f>] sysenter_do_call+0x12/0x38
[ 19.780852] Code: d8 2f 20 c3 01 83 15 dc 2f 20 c3 00 f0 ff 00 83 05 e0 2f 20 c3 01 83 15 e4 2f 20 c3 00 5d c3 55 89 e5 3e 8d 74 26 00 85 c0 74 28 <8b> 40 04 83 05 e8 2f 20 c3 01 83 15 ec 2f 20 c3 00 85 c0 74 13 ^M
[ 19.780889] EIP: [<c112efcd>] dev_get_drvdata+0xc/0x46 SS:ESP 0068:f1e37d80
[ 19.780894] CR2: 000000000000000c
[ 19.780898] ---[ end trace e7d1d0f6a2d1d390 ]---

The id of 0 passed to st_kim_ref() found no device, keeping pdev null,
and causing pdev->dev cause a NULL pointer dereference. After having
st_kim_ref() check for NULL, the st_unregister() function needed to be
updated to handle the case that st_gdata was not set by the
st_kim_ref().

Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>


---
drivers/misc/ti-st/st_core.c | 2 +-
drivers/misc/ti-st/st_kim.c | 4 ++++
2 files changed, 5 insertions(+), 1 deletion(-)

Index: linux-test.git/drivers/misc/ti-st/st_core.c
===================================================================
--- linux-test.git.orig/drivers/misc/ti-st/st_core.c 2011-05-23 15:30:37.287951016 -0400
+++ linux-test.git/drivers/misc/ti-st/st_core.c 2011-05-23 16:04:40.422367907 -0400
@@ -605,7 +605,7 @@ long st_unregister(struct st_proto_s *pr
pr_debug("%s: %d ", __func__, proto->chnl_id);

st_kim_ref(&st_gdata, 0);
- if (proto->chnl_id >= ST_MAX_CHANNELS) {
+ if (!st_gdata || proto->chnl_id >= ST_MAX_CHANNELS) {
pr_err(" chnl_id %d not supported", proto->chnl_id);
return -EPROTONOSUPPORT;
}
Index: linux-test.git/drivers/misc/ti-st/st_kim.c
===================================================================
--- linux-test.git.orig/drivers/misc/ti-st/st_kim.c 2011-05-23 15:30:37.303951943 -0400
+++ linux-test.git/drivers/misc/ti-st/st_kim.c 2011-05-23 16:04:40.434368603 -0400
@@ -604,6 +604,10 @@ void st_kim_ref(struct st_data_s **core_
struct kim_data_s *kim_gdata;
/* get kim_gdata reference from platform device */
pdev = st_get_plat_device(id);
+ if (!pdev) {
+ *core_data = NULL;
+ return;
+ }
kim_gdata = dev_get_drvdata(&pdev->dev);
*core_data = kim_gdata->core_data;
}


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