From ec48a1d981fe90ecb5bcfaaf1ae2c69d842cbbbc Mon Sep 17 00:00:00 2001 From: Suzuki K Poulose Date: Tue, 14 Jun 2016 11:17:12 -0600 Subject: [PATCH] coresight: Fix NULL pointer dereference in _coresight_build_path _coresight_build_path assumes that all the connections of a csdev has the child_dev initialised. This may not be true if the particular component is not supported by the kernel config(e.g TPIU) but is present in the DT. In which case, building a path can cause a crash like this : Unable to handle kernel NULL pointer dereference at virtual address 00000010 pgd = ffffffc9750dd000 [00000010] *pgd=00000009f5e90003, *pud=00000009f5e90003, *pmd=0000000000000000 Internal error: Oops: 96000006 [#1] PREEMPT SMP Modules linked in: CPU: 4 PID: 1348 Comm: bash Not tainted 4.6.0-next-20160517 #1646 Hardware name: ARM Juno development board (r0) (DT) task: ffffffc97517a280 ti: ffffffc9762c4000 task.ti: ffffffc9762c4000 PC is at _coresight_build_path+0x18/0xe4 LR is at _coresight_build_path+0xc0/0xe4 pc : [] lr : [] pstate: 20000145 sp : ffffffc9762c7ba0 [] _coresight_build_path+0x18/0xe4 [] _coresight_build_path+0xc0/0xe4 [] _coresight_build_path+0xc0/0xe4 [] _coresight_build_path+0xc0/0xe4 [] _coresight_build_path+0xc0/0xe4 [] _coresight_build_path+0xc0/0xe4 [] coresight_build_path+0x40/0x68 [] coresight_enable+0x74/0x1bc [] enable_source_store+0x3c/0x6c [] dev_attr_store+0x18/0x28 [] sysfs_kf_write+0x40/0x50 [] kernfs_fop_write+0x140/0x1cc [] __vfs_write+0x28/0x110 [] vfs_write+0xa0/0x174 [] SyS_write+0x44/0xa0 [] el0_svc_naked+0x24/0x28 Cc: Mathieu Poirier Signed-off-by: Suzuki K Poulose Signed-off-by: Mathieu Poirier Signed-off-by: Greg Kroah-Hartman --- drivers/hwtracing/coresight/coresight.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/hwtracing/coresight/coresight.c b/drivers/hwtracing/coresight/coresight.c index 5443d03a1eec..0fdaaf4a8994 100644 --- a/drivers/hwtracing/coresight/coresight.c +++ b/drivers/hwtracing/coresight/coresight.c @@ -385,7 +385,6 @@ static int _coresight_build_path(struct coresight_device *csdev, int i; bool found = false; struct coresight_node *node; - struct coresight_connection *conn; /* An activated sink has been found. Enqueue the element */ if ((csdev->type == CORESIGHT_DEV_TYPE_SINK || @@ -394,8 +393,9 @@ static int _coresight_build_path(struct coresight_device *csdev, /* Not a sink - recursively explore each port found on this element */ for (i = 0; i < csdev->nr_outport; i++) { - conn = &csdev->conns[i]; - if (_coresight_build_path(conn->child_dev, path) == 0) { + struct coresight_device *child_dev = csdev->conns[i].child_dev; + + if (child_dev && _coresight_build_path(child_dev, path) == 0) { found = true; break; } -- 2.20.1