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From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Dan Williams <dan.j.williams@intel.com>,
	dmaengine@vger.kernel.org, Vinod Koul <vkoul@kernel.org>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Vladimir Murzin <vladimir.murzin@arm.com>
Subject: [PATCH v1 2/3] dmaengine: dmatest: Check list for emptiness before access its last entry
Date: Wed, 16 Sep 2020 16:34:55 +0300	[thread overview]
Message-ID: <20200916133456.79280-2-andriy.shevchenko@linux.intel.com> (raw)
In-Reply-To: <20200916133456.79280-1-andriy.shevchenko@linux.intel.com>

After writing a garbage to the channel we get an Oops in dmatest_chan_set()
due to access to last entry in the empty list.

[  212.670672] BUG: unable to handle page fault for address: fffffff000000020
[  212.677562] #PF: supervisor read access in kernel mode
[  212.682702] #PF: error_code(0x0000) - not-present page
...
[  212.710074] RIP: 0010:dmatest_chan_set+0x149/0x2d0 [dmatest]
[  212.715739] Code: e8 cc f9 ff ff 48 8b 1d 0d 55 00 00 48 83 7b 10 00 0f 84 63 01 00 00 48 c7 c7 d0 65 4d c0 e8 ee 4a f5 e1 48 89 c6 48 8b 43 10 <48> 8b 40 20 48 8b 78 58 48 85 ff 0f 84 f5 00 00 00 e8 b1 41 f5 e1

Fix this by checking list for emptiness before accessing its last entry.

Fixes: d53513d5dc28 ("dmaengine: dmatest: Add support for multi channel testing")
Cc: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---
 drivers/dma/dmatest.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/dma/dmatest.c b/drivers/dma/dmatest.c
index 4c9a9d7b48bb..757eb1727a04 100644
--- a/drivers/dma/dmatest.c
+++ b/drivers/dma/dmatest.c
@@ -1267,15 +1267,14 @@ static int dmatest_chan_set(const char *val, const struct kernel_param *kp)
 	add_threaded_test(info);
 
 	/* Check if channel was added successfully */
-	dtc = list_last_entry(&info->channels, struct dmatest_chan, node);
-
-	if (dtc->chan) {
+	if (!list_empty(&info->channels)) {
 		/*
 		 * if new channel was not successfully added, revert the
 		 * "test_channel" string to the name of the last successfully
 		 * added channel. exception for when users issues empty string
 		 * to channel parameter.
 		 */
+		dtc = list_last_entry(&info->channels, struct dmatest_chan, node);
 		if ((strcmp(dma_chan_name(dtc->chan), strim(test_channel)) != 0)
 		    && (strcmp("", strim(test_channel)) != 0)) {
 			ret = -EINVAL;
-- 
2.28.0


  reply	other threads:[~2020-09-16 20:35 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-16 13:34 [PATCH v1 1/3] dmaengine: dmatest: Fix regression when run command on misconfigured channel Andy Shevchenko
2020-09-16 13:34 ` Andy Shevchenko [this message]
2020-09-16 13:34 ` [PATCH v1 3/3] dmaengine: dmatest: Return boolean result directly in filter() Andy Shevchenko
2020-09-17  9:39   ` Peter Ujfalusi
2020-09-22 11:51     ` Andy Shevchenko
2020-09-17 10:30 ` [PATCH v1 1/3] dmaengine: dmatest: Fix regression when run command on misconfigured channel Vinod Koul
2020-09-22 11:47   ` Andy Shevchenko
2020-09-22 11:55     ` Andy Shevchenko

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