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dmaengine: dmatest: Check list for emptiness before access its last entry
[ Upstream commitb28de385b7
] 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:d53513d5dc
("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> Tested-by: Peter Ujfalusi <peter.ujfalusi@ti.com> Link: https://lore.kernel.org/r/20200922115847.30100-2-andriy.shevchenko@linux.intel.com Signed-off-by: Vinod Koul <vkoul@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
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1 changed files with 2 additions and 3 deletions
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@ -1218,15 +1218,14 @@ static int dmatest_chan_set(const char *val, const struct kernel_param *kp)
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add_threaded_test(info);
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/* Check if channel was added successfully */
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dtc = list_last_entry(&info->channels, struct dmatest_chan, node);
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if (dtc->chan) {
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if (!list_empty(&info->channels)) {
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/*
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* if new channel was not successfully added, revert the
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* "test_channel" string to the name of the last successfully
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* added channel. exception for when users issues empty string
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* to channel parameter.
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*/
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dtc = list_last_entry(&info->channels, struct dmatest_chan, node);
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if ((strcmp(dma_chan_name(dtc->chan), strim(test_channel)) != 0)
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&& (strcmp("", strim(test_channel)) != 0)) {
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ret = -EINVAL;
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