From: Andy Shevchenko andriy.shevchenko@linux.intel.com
[ Upstream commit b28de385b71abf31ce68ec0387638bee26ae9024 ]
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 Tested-by: Peter Ujfalusi peter.ujfalusi@ti.com Link: https://lore.kernel.org/r/20200922115847.30100-2-andriy.shevchenko@linux.int... Signed-off-by: Vinod Koul vkoul@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 62d9825a49e9d..238936e2dfe2d 100644 --- a/drivers/dma/dmatest.c +++ b/drivers/dma/dmatest.c @@ -1218,15 +1218,14 @@ 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;