From e873c74132f0c5f1452816cd9bb26208f0bba1e1 Mon Sep 17 00:00:00 2001 From: Shivank Garg Date: Sat, 22 Aug 2026 19:22:05 +0000 Subject: dmaengine: fix use-after-free in dma_chan_put() and dma_release_channel() When dma_device_put() drops the last reference on chan->device->ref, dma_device_release() runs and may free the dma_device along with its channels. dma_chan_put() then still reads chan->device->owner via dma_chan_to_owner() for the trailing module_put(). KASAN catches it: slab-use-after-free in dma_chan_put+0x3e6/0x4c0 Read of size 8 by task insmod/6319 Freed by task 6319: kfree+0x225/0x470 dma_chan_put+0x395/0x4c0 dmaengine_put+0xf8/0x160 Cache the module owner in dma_chan_put() before the put so the trailing module_put() does not need chan->device. Fixes: 8ad342a86359 ("dmaengine: Add reference counting to dma_device struct") Suggested-by: Sashiko Link: https://sashiko.dev/#/patchset/20260518-dmaengine-kref-fix-v1-1-4d6125048fb7@amd.com Reviewed-by: Frank Li Reviewed-by: Logan Gunthorpe Signed-off-by: Shivank Garg Link: https://patch.msgid.link/20260822-dmaengine-kref-fix-v5-3-d4a4ee47d927@amd.com Signed-off-by: Vinod Koul --- Documentation/admin-guide/device-mapper/delay.rst | 54 +++++++++++++++++++++++ 1 file changed, 54 insertions(+) create mode 100644 Documentation/admin-guide/device-mapper/delay.rst (limited to 'Documentation/admin-guide/device-mapper/delay.rst') diff --git a/Documentation/admin-guide/device-mapper/delay.rst b/Documentation/admin-guide/device-mapper/delay.rst new file mode 100644 index 000000000..a1e673c0e --- /dev/null +++ b/Documentation/admin-guide/device-mapper/delay.rst @@ -0,0 +1,54 @@ +======== +dm-delay +======== + +Device-Mapper's "delay" target delays reads and/or writes +and/or flushes and optionally maps them to different devices. + +Arguments:: + + [ + [ ]] + +Table line has to either have 3, 6 or 9 arguments: + +3: apply offset and delay to read, write and flush operations on device + +6: apply offset and delay to device, also apply write_offset and write_delay + to write and flush operations on optionally different write_device with + optionally different sector offset + +9: same as 6 arguments plus define flush_offset and flush_delay explicitly + on/with optionally different flush_device/flush_offset. + +Offsets are specified in sectors. + +Delays are specified in milliseconds. + + +Example scripts +=============== + +:: + #!/bin/sh + # + # Create mapped device named "delayed" delaying read, write and flush operations for 500ms. + # + dmsetup create delayed --table "0 `blockdev --getsz $1` delay $1 0 500" + +:: + #!/bin/sh + # + # Create mapped device delaying write and flush operations for 400ms and + # splitting reads to device $1 but writes and flushes to different device $2 + # to different offsets of 2048 and 4096 sectors respectively. + # + dmsetup create delayed --table "0 `blockdev --getsz $1` delay $1 2048 0 $2 4096 400" + +:: + #!/bin/sh + # + # Create mapped device delaying reads for 50ms, writes for 100ms and flushes for 333ms + # onto the same backing device at offset 0 sectors. + # + dmsetup create delayed --table "0 `blockdev --getsz $1` delay $1 0 50 $2 0 100 $1 0 333" -- cgit v1.3.1