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/blockdev/nbd.rst | 31 ++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) create mode 100644 Documentation/admin-guide/blockdev/nbd.rst (limited to 'Documentation/admin-guide/blockdev/nbd.rst') diff --git a/Documentation/admin-guide/blockdev/nbd.rst b/Documentation/admin-guide/blockdev/nbd.rst new file mode 100644 index 000000000..faf2ac4b1 --- /dev/null +++ b/Documentation/admin-guide/blockdev/nbd.rst @@ -0,0 +1,31 @@ +================================== +Network Block Device (TCP version) +================================== + +1) Overview +----------- + +What is it: With this compiled in the kernel (or as a module), Linux +can use a remote server as one of its block devices. So every time +the client computer wants to read, e.g., /dev/nb0, it sends a +request over TCP to the server, which will reply with the data read. +This can be used for stations with low disk space (or even diskless) +to borrow disk space from another computer. +Unlike NFS, it is possible to put any filesystem on it, etc. + +For more information, or to download the nbd-client and nbd-server +tools, go to https://github.com/NetworkBlockDevice/nbd. + +The nbd kernel module need only be installed on the client +system, as the nbd-server is completely in userspace. In fact, +the nbd-server has been successfully ported to other operating +systems, including Windows. + +A) NBD parameters +----------------- + +max_part + Number of partitions per device (default: 0). + +nbds_max + Number of block devices that should be initialized (default: 16). -- cgit v1.3.1