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 --- lib/cmpdi2.c | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) create mode 100644 lib/cmpdi2.c (limited to 'lib/cmpdi2.c') diff --git a/lib/cmpdi2.c b/lib/cmpdi2.c new file mode 100644 index 000000000..f7cebd52b --- /dev/null +++ b/lib/cmpdi2.c @@ -0,0 +1,30 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + */ + +#include + +#include + +word_type notrace __cmpdi2(long long a, long long b) +{ + const DWunion au = { + .ll = a + }; + const DWunion bu = { + .ll = b + }; + + if (au.s.high < bu.s.high) + return 0; + else if (au.s.high > bu.s.high) + return 2; + + if ((unsigned int) au.s.low < (unsigned int) bu.s.low) + return 0; + else if ((unsigned int) au.s.low > (unsigned int) bu.s.low) + return 2; + + return 1; +} +EXPORT_SYMBOL(__cmpdi2); -- cgit v1.3.1