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/ashrdi3.c | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+) create mode 100644 lib/ashrdi3.c (limited to 'lib/ashrdi3.c') diff --git a/lib/ashrdi3.c b/lib/ashrdi3.c new file mode 100644 index 000000000..fc84244ad --- /dev/null +++ b/lib/ashrdi3.c @@ -0,0 +1,34 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + */ + +#include + +#include + +long long notrace __ashrdi3(long long u, word_type b) +{ + DWunion uu, w; + word_type bm; + + if (b == 0) + return u; + + uu.ll = u; + bm = 32 - b; + + if (bm <= 0) { + /* w.s.high = 1..1 or 0..0 */ + w.s.high = + uu.s.high >> 31; + w.s.low = uu.s.high >> -bm; + } else { + const unsigned int carries = (unsigned int) uu.s.high << bm; + + w.s.high = uu.s.high >> b; + w.s.low = ((unsigned int) uu.s.low >> b) | carries; + } + + return w.ll; +} +EXPORT_SYMBOL(__ashrdi3); -- cgit v1.3.1